scholar study guide cfe higher human biology …acknowledgements thanks are due to the members of...

SCHOLAR Study Guide

CfE Higher Human BiologyUnit 3: Neurobiology andCommunication

Authored by:Eoin McIntyre (Previously Auchmuty High School)

Reviewed by:Sheena Haddow (Perth College)

Previously authored by:Mike Cheung

Eileen Humphrey

Eoin McIntyre

Jim McIntyre

Heriot-Watt University

Edinburgh EH14 4AS, United Kingdom.

First published 2014 by Heriot-Watt University.

This edition published in 2016 by Heriot-Watt University SCHOLAR.

Copyright © 2016 SCHOLAR Forum.

Members of the SCHOLAR Forum may reproduce this publication in whole or in part foreducational purposes within their establishment providing that no profit accrues at any stage,Any other use of the materials is governed by the general copyright statement that follows.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval systemor transmitted in any form or by any means, without written permission from the publisher.

Heriot-Watt University accepts no responsibility or liability whatsoever with regard to theinformation contained in this study guide.

Distributed by the SCHOLAR Forum.

SCHOLAR Study Guide Unit 3: CfE Higher Human Biology

1. CfE Higher Human Biology Course Code: C740 76

ISBN 978-1-909633-18-6

Print Production and Fulfilment in UK by Print Trail www.printtrail.com

AcknowledgementsThanks are due to the members of Heriot-Watt University’s SCHOLAR team who planned andcreated these materials, and to the many colleagues who reviewed the content.

We would like to acknowledge the assistance of the education authorities, colleges, teachersand students who contributed to the SCHOLAR programme and who evaluated these materials.

Grateful acknowledgement is made for permission to use the following material in theSCHOLAR programme:

The Scottish Qualifications Authority for permission to use Past Papers assessments.

The Scottish Government for financial support.

The content of this Study Guide is aligned to the Scottish Qualifications Authority (SQA)curriculum.

All brand names, product names, logos and related devices are used for identification purposesonly and are trademarks, registered trademarks or service marks of their respective holders.

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Contents

1 The structure of the nervous system 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Divisions of the nervous system . . . . . . . . . . . . . . . . . . . . . . 41.3 Parts of the brain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.4 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211.5 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . 231.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2 Perception and memory 292.1 Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302.2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402.3 A note about techniques . . . . . . . . . . . . . . . . . . . . . . . . . . 502.4 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512.5 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . 542.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

3 Neurons, neurotransmitters and neural pathways 593.1 Neurons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.2 Glial cells and myelination . . . . . . . . . . . . . . . . . . . . . . . . . 693.3 Neurotransmitters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 723.4 Neural pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773.5 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833.6 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . 853.7 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

4 Neurotransmitters, mood and behaviour 914.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 924.2 Dopamine and the reward pathway . . . . . . . . . . . . . . . . . . . . 934.3 Endorphins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 944.4 Neurotransmitter-related disorders and their treatment . . . . . . . . . 954.5 Mode of action of recreational drugs . . . . . . . . . . . . . . . . . . . 1004.6 Drug addiction, sensitisation and tolerance . . . . . . . . . . . . . . . . 1034.7 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1054.8 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . 1064.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

5 Infant attachment and the effect of communication 1095.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1105.2 Forms of infant attachment . . . . . . . . . . . . . . . . . . . . . . . . . 1125.3 Long period of dependency . . . . . . . . . . . . . . . . . . . . . . . . 117

ii CONTENTS

5.4 The effect of communication . . . . . . . . . . . . . . . . . . . . . . . . 1195.5 Non-verbal communication . . . . . . . . . . . . . . . . . . . . . . . . . 1205.6 Verbal communication . . . . . . . . . . . . . . . . . . . . . . . . . . . 1235.7 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1275.8 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . 1285.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

6 The effect of experience and social influences 1316.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1326.2 The effect of practice on motor skills . . . . . . . . . . . . . . . . . . . 1326.3 Imitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1336.4 Trial and error learning . . . . . . . . . . . . . . . . . . . . . . . . . . . 1356.5 Generalisation and discrimination . . . . . . . . . . . . . . . . . . . . . 1376.6 Social facilitation and deindividuation . . . . . . . . . . . . . . . . . . . 1396.7 Influences that change beliefs . . . . . . . . . . . . . . . . . . . . . . . 1416.8 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1426.9 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . 1436.10 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

7 End of unit test 145

Glossary 149

Answers to questions and activities 1561 The structure of the nervous system . . . . . . . . . . . . . . . . . . . 1562 Perception and memory . . . . . . . . . . . . . . . . . . . . . . . . . . 1623 Neurons, neurotransmitters and neural pathways . . . . . . . . . . . . 1684 Neurotransmitters, mood and behaviour . . . . . . . . . . . . . . . . . 1745 Infant attachment and the effect of communication . . . . . . . . . . . 1806 The effect of experience and social influences . . . . . . . . . . . . . . 1847 End of unit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

© HERIOT-WATT UNIVERSITY

1

Topic 1

The structure of the nervoussystem

Contents

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2 Divisions of the nervous system . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2.1 Central and peripheral nervous systems . . . . . . . . . . . . . . . . . . 5

1.2.2 Autonomic nervous system . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.3 Parts of the brain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.3.1 The central core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.3.2 The limbic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.3.3 The cerebral cortex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.4 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

1.5 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

1.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Learning objectives

By the end of this topic, you should be able to:

• explain the general functions of the nervous system;

• describe the different divisions of the nervous system and their specific functions;

• describe the basic structure of the brain;

• state the functions of the central core, the limbic system and the cerebral cortex.

2 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM

1.1 Introduction�

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Learning objective

By the end of this section, you should be able to:

• state that the nervous system contains three types of neuron: sensory, motorand interneurons;

• state that sensory neurons connect sense receptors with the central nervoussystem;

• state that motor neurons connect the central nervous system to muscles orglands;

• state that interneurons may connect with sensory, motor or other interneurons;

• state that the nervous system analyses sensory information from both theexternal and internal environment;

• explain that the body stores some of this information which it uses to makedecisions about appropriate responses and behaviours;

• state that motor responses may be made by initiating muscular contractions orglandular secretions.

Animals show two basic types of symmetry: radial symmetry, where there is an upperand lower side, but no front or back, e.g. jellyfish; and bilateral symmetry, where thereare not only upper and lower surfaces, but a front and back as well, e.g. worms andvertebrates. In the latter types of animal, there is usually a distinct ’head’, or part of thebody which meets the world first, on which most external sense organs are clustered.

Sense organs are structures that contain receptors which respond to stimuli. Thesestimuli can be changes in the external environment, which are detected as differenttypes of energy (e.g. light, sound, chemical, kinetic and heat), or changes in the internalenvironment, e.g. changes in core temperature or the carbon dioxide level in the blood.To be of any use, this information must be assessed and appropriate action taken inresponse. This is done by neurons, of which there are three broad classes:

• sensory neurons, which connect sense receptors to the central nervous system;

• motor neurons, which connect the central nervous system to the muscles andglands;

• interneurons (also known as relay, association or connector neurons), which arefound in the central nervous system and connect with sensory, motor, and otherinterneurons.

When stimulated, neurons pass along their length a temporary reversal of the electricalpotential on their plasma membrane. These are called impulses and travel at velocitiesbetween 1 and 100 m.s-1. By locating many sense organs in the head and developingthe processing area of the central nervous system close to them, rates of reaction toincoming stimuli can be maximised. The grouping of interneurons in the same area,to form a brain, allows more interconnections and more complex processing, such as


TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 3

learning and memory.

The extent to which learning plays an important part in animal behaviour depends verymuch on the type of animal involved. Insects, which live for only a short period, maynever see their parents and only interact with others of their own species to mate.Consequently, they rely almost entirely on inherited, innate patterns of behaviour toidentify food, escape predators, and find mates and places to lay eggs. There is no timefor insects to learn these things which means that the environment will weed out the lesssuccessful life strategies by natural selection.

Long-lived animals, such as Primates (including humans), are social creatures with along dependent period, which means that there is ample opportunity for them to developresponses which are based on their own experience and on the observation of others(although it would be a mistake to think that innate responses play no role in Primatebehaviour).

Interestingly, the same type of behaviour may be innate in one group but learned inothers, e.g. mothering behaviour: a crocodile reared in isolation will still show the carefulattention to her young which is typical of the species, whereas chimpanzees (normallythe most attentive of mothers) when reared in isolation are most likely to reject theiroffspring.

In summary, the nervous system provides animals with the means to collect, analyseand respond appropriately to sensory information. These motor responses may take theform of muscular contractions (e.g. reflexes such as knee-jerks or blinks) or secretionsfrom glands (e.g. adrenal or salivary glands).

Introduction to the structure of the nervous system: Questions

Go online

Q1: Sensory neurons connect sense organs to

a) the central nervous systemb) motor neuronsc) sensory neurons

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Q2: Motor neurons connect the central nervous system to

a) interneuronsb) muscles and glandsc) sense organs

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Q3: Interneurons are located in

a) the central nervous systemb) musclesc) sense organs

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Q4: Secretions by the adrenal gland are stimulated by

a) interneuronsb) motor neuronsc) sensory neurons

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Q5: Storage of information is carried out by

a) interneuronsb) motor neuronsc) sensory neurons

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1.2 Divisions of the nervous system�

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Learning objective


• state that the nervous system is divided into the central and peripheral nervoussystems;

• state that the central nervous system comprises the brain and spinal cord;

• state that the peripheral nervous system is divided into the somatic andautonomic nervous systems;

• state that the autonomic nervous system is further subdivided into thesympathetic and the parasympathetic nervous systems.

The nervous system is sub-divided according to its structures and their functions.



Divisions of the nervous system: Question

Go online

Q6: Complete the labelling of the diagram using the words from the list.

Word list : autonomic, central, parasympathetic, peripheral, spinal cord.

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1.2.1 Central and peripheral nervous systems�

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Learning objective


• state that the central nervous system consists of the spinal cord and the brain,including the retinas of the eyes and the optic nerves;

• state that the peripheral nervous system comprises all sensory and motorneurons outside the central nervous system;

• state that the peripheral nervous system comprises the somatic and autonomicnervous systems;

• state that the somatic nervous system controls the voluntary movement ofskeletal muscles;

• explain that this control involves sensory neurons (e.g. connected to stretchreceptors in striped/striated muscle in leg) and motor neurons;

• state that the autonomic nervous system is responsible for involuntaryhomeostatic control of many body functions;

• explain that this control involves sensory neurons (e.g. connected to stretchreceptors in smooth muscle of artery walls) and motor neurons;

• state that the motor neurons of the autonomic nervous system may connect tosmooth muscle (e.g. in the wall of the gut), cardiac muscle (e.g. pacemaker) orglands (e.g. adrenal gland).

Scientists distinguish between the central nervous system (CNS) and the peripheralnervous system (PNS). The CNS comprises the brain, including the retinas of the eyesand optic nerves, and spinal cord, whereas the PNS consists of all the other parts, suchas the sensory and motor neurons. This is a purely structural division.



Central and peripheral nervous systems

The PNS is further divided functionally into the somatic and autonomic nervoussystems.

Somatic nerves control voluntary movement by controlling skeletal muscles. Theyinclude sensory neurons and motor neurons. Sensory neurons send messages tothe CNS from the sensory receptors, mainly in the skin, whereas motor neurons takemessages to the muscles or glands causing them to function.

The autonomic system tends to control our basic activities, the ones that do not tend torequire conscious thought. You do not have to command,

"O heart, beat faster! I see my teacher yonder."

The autonomic system controls heart rate without conscious thought.

Nor do you need to decide to breathe faster when your homework is late. Heart rate,breathing, peristalsis, and other similar functions are under the control of the autonomicnervous system. Muscles under voluntary control have a striped (striated) appearancelike the fibres of a steak, whereas muscles under autonomic control are un-striped andreferred to as ’smooth muscle’. Cardiac muscle, which must never tire, appears like across between striated muscle and the smooth muscle of the alimentary canal andblood vessels.



The autonomic nervous system also controls endocrine glands which regulate growthand the activities of other tissues. These include the pituitary, thyroid, pancreas andadrenal glands.

Endocrine glands

Go online5 min

Pituitary gland : sometimes called the master gland, the pituitary secretes manyhormones, e.g. growth hormone and ADH.It also secretes hormones which control the activity of the other endocrine glands, e.g.thyroid stimulationg hormone (TSH) stimulates the thyroid gland.

Thyroid gland : When stimulated by TSH from the pituitary, the thyroid gland secretesthe hormone thyroxine which regulates an individual’s metabolic rate.

Parathyroid glands: these secrete parathyroid hormone, which regulates the level ofcalcium in the blood.

Adrenal glands: the adrenal glands are situated on the upper surface of each kidney (ad= at, renal = kidney).They secrete many hormones the most well-known probably being adrenalin.This hormone is involved in the ’fight or flight’ mechanism which is triggered in responseto danger.

Ovary : found in females, ovaries produce the hormones oestrogen and progesteronewhen stimulated by hormones from the pituitary gland.



The interplay between these hormones controls the menstrual cycle, including thematuration and release of an ovum and the build up and break down of the lining ofthe uterus.Oestrogen also has a role in the development and maintenance of the female secondarysexual characteristics.

Testis: found in males, testes produce hormones such as testosterone when stimulatedby hormones form the pituitary gland.Testosterone is involved in the production of sperm and development and maintenanceof male secondary sexual characteristics.

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1.2.2 Autonomic nervous system�

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Learning objective


• state that the autonomic nervous system (ANS) comprises the sympathetic andparasympathetic nervous systems;

• state that the sympathetic and parasympathetic nervous systems actantagonistically;

• state that the sympathetic nervous system prepares the body for action: ’fightor flight’;

• state that the parasympathetic nervous system returns the body to a relaxed,standby condition: ’rest and digest’;

• state that the sympathetic nervous system causes increases in heart andbreathing rates, and decreases in peristalsis and intestinal secretions;

• state that the parasympathetic system causes decreases in heart and breathingrates, and increases in peristalsis and intestinal secretions.

The two branches of the autonomic nervous system, the sympathetic and theparasympathetic, can be thought of as alert, ’fight or flight’, and standby, ’rest anddigest’, modes respectively. The former prepares the body for action and the latterreturns the organism to an energy-conserving state. Thus, the sympathetic andparasympathetic nervous systems are described as antagonistic in action. This enablesthe ANS to exert homeostatic control over many of the body’s functions. This isclearly observed in their effects on heart rate, breathing rate, peristalsis and intestinalsecretions.



Function Sympathetic nervesspeed up - prepare for action

Parasympathetic nervescalm down - conserve resources

Heartrate

Rate and force of contraction ofcardiac muscle increases.Result: more blood to muscles.

Rate and force of contraction ofcardiac muscle decreases.Result: less blood to muscles,normal levels restored.

Breathingrate

Muscles in bronchioles becomerelaxed. Rate of contraction ofdiaphragm and intercostal musclesincreases.Result: increased gas exchange.

Muscles in bronchioles becomecontracted. Rate of contraction ofdiaphragm and intercostalmuscles decreases.Result: reduced gas exchange.

Digestion

Rate of contraction of smoothmuscle in wall of digestive tractdecreases. Rate of blood flow todigestive tract decreases.Result: reduced digestion.

Rate of contraction of smoothmuscle in wall of digestive tractincreases. Rate of blood flow todigestive tract increases.Result: normal digestion.

Adrenalgland

Adrenal gland stimulated.Result: secretion of hormoneadrenaline.

Summary of the influences of the Sympathetic and Parasympathetic Nervous Systems

Sympathetic and parasympathetic effects

Go online5 min

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Autonomic nervous system: Question

Go online10 min

Q7: Enter either ’Increased’ or ’Decreased’ at the correct places in the table.

Sympathetic Parasympathetic

Heart rate

Stroke volume

Breathing rate

Depth of breathing

Contractions of smoothmuscle of gut wall

Intestinal secretions

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1.3 Parts of the brain�

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Learning objective


• state that the brain consists of three major regions: medulla, cerebellum andcerebrum;

• state that the cerebrum comprises two interconnected hemispheres.

The vertebrate brain is the enlarged fore-end of the spinal cord, adapted to managethe mass of sensory information coming in from the sense organs and the animal’sresponses to it. In humans, this adaptation is taken to an incredibly complex level, butthe ’primitive’ areas which run the body’s machinery at a subconscious level are stillpresent (and, of course, essential). As the accompanying activity shows, the brain isdivided into three main areas: the medulla, the cerebellum and the cerebrum (whichconsists of two interconnected cerebral hemispheres).

The human organism consists of several organ systems which function in acoordinated way to respond to stimuli in the environment. Each organ system consistsof organs which, in turn, comprise groups of tissues. Tissues are assemblies of cellswith common functions. Every freshly-produced cell contains a nucleus which has allthe instructions to allow it to perform all cellular functions. However, to ensure thatchaos does not ensue, each nucleus only activates the genes necessary for it toperform the functions of that tissue of which the cell is part.

Just as the nucleus controls cellular function, the nervous system coordinates organsystems. It works in tandem with the endocrine system, so that immediate responsescan be effected by nerves, whilst longer term responses and functions are managed byhormones. Sensations are also mediated by nerves.



While the major parts of the brain are interconnected, each can also be subdivided intoa great many areas dependent either on their cellular structure or their function. Thebasic layers with which we are concerned here are the central core, the limbic systemand the cerebral cortex.

Parts of the brain: Question

Go online5 min

Q8: Complete the labelling of the diagram using the words provided.

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1.3.1 The central core�

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Learning objective


• state that the central core comprises the medulla and the cerebellum;

• state that the medulla regulates breathing rate, heart rate, arousal and sleep;

• state that the cerebellum controls balance, muscular co-ordination, posture andmovement.

The central core, consisting of the medulla and the cerebellum, is an ancient partof the brain in that it does much the same in humans as it does in other mammals. Ittakes care of much of the housekeeping in the body that would be dangerous to leavea human in charge of. The medulla and the cerebellum are, however, very different inboth structure and function.



Medulla

The medulla, like the spinal cord, has the grey matter in the centre and the fattywhite matter on the outside. It is a key part of the autonomic nervous system and,through the sympathetic and parasympathetic neurons, it controls the heart rate set bythe pacemaker, or sino-atrial node (SAN). It also regulates breathing, in response toimpulses from the receptors that detect blood carbon dioxide concentrations, and bloodpressure, in response to the degree of stretch detected by receptors in the artery walls.Simple reflexes such as coughing, sneezing, swallowing and vomiting are controlled bythe medulla, as are alertness (arousal) and consciousness (sleep).

Cerebellum

The cerebellum, like the cerebrum, has the grey matter on its convoluted outer surface,while the white matter is contained internally. However, the way in which the neuronsinteract is totally different - deep thought is the last thing that is required of thecerebellum. Although consisting of only about one eighth of the total brain mass, itcontains as many neurons as the whole of the rest of the brain.

It is the cerebrum which initiates movement, but the cerebellum is responsible forits accurate timing, precision, and co-ordination. This is achieved by matching thecontraction of the antagonistic muscles involved; body posture is controlled in the sameway.

Maintaining balance is another of the cerebellum’s responsibilities; think of the range ofsensory information and muscular control that is needed to perform well on a skateboardand you will begin to understand what a sophisticated computer the cerebellum must be.

The central core: Question

Go online

Q9: Complete the table by putting the processes into their correct column.

Medulla Cerebellum

Processes: arousal, balance, breathing, movement, muscular coordination, posture,sleep, heart rate.

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1.3.2 The limbic system�

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Learning objective


• state that the limbic system is concerned with the formation of memories,influencing emotional and motivational states;

• state that the limbic system contains many parts, one of which is thehypothalamus which influences the pituitary by means of the secretion ofhormones;

• state that other parts of the limbic system regulate homeostasis by means ofthe autonomic nervous system, e.g. blood pressure by contraction/relaxation ofsmooth muscle in artery walls;

• state that the limbic system also regulates body temperature by means of theautonomic nervous system;

• state that the limbic system is also involved in the control of water balance bythe secretion of ADH.

The limbic system forms the inner border of the cerebrum and is not a single entity buta group of brain structures with quite diverse functions. Two in particular are mentionedbelow: the hippocampus and the hypothalamus. Overall, it is involved in the followingareas and exerts its effect by influencing the endocrine system and the autonomicnervous system.

a) Determines states of emotion and motivation. These are inter-related and actuallyquite difficult states of mind to define.

• Emotion - is associated with mood, temperament and personality, e.g. anger,desire, envy.

• Motivation - determines which behaviour will take place, how strongly it willbe expressed, and for how long.

b) Involved in the formation of long-term memories (in the hippocampusparticularly).

c) Influences the production of hormones by the pituitary gland, by itself releasinghormones from the hypothalamus which stimulate or inhibit pituitary activity.

d) Homeostatic regulation of:

• body core temperature around the set point of 37◦C, e.g. by causingvasodilation and vasoconstriction by relaxing and contracting the smoothmuscle in the walls of smaller arteries and arterioles serving the skin, plusa wide range of other mechanisms;

• blood pressure, by controlling the contraction/relaxation of the smooth muscleof arterial walls in response to impulses from their stretch receptors;

• water balance, through the production of antidiuretic hormone (ADH) in thehypothalamus, which is stored and released from the pituitary gland.



1.3.3 The cerebral cortex�

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Learning objective


• state that the cerebral cortex is the centre of conscious thought;

• state that the cerebral cortex receives sensory information, coordinatesvoluntary movement, makes decisions, recalls memories and alters behaviourin the light of experience;

• explain that functions are localised in the cerebral cortex into sensory areas,motor areas, and association areas;

• state that the association areas deal with thought processes, language,imagination and intelligence;

• state that the left cerebral hemisphere deals with information from the rightvisual field and the right side of the body, and vice versa;

• state that the cerebral hemispheres are connected by the corpus callosum,which allows transfer of information;

• state that the brain operates as an integrated whole.

The cerebral cortex is the thin outer layer of the cerebrum. Being intensely folded(convoluted), its large surface area maximises the number of interconnections possiblebetween neurons. It is 2-4mm thick and consists of grey matter which comprises thecell bodies of neurons and unmyelinated neurons (which lack a fatty myelin sheath).The inner layers of the cerebrum consist of white matter which is largely composed ofmyelinated axons connecting different parts of the cerebral cortex with each other andwith other parts of the nervous system. This arrangement is the same in the cerebellum,but is reversed in the medulla and the spinal cord.

Broadly, the cortex can be said to comprise three parts: the sensory, motor, andassociation areas. These reflect the evolutionary history of the cerebrum as the partof the brain which receives incoming information from the sense organs, appraises it,and sends out signals to the appropriate organs to make a response.

The modern human cerebral cortex is also the centre of conscious thought. Not onlydoes it receive sensory information, it coordinates voluntary movement (as opposed toreflexes), makes decisions, recalls memories and uses experience to modify behaviour(learning).

Sensory areas

The senses of vision, hearing, and touch are served by the visual cortex, auditory cortexand somatosensory cortex. On each hemisphere, the visual cortex is located at theback, the somatosensory cortex on either side, just to the rear of the midline, and theauditory cortex immediately below it. Other senses, such as taste and smell, also havelocalised areas which deal with them (and may include other parts of the brain).



Motor areas

The motor areas of each hemisphere are also located down the midline, immediately infront of the somatosensory areas. Both the somatosensory and motor cortices can besubdivided according to the parts of the body to which they relate, the size of each areareflecting the sensitivity and degree of fine motor control involved.

Until recently, knowledge of the functions of different parts of the brain was based onthe observed results of brain damage. A wide range of modern techniques, such aselectroencephalographs and brain scans, have allowed much more detailed analysis.

Electroencephalographs

Electroencephalographs (EEGs) show electrical activity in the brain.

Electroencephalographs of brain electrical activity

CAT scans

It is useful to compare patterns of activity using EEGs, especially when comparingnormal and abnormal brainwaves. However, these do not give good evidence oflocalisation of function.

A different brain scan called a CAT scan (Computer Assisted Tomography), showsmetabolic activity, providing better evidence for localisation of function. For example,while listening, metabolic activity in the areas of the brain involved in hearing can betraced.



CAT scans and brain activity

Go online10 min

The areas of brain activity when a subject is performing the following activities aresummarised in the following diagram:

1. hearing;

2. seeing;

3. speaking;

4. areas associated with particular activities.

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Unfortunately, CAT Scans and Electroencephalographs tell us little on their own.Observation of people who have suffered brain injuries and subsequent dissection oftheir brain tissue after death have provided much more evidence.

It seems that the brain has tissues allocated to receiving information from the senses(the somatosensory area, or simply the sensory area) and tissues sending instructionsto the muscles (the motor area) localised in adjacent parts of the cortex. The brain, infact, allocates the size of each area of sensation and control according to theimportance of the functions carried out. The more sophisticated the senses received,and the finer the control of the muscles, the more brain tissue is allocated.



Localisation of function: Motor and sensory humunculi

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A large part of the motor area is devoted to the hands and lips. This allows a finedegree of motor control. For example, fingers can hold an egg without crushing it ormanoeuvre a coin from finger to finger. Remember that the left motor cortex controlsthe right side of the body and vice versa.

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As shown in the activity above, there is a major organisation of tissues to enable easylinkage of sensory messages from a specific area of the body with the motor impulsesrequired to control these organs and tissues. The homunculus is a visual way ofexplaining this organisation. The somatosensory area receives information from cold,heat, pain, touch and kinaesthetic receptors in the skin. Thus, an impulse coming infrom a leg is sensed by neurons in the somatosensory area adjacent to the neurons ofthe motor area which direct the movement of that leg.

Large parts of the sensory area are devoted to the lips, fingers and sex organs, makingthem very sensitive. This explains why we kiss with the lips and why infants explorenew toys with their lips. Similarly, large parts of the motor area are devoted to thetongue and lips, allowing speech, and to the fingers, allowing fine manipulation.

The great apes also have fine control of lips and tongue, but, crucially, they lack a voicebox which we have evolved due to different selection pressures operating during ourevolution.



Association areas

At the simplest level, the association areas integrate sensory information from differentsensory areas and relate it to past experience. A decision is then made and neuronimpulses sent to the motor areas to give responses.

However, the association areas are also where the individual person resides, as they arethe location of thought processes, personality, imagination, language and intelligence.These are not easy concepts to define, and fortunately are not part of this syllabus. Butjust to whet the appetite, here are some suggestions:

• thought: mental activity of which we are aware and undertake deliberately, thatgenerates ideas and underlies almost all human actions;

• personality: the sum of an individual’s emotions, attitudes and behaviour;

• imagination: helps us to make sense of the world and learn, by allowing us to formvisual or sensory images without actually experiencing them at the same time;

• language: a system of signs, gestures or sounds which convey particularmeanings;

• intelligence: mental ability, either inborn or acquired, to pay attention, remember,process language, solve problems and make decisions; this is a very controversialtopic.

Association areas for speaking

Go online10 min

How different parts of the association area in the brain respond to written and spokenwords

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Left and right hemispheres

The cerebrum is divided into the left and right hemispheres. These are not independentstructures; they are linked by the corpus callosum which allows the transfer ofinformation between the hemispheres.

Although the hemispheres appear to duplicate many functions, there are importantdifferences.

A treatment for severe epilepsy involves cutting all or part of the corpus callosum inorder to isolate the two cerebral hemispheres. The subsequent behaviour of suchsplit-brain patients, in whom the two hemispheres cannot communicate properly, showsthat tasks are not evenly divided between the two hemispheres. Images appear to beprocessed by the left hemisphere in most people. Language and analytical skills are alsoprocessed here. The right hemisphere controls visuospatial tasks, such as recognisingfacial features and arranging objects or reading maps.

These findings have been corroborated by observation of subjects with trauma toparticular regions of the cerebrum.

Split-brain study

Go online10 min

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Despite the apparent localisation of function in many areas of the brain, it is also thecase that a great many functions involve the activity not just of different areas of thecerebral hemispheres, but also the other parts of the brain. The brain in fact operates asan integrated whole, but one which shows remarkable powers of flexibility in responseto damage, e.g. as a result of a stroke.



Limbic system and cerebral cortex: Question

Go online

Q10: Complete the table by putting words from the list below to correctly match thestatements about the limbic system and the cerebral cortex. Some items may be usedmore than once.

Process Area

Controls voluntary movement

Processes information for the formation ofmemories

Transfers information between hemispheres

Influences the secretions of the pituitary

Recalls memories

Deals with language and imagination

Receives impulses from the skin

Centre of conscious thought

Controls the left side of the body

Acts as an integrated whole

Word list : association area, brain, cerebral cortex, corpus callosum, hypothalamus,limbic system, motor area, right cerebral hemisphere, somatosensory area.

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1.4 Learning points

Summary

Introduction

• The nervous system contains three types of neuron, namely sensory, motorand interneurons.

• Sensory neurons connect sense receptors with the central nervous system.

• Motor neurons connect the central nervous system to muscles or glands.

• Interneurons may connect with sensory, motor or other interneurons.

• The nervous system analyses sensory information from both the externaland internal environment.

• The body stores some of this information and makes decisions aboutappropriate responses and behaviours.

• Motor responses may be made by initiating muscular contractions orglandular secretions.

Divisions of the nervous system

• The nervous system is divided into the central and peripheral nervoussystems.

• The central nervous system comprises the brain and spinal cord.

• The peripheral nervous system is divided into the somatic and autonomicnervous systems.

• The autonomic nervous system is further subdivided into the sympatheticand the parasympathetic nervous systems.

Central and peripheral nervous systems

• The central nervous system consists of the spinal cord and the brain,including the retinas of the eyes and the optic nerve.

• The peripheral nervous system comprises all sensory and motor neuronsoutside of the central nervous system.

• The peripheral nervous system comprises the somatic and autonomicnervous systems.

• The somatic nervous system controls the voluntary movement of skeletalmuscles.

• This control involves sensory neurons (e.g. connected to stretch receptorsin striped/striated muscle in leg) and motor neurons.

• The autonomic nervous system is responsible for involuntary homeostaticcontrol of many body functions.



Summary continued

• This control also involves sensory neurons (e.g. connected to stretchreceptors in smooth muscle of artery walls) and motor neurons.

• The motor neurons of the autonomic nervous system may connect tosmooth muscle (e.g. in the wall of the gut), cardiac muscle (e.g. pacemaker)or glands (e.g. adrenal gland).

Autonomic nervous system

• The autonomic nervous system comprises the sympathetic andparasympathetic nervous systems.

• The sympathetic and parasympathetic nervous systems actantagonistically.

• The sympathetic nervous system prepares the body for action: ’fight orflight’.

• The parasympathetic nervous system returns the body to a relaxed, standbycondition: ’rest and digest’.

• The sympathetic nervous system causes increases in heart and breathingrates, and decreases in peristalsis and intestinal secretions.

• The parasympathetic nervous system causes decreases in heart andbreathing rates, and increases in peristalsis and intestinal secretions.

Parts of the brain

• The brain consists of three major regions: medulla, cerebellum andcerebrum.

• The cerebrum comprises two interconnected hemispheres.

The central core

• The central core comprises the medulla and the cerebellum.

• The medulla regulates breathing rate, heart rate, arousal and sleep.

• The cerebellum controls balance, muscular co-ordination, posture andmovement.

The limbic system

• The limbic system is concerned with the formation of memories, influencingemotional and motivational states.

• The limbic system contains many parts, one of which is the hypothalamuswhich influences the pituitary through the secretion of hormones.

• Other parts of the limbic system regulate homeostasis by means of theautonomic nervous system, e.g. blood pressure by contraction/relaxationof smooth muscle in artery walls.



Summary continued

• The limbic system also regulates body temperature by means of theautonomic nervous system.

• The limbic system is also involved in the control of water balance by thesecretion of ADH.

The cerebral cortex

• The cerebral cortex is the centre of conscious thought.

• The cerebral cortex receives sensory information, coordinates voluntarymovement, makes decisions, recalls memories and alters behaviour in thelight of experience.

• Functions are localised in the cerebral cortex into sensory areas, motorareas, and association areas.

• The association areas deal with thought processes, language, imaginationand intelligence.

• The left cerebral hemisphere deals with information from the right visualfield and the right side of the body, and vice versa.

• The cerebral hemispheres are connected by the corpus callosum, whichallows transfer of information.

• The brain operates as an integrated whole.

1.5 Extended response question

The activity which follows presents an extended response question similar to the stylethat you will encounter in the examination.

You should have a good understanding of the nervous system before attempting thequestion.

You should give your completed answer to your teacher or tutor for marking, or try tomark it yourself using the suggested marking scheme.

Extended response question: Nervous system

15 min

Give an account of the nervous system under the headings:

A) divisions of the nervous system; (5 marks)

B) homeostatic control. (5 marks)

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1.6 End of topic test

End of Topic 1 test

Go online

Q11: Complete the sentences by matching the parts on the left with the parts on theright. (10 marks)

Types of neuron:autonomic nervoussystem.

Connect sense receptors to CNS: somatic and autonomic.

Connect CNS to muscles and glands: brain and spinal cord.

Connect to other neurons of all types: central and peripheral.

Analysis of information: sensory, motor,interneuron.

Muscular contractions and glandular secretions: sensory neurons.

Divisions of the nervous system: motor neurons.

Central nervous system comprises: central nervous system.

Divisions of the peripheral nervous system: interneurons.

Sympathetic and parasympathetic: motor responses.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Controls the voluntary movement of skeletal muscles: connect to smooth andcardiac muscle.

Skeletal muscle control by sensory and motorneurons is:

sensory and motorneurons.

Responsible for involuntary homeostatic control:sympathetic nervoussystem.

Involuntary homeostatic control involves:parasympathetic nervoussystem.

Motor neurons of the autonomic nervous system:autonomic nervoussystem.

Action of the sympathetic and parasympatheticnervous system:

voluntary.

Increases heart rate, decreases intestinal secretions: somatic nervous system.

Decreases breathing rate, increases peristalsis: antagonistic.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



The diagram shows the main parts of the brain in vertical section.

Q13: Identify the part labelled X. (1 mark)

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Q14: Identify the part labelled Z. (1 mark)

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Q15: To which part of the nervous system does the brain belong? (1 mark)

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Q16: The part labelled Y is the corpus callosum. What is its function? (1 mark)

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Q17: Identify the medulla in the diagram. (1 mark)

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Q18: State two functions regulated by the medulla. (2 marks)

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Q19: Name the part of the brain responsible for balance. (1 mark)

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The diagram shows the divisions of the nervous system.

Q20: Identify the part labelled A in the diagram. (1 mark)

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Q21: Identify the part labelled B in the diagram. (1 mark)

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Q22: Identify the part labelled C in the diagram. (1 mark)

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Q23: Identify the part labelled D in the diagram. (1 mark)

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Q24: Identify the part labelled E in the diagram. (1 mark)

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Q25: Homeostatic control is regulated by which structures within the autonomic nervoussystem? (1 mark)

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Q26: To which structures are impulses sent during the process of homeostatic control?(2 marks)

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Q27: State the effect of the parasympathetic nervous system on heart rate. (1 mark)

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Q28: State the effect of the parasympathetic nervous system on peristalsis. (1 mark)

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Q29: In which part of the brain is the hypothalamus located? (1 mark)

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Q30: How does the hypothalamus regulate the function of the pituitary? (1 mark)

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Q31: State two homeostatic mechanisms regulated by the hypothalamus. (2 marks)

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Q32: Which part of the cerebrum is the centre of conscious thought? (1 mark)

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Q33: Apart from the association areas, what are the two localised functional areas ofthe cerebrum? (1 mark)

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Q34: State three mental functions that are dealt with by the association areas. (3 marks)

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29

Topic 2

Perception and memory

Contents

2.1 Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.1.1 Segregation of objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.1.2 Perception of distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2.1.3 Recognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

2.2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

2.2.1 Sensory Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

2.2.2 Short-Term Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

2.2.3 Long-Term Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

2.2.4 Location of memory in the brain . . . . . . . . . . . . . . . . . . . . . . 48

2.3 A note about techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

2.4 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51


2.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Learning objectives


• define perception as the process by which sensory information is organised,identified and interpreted by the brain so that we can make sense of it;

• describe how we segregate and recognise objects;

• describe the different methods by which distance is perceived;

• define memory as the storage, retention and retrieval of information;

• describe the nature of sensory, short-term and long-term memory, and theirrelationship;

• describe the location of memory in the brain.

30 TOPIC 2. PERCEPTION AND MEMORY

2.1 Perception�

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Learning objective


• state that perception is the process by which the brain analyses and makessense of incoming sensory information;

• describe how perception allows us to segregate objects from one another andfrom their background;

• describe how perception allows us to judge the distance of objects;

• describe how perception allows us to recognise objects.

We are aware of our surrounding environment as a result of the physical stimulationof our sense organs. Thus, light is detected by the rods and cones of the retina,sound waves by the organs of Corti in the cochlea of the ears, kinetic energy bymechanoreceptors in the skin, and chemicals by chemoreceptors in the nose andmouth. These energy signals must be converted into nerve impulses before they can beprocessed by the nervous system, a process known as transduction.

In each eye we have some 7 million cones and 75-150 million rods connected to thebrain by a million nerve fibres in the optic nerve. If you look out of the window, youtake in the scene with all of its features, including perhaps trees, buildings, cars, people,grass and birds, but that is not what your retina detects. Its photoreceptors fire off animpulse in response to the light which they receive. It is the neurons in the retina, opticnerve and the visual cortex of the cerebrum which create the image we ’see’. Not onlydo they create a seamless picture for us from the individual nerve impulses (which are,of course, no different to any other impulses), but they organise and interpret this ’data’so that we do not see mere patches of brown, green, black and white, but objects suchas trees, roads, sheep and clouds.

This interpretation process depends on memory and an analysis of context; fluffy whiteobjects against a green background are likely to be sheep, but against a blue backgroundthey are more likely to be clouds. Sometimes, this process can be tripped up; if youhave ever been given a cup of tea when you were expecting coffee, especially whenengrossed in some other activity, you may have experienced that moment of confusionwhen you can almost hear the cogs turning in your brain. Your system first identifiesthe liquid as very strange coffee, and then takes a noticeable time before it correctlyrecognises it as tea.

It is necessary then to appreciate that what we consciously perceive is the product ofconsiderable mental processing, and not what is recorded by our sense organs.

Although the syllabus content is limited to the perception process related to vision, itapplies to all the senses. To you, the bass playing on a particular musical track may befantastic, but to your neighbour it may just be a loud noise because they do not have theexperience to separate the sound of the different instruments. Have you added too muchcumin to the curry? Unless they know their spices, nobody will notice. The word ’object’can therefore be used in a general way to refer to the sound of a specific instrument ora particular flavour.


TOPIC 2. PERCEPTION AND MEMORY 31

2.1.1 Segregation of objects�

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Learning objective


• explain that the brain organises sensory information into figures (objects) andgrounds (background) during perception;

• explain that, in order to make sense of our environment, the brain organisessensory stimuli into coherent patterns during perception.

Figure and ground

All but the simplest of animals use the information from their sense organs to avoidpredators and to find the essentials of life, such as food, mates, shelter, and water. Todo this, they must distinguish the properties of these objects from amongst the mass ofincoming stimuli so there must be a reference memory against which the information canbe matched. Mammals gain much of this information by means of learning, especiallyfrom the parents. Other types of animal, e.g. most fish and insects, never meet theirparents and so most of this information must be inherited genetically rather than passedon by social contact or learned by trial and error.

In terms of the sense of sight, this process involves trying to identify known shapeswithin what we are seeing. This involves identifying the shape against its surroundingbackground which involves segregating the figure from the ground. The best knownexample of this is Edgar Rubin’s vase.

Rubin’s figure-ground vase



If we concentrate on the white area of the diagram so that the boundary from whiteto black represents the edge of the object, then we see a white vase against a blackbackground. However, if the edge is visualised the other way, from black to white, thenwe see two faces in silhouette looking at each other in front of a white background. Thisis known ’edge-assignment’ and is critical to shape perception.

The intention of disruptive camouflage is to make this process more difficult. Examplesof camouflage include:

• the British Multi-terrain Pattern on army combat clothing, in which some of thecolours match the surroundings and so break up the edge of the image of thewearer;

• the colour patterns of animals such as the Bengal tiger, which has the same effectagainst a background of tall grasses during the day and the shadows of a forest atnight.



Coherent patterns

In the process of interpreting sensory information, the brain seeks to organise it intocoherent patterns or objects. According to one group of psychologists (Gestalt), thisis achieved by six categories of principles, namely Proximity, Similarity, Closure, GoodContinuation, Common Fate, and Good Form. As a knowledge of these principles is notrequired by the syllabus, only two are given as examples. It should be noted that theseprinciples may not apply if other factors are involved.

Proximity principle

Perception tends to group objects that are close together into a single larger set, andconversely, objects that are far apart into separate sets.

In line (a), the items are evenly spaced and interpreted as a single unit. In line (b), theuneven spacing causes the items to be grouped as three units. In line (c), four groupsare induced by the uneven spacing.

Closure principle

Although the actual shape of the panda is not complete, the brain organises it into asingle shape by filling in the gaps by closure.

Segregation of objects: Questions

Go online

Q1: What is the purpose of disruptive camouflage patterns?

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Q2: How do the principles of Proximity and Closure contribute to perception?

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2.1.2 Perception of distance�

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Learning objective


• state that distance is judged in the field using visual cues such as relative size,superimposition and relative height;

• state that binocular disparity is used to judge distance at close range;

• explain that binocular disparity results from the visual field of the left and righteyes being different, which means seeing objects from a slightly different anglewhere it overlaps;

• state that perceptual constancy means that as objects get closer and the viewingangle changes, they are still perceived to be the same object.

The accurate estimation of distance does not matter to the same extent to all animals.Prey species, for example hare or roe deer, have no problem gauging the distance totheir plant food as it does not run away. Their principal concern is to have as large a fieldof view as possible in order to detect any movement in their surroundings which mightindicate the presence of a predator. Accordingly, their eyes are located on the side ofthe head to maximise their visual field.

To a predatory animal, for example a peregrine falcon swooping at 100mph towards afleeing pigeon, or a lion leaping at the back of a galloping zebra, it is a matter of life ordeath to both the predator and the prey that the former judges the relative position ofthe latter accurately. As predators ourselves, we do not close at potentially lethal speedwith our prey, but the accurate judgment of the distance our arrows or spears had totravel to strike their target, or the distance to a herd of deer or a hungry-looking bear,certainly would have been of critical importance in the past. The eyes of predators aretherefore located on the front of the face. If, on a wilderness safari, you notice a largeanimal contemplating you with a firm, two-eyed stare, it may be thinking about invitingyou to dinner...

In our modern human lives in the West, only recreational hunters and those involved inconservation have to estimate range accurately to ensure a humane kill. Yet we all haveto judge distances, both short and long, in myriad different contexts in every day life, e.g.to climb stairs, cross roads, thread needles or dodge snowballs.

We use a considerable battery of mechanisms to do this, a few of which are capable ofgiving an accurate measurement, and most of which tell us about the relative position ofobjects. The syllabus refers to two of these, namely visual cues and binocular disparity.We also consider perceptual constancy which involves the brain breaking its own rulesabout distance judging.



2.1.2.1 Visual Clues

We use a wide variety of visual clues to judge distance. Here, we consider three ofthem.

Relative size

Objects that possess similar dimensions can appear to have different sizes dependingon their distance from our eyes. This is known as relative size. In the illustration of aroad disappearing towards the horizon, which demonstrates linear perspective, thesmaller telephone poles are interpreted as being further away. In the photograph ofGlen Affric, the pines trees in the foreground, middle ground and in the distance are allof the same height.

Linear perspective

Glen Affric



Superimposition

When objects overlap, those which are partially obscured are perceived to be furtheraway. This is know as superimposition although it is also called interposition.

Relative height in field

In landscape painting and photography, the horizon is often portrayed somewherebetween 1/3 and 2/3 of the way up the image. Objects closest to the horizon appear thefurthest away and those nearest to the top and bottom appear as the closest (relativeheight in field). In the photos of County Mayo and Glen Muick, the vegetation at thebottom of the image appears closest, as do the clouds at the top.

County Mayo and Glen Muick

This makes sense in that, if we look down, the ground on which we are standing is theclosest to us, and if we look straight up, the clouds that we see are (usually) the oneswhich are closest to us.



Perception of distance: Question

Go online

Q3: Explain how visual clues give the impression of depth in the following image.

Jamaica Inn, Bodmin Moor, Cornwall

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2.1.2.2 Binocular disparity

’Binocular disparity’ means that your two eyes do not have the same view of anythingat which you look.

The distance between the pupils of our eyes is typically 60-65mm. Therefore, eacheye views the world from a slightly different position, the effect of which is most markedwith objects close to us. If you hold your right hand up vertically in front of your facewith your thumb touching your nose and shut each eye in turn, you will appreciate thisto maximum effect. Your left eye sees your palm and your right eye sees the back ofyour hand. If you then move your hand slowly away from your face, closing your eyesalternately and comparing each view with what you see with both eyes open, very quicklyyou will discover that with both eyes open you ’see’ only one image, although the viewfrom each eye is noticeably different. Your visual cortex is merging the two-dimensionalimages from each eye into a single, coherent three-dimensional picture. However, thisonly applies around the point of focus of the eyes. If you hold your index fingers in frontof your face about 30cm apart and focus on one of your fingers, the other will appeartwice.



Although with both eyes open we have a total visual field of about 200 ◦, the portion ofthis which is common to both eyes is only about 120◦. As a result of the varying densityof distribution of rods and cones across the retina, over most of this area our visionis not nearly as precise as it is in the centre, in the area on which we are focussed.Consequently, our judgement of distance is also most accurate for objects on which weare focussing.

Binocular disparity is important for judging distance at ranges of up to about 10m;beyond that, the views from each of the eyes are not sufficiently different.

2.1.2.3 Perceptual constancy

We tend to perceive familiar objects as having a standard shape, size, colour and evenlocation, despite wide variations in the conditions under which we are observing them.Thus, you would recognise that the little yellow dog on the other side of the field as aLabrador and your perception would not change as the dog runs over towards you. Infact, as it runs, it changes shape; as it passes under a tree, it changes colour (becauseof the green light filtering through the leaves); and as it gets closer, it forms a muchlarger image. Even if you were looking down on the scene from an upstairs window, witha very different viewing angle, you would not be confused.

The value of perceptual constancy is that it allows us to recognise familiar objects undera wide variety of conditions. This effect is reduced if exposure to the object has beenlimited (e.g. you have never seen a Labrador before) or if the associated clues to itsidentity are reduced (e.g. its colour has changed as a result of ’bog-snorkelling’).

2.1.3 Recognition�

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Learning objective


• state that shape is more important than detail in the recognition of objects;

• explain that we match observed shapes to shape descriptions stored in memoryduring perception;

• explain that inference is used to match incomplete information againstmemorised shape descriptions during perception;

• explain that the perception of a stimulus or object is influenced by a perceptualset of past experience, context and expectation.

Every time we see a familiar object, be it a person, tree, beach, or street, the imagecreated on the retina is different, and yet we discern from that image that the object isnot only similar to one that we have seen before, but actually that it is the same one.This process is complex, involving several different areas of the brain, yet it also takesplace in any animal that is capable of recognition, e.g. an adult butterfly can identify thecorrect food plant for its caterpillar larvae from all of the species growing in a hedgerow.



The role of shape in recognition

Processing of the visual image takes place in a series of increasingly complex stepswhich are located in different areas of the cerebrum. At the simplest level, lines, colourand orientation are distinguished. Boundaries and contours are filled in next, allowingfigure-ground segregation. Finally, all of the information is combined into the finalobject. During this process, no new information is formed, but the existing data is re-organised to emphasise the most detailed information about the object. Overall, it isshape rather than particular detail which is most important in recognition.

Stored memories

The highest level of processing in perception involves identifying an object by matching itwith a stored memory of that object. Once identified, the object can be assigned variousattributes, such as potential uses, whether we like it or not, or whether it constitutes athreat to us. These properties have been linked with this object as a result of our pastexperience of it.

The role of inference

The information provided by our sense organs is often incomplete, but our brain muststill try to make sense of it. This it does by making assumptions, e.g. about whereboundaries are, which leads to drawing conclusions, e.g. about what the rest of apartially concealed object will be.

The influence of perceptual set

Given the extent to which assumptions and inferences are involved in perception,we should not be surprised that the way in which we perceive objects is likely toquite subjective, and dependent on our previous experience, the context in which weencounter the stimulus, and what our expectations are. An obvious example would bethe reaction of opposing sets of supporters to a controversial refereeing decision in afootball match. Depending on past encounters with the other team, the reputations of thereferee and the players, the state of the game, and the position on the pitch, supportersof each side are quite capable of genuinely perceiving the incident in very different ways.



2.2 Memory�

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Learning objective


• state that memory is the process of storage, retention and retrieval ofinformation;

• state that the information stored in memory includes past experiences,knowledge and thoughts;

• explain that all information entering the brain passes first through SensoryMemory and then enters Short-Term Memory;

• explain that information in Short-Term Memory is either passed into Long-TermMemory or is discarded.

In the preceding section about recognition, reference was made to descriptions ofobjects being stored in memory. To be able to confirm that we have seen,smelt orheard something before, we must have been able to convert our initial perception intoa form that can be stored and later retrieved so that we can compare it with our newpercept. By the same token, any animal which can change its behaviour in the light ofexperience, i.e. learn, must also be able to carry out this information storage, retentionand retrieval process. The information which we can store takes all forms; not only areimages, smells, tastes, textures, and sounds stored, but also our feelings about eventsand the details of complex information such as equations or poems. Even our thoughtsare remembered, although these do not pass through the sense organs.

There are different stages in the process of memory. All incoming sensory informationis put into Sensory Memory before some of it is passed almost immediately toShort-Term Memory (STM). As the name implies, information only remains inShort-Term Memory for a brief period and is then either discarded or passed intoLong-Term Memory (LTM).



2.2.1 Sensory Memory�

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Learning objective


• state that Sensory Memory retains all input from the sense organs;

• state that information is retained in Sensory Memory for a few seconds.

Each of our sense organs continuously feeds impulses into the region of the cerebrumwhich relates to that particular sense. Each form of sensory information is processedseparately:

• auditory - echoic memory - processed in the temporal lobe;

• visual - iconic memory - processed in the occipital lobe;

• tactile - haptic memory - processed in the postcentral gyrus of the parietal lobe.

The classic demonstration of visual Sensory Memory (iconic memory) is the drawing ofshapes with a sparkler on a dark night. As the light moves, we briefly ’see’ the shape ofits track through the air.

The information in Sensory Memory is raw data, uninterpreted, and mostly of norelevance to us. Of this vast quantity of information, only a few items pass into Short-Term Memory; the rest is discarded after 1/5 to 1/2 second. Which information is sotransferred is determined by subconscious filtering through the mental process knownas attention. This causes selective concentration on one aspect of the environment tothe exclusion of all others. This is why you shouldn’t speak into a mobile phone whiledriving, or worse, send a text message!

Transfer into Short-Term Memory takes place in the hippocampus, where theinformation from the various sensory areas of the cerebrum is assimilated into a singleexperience.

The position of the hippocampus



Location of Sensory Memory: Question

Go online

Q4: Complete the diagram to show the location of the different types of SensoryMemory.

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2.2.2 Short-Term Memory�

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Learning objective


• state that the memory span of Short-Term Memory (STM) is the number of itemsthat can be stored;

• state that the average memory span for digits is 7 (usual range 5-9);

• state that information may be retained in STM by rehearsal;

• state that information is lost from STM by displacement or decay;

• explain the serial position effect: items at the start of a list are recalled becausethey have been rehearsed and passed to LTM; items at the end of a list arerecalled because they are still in STM; items in the middle of the list are notrecalled as they have been displaced from STM by later items and have notbeen transferred to LTM;

• state that the memory span of STM can be increased by chunking;

• explain that chunking is the grouping of separate items of information so thatthey pass into the memory as a single unit;

• state that Working Memory is an extension of STM;

• state that Working Memory is used to perform cognitive tasks (e.g. reasoning,comprehension).

We often think of Short-Term Memory as information newly-received from the senses,but it may include information recently retrieved from Long-Term Memory or recentmental processing. We can call this extended form of Short-Term Memory ’WorkingMemory’. Short-Term Memory has a limited facility to store information which is knownas the memory span. It makes sense that it is not cluttered with too much information."The Curious Incident of the Dog in the Night-time" by Mark Haddon is an insightfulfictional account of how an autistic boy has difficulty with an excess of information.

Current processing of information, or Short-Term Memory, has a capacity of sevenitems, plus or minus two, for most people. Practice can improve this. For example,’chunking’ items to convert several pieces of information into one can increase thiscapacity greatly. If you were given fifteen random letters to memorise, you could chunkthem in groups of three to make five nonsense words to remember. Phone numbersare often recalled in chunks, the area code as one chunk and the rest put into littlegroups depending on associations.

Short-Term Memory lasts only 15-30 seconds unless rehearsal or repetition is involved.Rehearsal often involves repeating information, such as a telephone number, until it isdialled, although speed-dialling and mobile phone contact lists have reduced thepractice of recalling numbers. Distractions greatly reduce this facility. This repetition isreferred to as acoustic coding and repetition may be aloud or ’in-your-head’.



Given that memories only last for a few seconds normally, and that only around sevenitems are remembered at any one time, Short-Term Memory decays, or is displaced,rapidly.

Serial Position Effect

Storage of memory is greatly enhanced by rehearsal. You may become fed up withyour parents repeatedly recalling the good old days, but this is simply a way to keepmemories alive.

One way to demonstrate memory storage is to investigate the serial position effect.

Serial position effect 1

15 min

Collect at least twenty varied items. Present them briefly, one at a time, in apredetermined sequence, to a friend. Hide them when they are not being shown.

Ask your friend to recall the items, using any descriptions, in any order.

Where did she do best? With the earlier items (the primacy effect) or the last (therecency effect)?

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Even if assuming that someone was paying attention, twenty items are too many to recallfrom Short-Term Memory. The subject initially tries to store the information in Long-TermMemory by rehearsal, using mnemonics, or some other trick, such as associating theitems with a previously learned list.

Most people can only encode seven items in the Short-Term Memory and do not haveenough time to rehearse or repeat all of the items. Thus, the first few items mighthave been stored in the Long-Term Memory and the last few remain in the Short-TermMemory, but storage and, consequently, retrieval of the items mid-list will be haphazard.

Serial position effect 2

10 min

Look at the tables of data and then answer the questions which follow.

Twenty items were shown briefly to a fourth year student. The table below shows whichitems were recalled. For example, the student recalled item 5, but not item 6.

ItemNumber

1 2 3 4 5 6 7 8 9 10

Recalled?√ √ √ √ √ √

ItemNumber

11 12 13 14 15 16 17 18 19 20

Recalled?√ √ √ √ √

Items shown to the student:√

= item recalled



Q5: Using your understanding of the serial position effect, explain the results.

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Q6: What is unusual about the Short-Term Memory of the subject?

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Q7: Sometimes an item is recalled regardless of its position. Why might his occur?

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Working Memory

The concepts of ’Short-Term Memory’ and ’Working Memory’ have been the subject ofmuch research since the development of a classical model of memory in the 1960s.A simple interpretation is that while information is passed into Short-Term Memoryfor storage (for a short period), the manipulation or organisation of this informationis carried out in Working Memory by means of the processes of reasoning andcomprehension.

Short-Term Memory: Questions

Go online

Q8: Complete the sentences by matching the parts on the left with the parts on theright.

Memory span of STM is: STM.

Items remain in STM for: cognitive tasks.

Items are maintained in STM by: displacement and decay.

Items are lost from STM by: 15-30 seconds.

STM memory span can be increased by: 7 (5-9) items.

Working Memory is an extension of: rehearsal.

Working Memory is used to perform: chunking.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q9: When shown a list of twenty items, people can recall a few items from the start ofthe list and a few from the end, but not those in the middle.

i. Explain why the early numbers are recalled.

ii. Explain why the later numbers are recalled.

iii. Explain why the middle numbers are not recalled.

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2.2.3 Long-Term Memory�

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Learning objective


• state that encoding is the process by which information is converted into a formwhich can be passed from STM to LTM;

• state that LTM can store unlimited information indefinitely;

• state that information can be transferred from STM to LTM by rehearsal,organisation or elaboration of meaning;

• state that rehearsal involves repetition of the information to be memorised;

• state that organisation involves grouping the information with other similar items;

• state that elaboration involves linking the information with emotions, images andother memories;

• state that repetition produces shallow encoding of information;

• state that organisation of information into groups with similar propertiesproduces relational encoding of information;

• state that elaboration by linking with previous memories produces elaborativeencoding of information;

• state that relational and elaborative encoding are more permanent than shallowencoding;

• state that retrieval is the recall from LTM to the Working Memory of STM;

• state that retrieval is aided by the use of contextual clues which relate to theconditions under which the memory was formed.

The process of converting information in the form of impulses that enters SensoryMemory into a form which can be stored is known as encoding. Transfer from SensoryMemory to Short-Term Memory is controlled by the mental process of attention overwhich we have no conscious influence.

Transfer from STM to LTM

Transfer from STM to LTM can be achieved by three methods:

1. rehearsal (shallow encoding), which is repeating the information many times -when applied to a list of random words, this repetition is a very inefficient method oftransferring such information to LTM; however, as anyone who plays an instrumentor any sport will know, frequent repetition is essential to the perfection of motorskills, whether it be playing arpeggios in the scale of A minor or escaping frombunkers;



2. organisation (relational encoding) - by grouping an item of information with otheritems of similar type is a form of deep encoding which links the new item withothers already in memory; the creation of mind maps or key-word diagrams ofinformation to be memorised for exams is a prime example of organisation, inwhich individual items are located within a logical framework;

3. elaboration (elaborative encoding) - by linking information to existing memories,or to other information such as emotions, scents, tastes or textures, memories canbe created by another form of deep encoding; thus, if a person’s name can belinked to their interesting choice of shoes/hairstyle/perfume, or the place whereyou met, it is much more likely to be transferred into LTM.

Retrieval

For us to become conscious of items stored in memory, they must be recalled from LTMto STM. This process is greatly aided by information which is linked to the conditions,or context, under which the information was encoded. The reverse of this is also true.You might only have ever seen the person who drives the school bus in that situation sowhen you meet her in the supermarket you find it difficult to place her because some ofthe key contextual clues are missing, e.g. the uniform and the bus. In the same way, thetaste of an ice-cream might remind you of a childhood day by the beach.

Long-Term Memory: Question

Go online10 min


Process by which information is converted to a formwhich can stored in memory:

organisation.

Transfer from STM to LTM by repetition: retrieval.

Transfer from STM to LTM by grouping with similaritems:

rehearsal.

Transfer from STM to LTM by linking with existingmemories:

contextual.

Encoding produced by repetition: elaboration.

Encoding produced by linking with emotions: encoding.

Recall from LTM to STM: elaborative.

Clues which aid recall: shallow.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



2.2.4 Location of memory in the brain�

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Learning objective


• state that LTM can be sub-divided according to the type of information stored;

• state that episodic memory stores events and experiences;

• state that semantic memory stores facts and concepts;

• state that procedural memory stores skills: both motor and cognitive;

• state that emotional memory stores emotional responses to past events;

• state that spatial memory stores information about the location of physicalobjects in space;

• state that the different types of memory are located in different parts of thecerebrum;

• state that episodic and semantic memory are located in the region of thecerebral cortex where the sensory information was first encoded;

• state that procedural memories are linked to long-term changes in the motorcortex;

• state that emotional memories involve links between the cortex and the limbicsystem;

• state that spatial memory is located in the hippocampus of the limbic system.

Location of memory

The information which is stored in Long-Term Memory is located in different parts of thecerebrum depending on the type of information. The types of memory, the informationstored and the location are summarised in the following table.

Type ofmemory Information stored Location in cerebrum

Episodic Events and experiencesArea of cerebral cortex wheresensory information is first encoded

Semantic Facts and conceptsArea of cerebral cortex wheresensory information is first encoded

Procedural Motor and cognitive skills Motor cortex

Emotional Emotional responsesAmygdala of the cortex and thelimbic system

SpatialLocation of a physical objectin space

Hippocampus of the limbic system



Types of memory

The main types of memory are:

• episodic - the memory of events in our lives, including places, times, dates, howwe felt about it, and other people involved;

• semantic - the memory of the meaning of words, facts and concepts, but does notconcern specific events or experiences;

• declarative - episodic and semantic memory together make up one of the twomain types of memory, namely declarative memory. They involve memories, suchas facts and dates, that can be consciously recalled;

• procedural - the memory of how to carry out tasks, both mental and physical. Thiscovers a broad range of complex sets of procedures from putting on your socks tosolving equations and reading. Key points are that these skills can be carried outwithout conscious thought, so do not involve the STM, and that the memories areacquired as a result of frequent repetition.

There are two other forms of memory:

• spatial (or topographic) - the memory of the organisation of our environment andhow we are positioned within it - we store a cognitive map of our world, whichallows us to navigate; this consists of the general layout of places and key locationswithin them;

• emotional - the memory of intense emotional responses, which are usually linkedwith specific events, but may be stored separately - agood example is the feelingof fear; we all know what it feels like to be afraid, but it is very helpful to our survivalthat we should also remember situations which have made us afraid.

Location of memory in the brain: Questions

Go online

Q11: Complete the table with the types of memory from the list.

Type of memory Information stored

Events and experiences

Facts and concepts

Motor and cognitive skills

Emotional responses

Location of physical objects in space

Types of memory: episodic, emotional, procedural, semantic, spatial.



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Events and experiences; Factsand concepts: located in the motor cortex.

Motor and cognitive skills:located in the hippocampus of the limbicsystem.

Emotional responses: area of cerebral cortex where sensoryinformation first encoded.

Location of physical objects inspace:

located in the amygdala of the cortex and thelimbic system.

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2.3 A note about techniques

Early research on human brain function was based on observing the effect of accidentaldamage to particular parts of the brain and the accompanying changes in behaviourand mental abilities. In the mid-20th century, this was amplified by the study oflaboratory animals (particularly rats and monkeys) in which the brain had beendeliberately damaged. Later, this rather coarse approach was superceded by thesurgical implantation of micro-electrodes into the brain which allowed stimulation of veryspecific areas and the observation of the associated behavioural effects.

In the later part of the 20th century, the development of two techniques in particularrevolutionised our understanding of human brain activity:

• magnetic resonance imaging (MRI) - uses powerful electro-magnets to align someatomic nuclei in the body (especially those of hydrogen atoms in water), and thenradio frequency fields to alter the direction of this alignment. The effect is to inducerotating magnetic fields which can be detected by a scanner. In the study of brainactivity, Functional MRI (fMRI) is used to give an indication of changing blood flowto different parts of the brain, and hence relative levels of neural activity. As it usesmagnetic fields and radio signals to detect activity, and not radioactive emissions,MRI carries much less risk than PET;

• positron emission tomography (PET) - this is a form of nuclear imaging whichdetects radiation emitted from biologically active molecules which have beenlabelled with isotopes which typically have a half-life of 15mins or less (so afteran hour, only 6% is left). In the study of brain function, the most frequentlyused molecule is a form of glucose labelled with fluorine-18. Scanners detect theemitted radiation and high levels of emission indicate a high level of respiration,and so an area of the brain which is very active. Because of the risks associatedwith exposure to ionising radiation, PET is mainly restricted to the detection ofcancers. To maximise the acquisition of information, PET scans are now usuallycombined with MRI scans.



2.4 Learning points

Summary

Perception

• Perception is the process by which the brain analyses and makes sense ofincoming sensory information.

• Perception allows us to segregate objects from one another and from theirbackground.

• Perception allows us to judge the distance of objects.

• Perception allows us to recognise objects.

Segregation

• The brain organises sensory information into figures (objects) and grounds(background) during perception.

• In order to make sense of our environment, the brain organises sensorystimuli into coherent patterns during perception.

Perception of distance

• Distance is judged in the field, using visual clues such as relative size,superimposition, and relative height.

• Binocular disparity is used to judge distance at close range.

• Binocular disparity results from the visual field of the left and right eyesbeing different and, where it overlaps, seeing objects from a slightly differentangle.

• Perceptual constancy means that as objects get closer and the viewingangle changes, they are still perceived to be the same object.

Recognition

• Shape is more important than detail in the recognition of objects.

• We match observed shapes to shape descriptions stored in memory duringperception.

• Inference is used to match incomplete information against memorisedshape descriptions during perception.

• The perception of a stimulus or object is influenced by a perceptual set ofpast experience, context and expectation.

Memory

• Memory is the process of storage, retention and retrieval of information.

• The information stored in memory includes past experiences, knowledgeand thoughts.



Summary continued

• All information entering the brain passes first through Sensory Memory andthen enters Short-Term Memory.

• Information in Short-Term Memory is either passed into Long-Term Memoryor is discarded.

Sensory Memory

• Sensory Memory retains all input from the sense organs.

• Information is retained in Sensory Memory for a few seconds.

Short-Term Memory

• The memory span of Short-Term Memory (STM) is the number of items thatcan be stored.

• The average memory span for digits is 7 (usual range 5-9).

• Information may be retained in STM by rehearsal.

• Information is lost from STM by displacement or decay.

• The serial position effect is explained as follows:

◦ items at the start of a list are recalled because they have beenrehearsed and passed to LTM;

◦ items at the end of a list are recalled because they are still in STM;

◦ items in the middle of the list are not recalled as they have beendisplaced from STM by later items and have not been transferred toLTM.

• Memory span of STM can be increased by chunking.

• Chunking is the grouping of separate items of information so they pass intomemory as a single unit.

• Working Memory is an extension of STM.

• Working Memory is used to perform cognitive tasks (e.g. reasoning,comprehension).

Long-Term memory

• Encoding is the process by which information is converted into a form whichcan be passed from STM to LTM.

• LTM can store unlimited information indefinitely.

• Information can be transferred from STM to LTM by rehearsal, organisationor elaboration of meaning.

• Rehearsal involves repetition of the information to be memorised.



Summary continued

• Organisation involves grouping the information with other similar items.

• Elaboration involves linking the information with emotions, images and othermemories.

• Repetition produces shallow encoding of information.

• Organisation of information into groups with similar properties producesrelational encoding of information.

• Elaboration by linking with previous memories produces elaborativeencoding of information.

• Relational and elaborative encoding are more permanent than shallowencoding.

• Retrieval is the recall from LTM to the Working Memory of STM.

• Retrieval is aided by the use of contextual cues which relate to theconditions under which the memory was formed.

Location of memory

• LTM can be sub-divided according to the type of information stored.

• Episodic memory stores events and experiences.

• Semantic memory stores facts and concepts.

• Procedural memory stores skills, both motor and cognitive.

• Emotional memory stores emotional responses to past events.

• Spatial memory stores information about the location of physical objects inspace.

• The different types of memory are located in different parts of the cerebrum.

• Episodic and semantic memory are located in the region of the cerebralcortex where the sensory information was first encoded.

• Procedural memories are linked to long-term changes in the motor cortex.

• Emotional memories involve links between the cortex and the limbic system.

• Spatial memory is located in the hippocampus of the limbic system.





You should have a good understanding of Short-Term Memory before attempting thequestion.


Extended response question: Short-Term Memory

15 min

Give an account of Short-Term Memory under the headings:

A) increasing memory span; (3 marks)

B) serial position effect; (5 marks)

C) transfer from STM to LTM. (2 marks)

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End of Topic 2 test

Go online

Q13: Complete the paragraphs by selecting the correct words from the list, some ofwhich may be used more than once. (14 marks)

In the field, distance is judged by visual �� such as relative ��, ��,and �� height.

Relative �� refers to the apparent �� of similar objects, �� of objectsis used in ��, and �� height refers to �� in the image.

At close range, binocular �� is also used. This uses the fact that each eye has a�� viewpoint.

We perceive familiar objects in the same way despite changing circumstances, such asviewing ��, because of perceptual ��.

Word list : angle, constancy, clues, different, dimensions, disparity, overlap, position,relative, size, superimposition.



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Conversion of information into a form that can be passed into LTM: contextual.

Repetition of information: retrieval.

Grouping of items of information which are similar: shallow.

Linking information with emotions and images:organisationandelaboration.

Type of encoding produced by repetition: rehearsal.

Forms more permanent memories than shallow encoding: encoding.

Recall from LTM to Working Memory: elaboration.

Cues which relate to the conditions under which a memory wasformed:

organisation.

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Memory of events and experiences: procedural.

Memory of facts and concepts: emotional.

Memory of motor and cognitive skills: cerebrum.

Memory of how we felt about past events: sensory regions ofcortex.

Memory of the location of objects:cortex and limbicsystem.

Part of the brain where all memory is located: spatial.

Memories of events and facts are stored: hippocampus.

Skills memories linked to long-term changes: episodic.

Our feelings about past events involve links between them: motor cortex.

Part of the limbic system: semantic.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Enter a word to complete each of the definitions.

Q16: The analysis and interpretation of sensory information is called (1 mark)

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Q17: The brain organises sensory information into objects called (1 mark)

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Q18: The background to these objects is called the (1 mark)

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Q19: The type of patterns of sensory information organised by the brain is (1 mark)

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Q20: The organisation of sensory information into object and background is called (1mark)

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Select the correct words to match the statements.

Q21: Most important in the recognition of objects: (1 mark)

a) colourb) shapec) size

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Q22: Matching descriptions stored in memory: (1 mark)

a) expectationb) perceptionc) recognition

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Q23: Matching incomplete information against descriptions in memory: (1 mark)

a) expectationb) experiencec) inference

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Q24: Not part of a perceptual set: (1 mark)

a) contextb) expectationc) inference

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Q25: What is meant by the term ’memory’? (1 mark)

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Q26: Through which aspect of memory does all information entering the brain firstpass? (1 mark)

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Q27: Which type of memory holds information for a few seconds but retains all visualor auditory input? (1 mark)

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Q28: The number of items held in Working Memory is called the (1 mark)

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Q29: Information is retained in Short-Term Memory by the process of (1 mark)

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Q30: The process by which the storage of new memories causes the loss of othermemories is called (1 mark)

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Q31: Without repetition, information is lost from memory by the process of (1 mark)

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Q32: Short-Term Memory can be improved using the technique of (1 mark)

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Q33: Cognitive tasks involving information in Short-Term Memory are performed by the(1 mark)

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59

Topic 3

Neurons, neurotransmitters andneural pathways

Contents

3.1 Neurons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.1.2 Structure of neurons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613.1.3 Function of the cell body . . . . . . . . . . . . . . . . . . . . . . . . . . . 653.1.4 Function of dendrites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663.1.5 Function of axons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

3.2 Glial cells and myelination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693.2.1 Glial cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693.2.2 Myelination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

3.3 Neurotransmitters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 723.3.1 Chemical transmission at synapses . . . . . . . . . . . . . . . . . . . . 733.3.2 Neurotransmitters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743.3.3 Neurotransmitter threshold . . . . . . . . . . . . . . . . . . . . . . . . . 743.3.4 Removal of neurotransmitters . . . . . . . . . . . . . . . . . . . . . . . . 743.3.5 Excitatory and inhibitory transmitters . . . . . . . . . . . . . . . . . . . . 76

3.4 Neural pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773.4.1 A converging pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793.4.2 A diverging pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793.4.3 A reverberating pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . 793.4.4 Plasticity of response . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

3.5 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833.6 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853.7 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Learning objectives


• describe the structure and function of the cells of the nervous system;

• explain the way in which information is passed on in the nervous system;

• describe the ways in which neurons are linked together in pathways and explainthe effect of such groupings.

60 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS

3.1 Neurons

Nerve tissue comprises neurons, which transmit nerve impulses, and glial cells, whichprovide support for neurons. This first section considers neurons.

3.1.1 Introduction

Any multi-cellular organism requires some method of passing information between cellsto enable coordinated activity to take place.

Cells mainly communicate with one another by means of chemicals, which travelbetween them in a liquid medium. When this involves the secretion of the messengerchemical into a blood stream, this is known as the endocrine system and the chemicalsare hormones. If carried in a double circulation system, such as that of a mammal ora bird, this will deliver the chemical to all parts of the body in a matter of seconds. In ahigher plant, such as an oak tree, things take a little longer. Although efficient, endocrinecommunication is not suited to dealing with a sudden emergency.

All cells have a very small electrical potential difference across the cell membrane.Neurons create a temporary reversal of this potential difference to send a signal alongthe cell (which can be very elongated) at between 1 and 100 m.s-1. The junction betweenneurons is called a synapse, at the centre of which is a gap called the synaptic cleft.By reducing the distance between adjacent neurons to 20-40nm, the diffusion of thechemical carrying the message between cells also takes place very quickly. Neuronsthus provide the fast transfer of information around the body that enables complexanimals to behave in the amazingly diverse and sophisticated ways that we observe.


TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 61

3.1.2 Structure of neurons�

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Learning objective


• describe that the nervous system consists of a range of different cells calledneurons;

• explain that neurons are grouped together to form the brain and spinal cord ofthe central nervous system (CNS), and the nerves of the peripheral nervoussystem;

• state that neurons receive and transmit impulses (a form of electrical signal);

• state that there are three main types of neuron: sensory neurons, motorneurons and interneurons;

• state that sensory neurons carry impulses into the CNS from sense organs;

• state that motor neurons carry impulses out from the CNS to effectors such asmuscles and glands;

• state that interneurons are found in the CNS where they connect with otherneurons;

• describe a neuron as consisting of a cell body with protruding fibres in the formof one axon and many dendrites.

Neurons are the specialised cells which carry nervous impulses around the body,allowing the senses to communicate with the brain and the brain to coordinateresponses. The human nervous system (NS) comprises some 1012 of these cells whichare typically only a few micrometres in diameter.

There are many different types of neuron, of which we study three here:

• sensory neurons, which carry impulses into the Central Nervous System (CNS)from sense organs;

• motor neurons, which carry impulses out from the CNS to effectors such asmuscles and glands;

• interneurons (also called relay or association neurons), which exist in many formsand are found in the CNS where they connect with other neurons.

These neurons are grouped together to form the brain and spinal cord of the CNS, andthe nerves of the Peripheral Nervous System.

Each neuron consists of a cell body, much like the typical animal cell in structure, withan axon extending from the cytoplasm. These can be up to a metre long in humansalthough they are often much shorter; in the CNS they are very short. The axon iswrapped in a sheath of lipoprotein called myelin. Impulses begin in the dendrites,which are projections from the axon in sensory neurons, and from the cell body of motorneurons. The impulses then travel towards the cell body and on to the axon terminals atthe end of the axon.



The cell bodies of sensory neurons are located within the vertebrae, which surroundand protect the spinal cord. In motor neurons the cell body lies within the central greymatter of the spinal cord, surrounded by the outer white matter, which is composed ofaxons with their fatty myelin sheaths. The grey matter of the brain similarly consistsmainly of cell bodies and dendrites, whilst the white matter consists of axons.

The diagram shows how these cells are organised in a simple reflex.

A simple reflex

Neurons themselves are specialised according to function. To achieve this, they requireslight adaptations in structure.

Look at the different structures of sensory, motor and inter-neurons.

Sensory neurons are adapted to take messages from sensory receptors in the skinand the specialised sense organs (the nose, tongue and ears) to the brain.

Sensory neuron

Note that the cell body sits part way along the axon and that there are no dendrites onthe cell body.



Motor neurons have many dendrites protruding from the cell body, which is end-on tothe axon.

Motor neuron

If a motor neuron that links the spinal cord with the foot was enlarged until the cellbody was the size of a tennis ball, its dendrites would fill your living room and the axonwould be 1.6km long, yet only 13mm in diameter. Axons vary between 0.2 and 300μm(1 micrometre ≡ 1μm ≡ 1 x 10-6 m) in length. A human axon is typically 50μm indiameter, excluding the myelin sheath. In a large mammal, a single motor neuron thatlinks the spinal cord with a digit might be 2 metres long, though the synapses betweenone neuron and its neighbour are around 200 x 10 -9 metres in size.

Interneurons typically have a large number of dendrites and a very short axon, althoughthey have a wide variety of different structures based on this basic pattern.

Interneuron

Note that the axon is very short and lacks myelination.



Structure of neurons: Question

Go online15 min

Q1: Complete the diagram using the labels provided.

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3.1.3 Function of the cell body�

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Learning objective


• explain that the cell body contains the nucleus with its DNA which controls theactivity of the cell.

A neuron is a specialised cell, but it starts life as a normal animal cell. A generalisedanimal/plant cell is shown below. Make sure you can label and describe all the parts ofan animal cell, espeically the nucleus, cytoplasm, ribosomes and mitochondria.

A generalised cell

Neurons, like muscle cells, develop long extensions to help them fulfil their functions. Asingle neuron may be a metre long in a human.



Cell bodies

The cell body contains a nucleus and cytoplasm like a normal cell. It has manyribosomes that make the proteins which act as neurotransmitters at the gaps, orsynapses, between one neuron and the next. These tiny gaps act like switches andmay allow or prevent signals passing from one neuron to the next. The messengerswhich ’jump’ between the gaps and pass the signals are called neurotransmitters. Thereare also many mitochondria that provide the energy for active transport, which helpsmaintain electrical potential and reabsorb neurotransmitters.

The nucleus controls the activity of the cell and carries the DNA coding for the formationof all proteins in the cell, including those required in the axon terminals which may beup to a metre distant from the cell body. There is, therefore, a rapid transport system ofmicrotubules to convey the proteins vital to the functioning the axon terminals.

3.1.4 Function of dendrites�

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Learning objective


• state that dendrites are stimulated by sense organs or other neurons to carryimpulses towards the cell body.

The diagram below shows the general structure of a neuron. The dendrites areprojections from the cell body or, in some sensory neurons, from the forward extensionof the axon (sometimes called the dendron). Their function is to form synapses with theaxon terminals of other neurons or with cells in sense organs, and to convey impulsestowards the cell body.

General neuron structure showing dendrites



3.1.5 Function of axons�

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Learning objective


• state that the axon ends in many divisions called axon terminals;

• state that the axon carries impulses in one direction from the dendrites to theaxon terminals;

• explain that myelin surrounds the axons, greatly increasing the speed ofconduction of impulses along the nerve fibres as impulses jump from node tonode in the myelin sheath.

Each neuron has only a single axon, which ultimately divides to form several axonterminals. The axon carries the impulse away from the cell body towards the axonterminals, which form synapses with the dendrites of the next neurons on the neuralpathway or with effectors such as glands and muscles (neuromuscular junctions).

General neuron structure showing the axon with its myelin sheath

Axons are bundled together to form the nerves that we commonly speak of.



Nerve bundle with many axons

Electrical impulses transmit signals along these axons. Neurotransmitters take theinformation from the dendrite of one cell across the synapse, or gap, to the dendrite ofthe next axon. The axons must not leak out signals otherwise confusion would arise assignals jump from the axon terminal of one neuron to the dendrite of the next neuron.Additionally, if the signals leaked out, they would become weaker and weaker as theytravelled along the axons; this occurs in people who suffer from illnesses such as MS.Consequently, they are insulated by layers of myelin sheath, which wraps around theaxon like a Swiss roll.

Neurons: Question

Go online


Neurons: cell body, axon and dendrites.

Neurons receive and transmit: dendrites.

Neurons comprise: neuromuscular.

DNA in the cell body codes for: type of nerve cell.

Carry impulses towards the cellbody:

synaptic cleft.

Axon terminals and dendrites form: impulses.

The gap between an axon terminaland a dendrite:

all cell proteins.

Junction between an axon and amuscle fibre:

synapses.

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3.2 Glial cells and myelination�

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Learning objective


• state that glial cells support and maintain neurons by:

◦ producing the myelin sheath;

◦ acting homeostatically to maintain a constant environment around theneuron;

◦ removing debris by phagocytosis.

• state that myelination begins in the foetus and continues into adolescence;

• explain that incomplete myelination causes an infant’s response to stimuli to beslower and less co-ordinated than that of older children or adults;

• explain that certain diseases cause a loss of co-ordination by destroying themyelin sheath, e.g. multiple sclerosis.

This section considers glial cells, the other important type of cell in nerve tissues.

3.2.1 Glial cells

Although they are not neurons, glial cells (also known as neuroglia) are an essential partof the nervous system. Just as white blood cells are a diverse group of cells, neurogliaare also a class of cells, each form of which carries out a different function.

One type is found in the central nervous system. If damage occurs to the neurons,they multiply and remove debris by phagocytosis. Others constantly sample andhomeostatically regulate the chemical environment of the neurons, removing excessions and recycling neurotransmitters so that the neuron functions in very constantconditions.

They are also a key element in the blood-brain barrier, which ensures that only smallmolecules, such as O2, CO2, and hormones can pass freely between the blood and thecerebrospinal fluid which bathes the brain. All other molecules, e.g. glucose, must beactively transported if they are to enter the brain.

Other types of glial cells, including Schwann cells, are responsible for myelination.These cells closely surround and give physical support to the axon.

Although the term ’nerve cell’ is often used when referring to neurons, glial cells are alsoimportant nerve cells and so an effort should be made to always use the correct termfor the neuron.



Glial cells: Question

Go online15 min

Q3: Complete the paragraph about glial cells by using words from the list below.

The nervous system contains more than neurons. About 15% of the cells in thecerebrum are �� cells which support and maintain the neurons in several ways.Some of them monitor the conditions surrounding the neurons and maintain a constantenvironment by ��. Others help repair damage by removing cell debris by��.

Another cell of this type, called the Schwann cell, wraps lipoprotein membrane aroundaxons forming the �� sheath, the effect of which is to greatly �� theconduction of impulses. Starting well before birth, this process, known as ��,continues until ��. This explains why an infant’s responses to stimuli are less�� than an adult’s.

Word list : accelerate, adolescence, coordinated, glial, homeostasis, myelination, myelin,phagocytosis.

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3.2.2 Myelination

The myelin is pinched into sausage-shaped pieces at short intervals. The constrictionsare called nodes (nodes of Ranvier). These have a very important function becausethey speed up nervous transmission by a factor of 50. Rather than electrical impulsestravelling along axons at 2 metres per second, they move along much faster, jumpingfrom node to node. The myelin sheath stops sodium and potassium ions from crossingthe membrane so the impulse ’rushes’ along to the tiny gap in the myelin where ionexchange can occur. A myelinated fibre of diameter 18μm and with nodes at 1.5mmapart will conduct at 100m/s. The larger the diameter, the faster the impulse travels.

Neurons fire on an ’all-or-nothing’ basis. If an impulse arriving causes enough of aneffect at the next neuron, it will ’fire’. If the impulse is weak, the next neuron in thecircuit will not fire. However, if a very strong signal arrives, it will not make the signalpassing to the next neuron any larger. The signals from several neurons which havetheir synapses together at any adjacent neuron may have summative or, on the otherhand, competitive ’inhibitory’ effects. It is repeated firing due to successive signals whichcauses a stronger effect, such as a tighter flexing of a muscle. When the impulse leaksout due to lack of complete myelination, as in MS, repeated firing cannot occur and fullcontraction becomes impossible, leading to a weak grip for example.

It is interesting to note that it was this ’all-or-nothing’ status of the nervous system,discovered by biologists a century ago, which led to the development of the binaryrevolution called computing.

Slides and micrographs of neurons

15 min

To examine slides and micrographs of neurons, use a computer to perform a Googleimage search for "micrograph neurone".

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Myelination

Myelination begins during the fourth month of pregnancy and continues intoadolescence. As a result, a newly born infant has an immature nervous system. Thisexplains the initial lack of coordination of responses. The ’bones’ of the skull areincompletely closed, leaving a gap called the fontanelle to allow the brain to continueto grow for several months after birth. The skeleton is initially made of cartilage. Theflexibility of cartilage, and the mobile nature of the separate ’bones’ of the skull, alloweasy passage down the birth canal. Crucially, continued growth of the nervous system,particularly of the brain, is accommodated. The fontanelle closes between the ages of18 months and two years. (Recent research has shown that further re-organisation ofthe brain seems to occur in the late teens, especially in boys. This explains why we feelso clumsy for a wee while, then!)

Infancy

Myelination of axons proceeds rapidly during the months after birth. This process isessential. The axons wrap themselves around lipoprotein derived from cell membranes.Lack of myelin can have severe consequences. In Muscular Sclerosis (MS), thereis patchy loss of myelin and this leads to delayed or blocked conduction of nervousimpulses.

There are some unmyelinated peripheral neurons that are only encased in cytoplasmand these are less insulated from leakage of electrical conduction. In addition tocarrying impulses less securely, they are 50 times slower at carrying impulses becauseof this lack of insulation. Although impulses do not travel as fast as electricity, or lightand sound waves, they can still achieve speeds of up to 100 metres per second. Thespeed of transmission increases with temperature, giving so-called ’warm-blooded’animals a great advantage over their cold-blooded competitors.

Nerve Transmission

Myelination leads to small nodes forming along an axon. Each node is around 1μm indiameter and approximately 1mm from its neighbour.

Electrical impulses are carried along axons because the membrane becomesdepolarised and repolarised by active exchange of ions. Depolarisation can ’jump’ fromone node to the next in myelinated neurons, whereas it can only flow smoothly andslowly along unmyelinated neurons.

As new nervous tissue grows, the number of synapses formed between adjacentneurons multiplies exponentially. It is this massive increase in number of synapses andthe ability to repeatedly fire neurotransmitters across them by means of rehearsal orrepetition that leads to the impressive memory feats and communication skills ofhumans.

Myelination: Question

Go online

Q4: A myelinated fibre, 18μm in diameter, carries an impulse at 100m/s. Assumingthat an impulse goes a quarter as fast through a fibre (axon) half as wide, how manyseconds does it take for an impulse to travel 2m through an axon of diameter 9μm?

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3.3 Neurotransmitters�

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Learning objective


• state that neurotransmitters are chemicals which relay signals from neuron toneuron in the central and peripheral nervous systems;

• state that neurotransmitters also transmit signals between neurons and othertarget cells e.g. muscle fibres, endocrine glands;

• state that neurotransmitters are secreted into the gap (the synaptic cleft)between the neuron and the next cell;

• state that neurotransmitters are stored in vesicles;

• state that the arrival of an impulse causes the release of the neurotransmitters;

• state that neurotransmitters diffuse across the synaptic cleft and bind toreceptors on dendrites;

• state that, if sufficient neurotransmitters attach to the receptors, a threshold isreached and an impulse is triggered;

• state that signals may be excitatory or inhibitory, depending only on the receptoron the receiving dendrite and not on the type of neurotransmitter;

• explain that neurotransmitters must be immediately removed to preventcontinuous stimulation of the post-synaptic neurons;

• state that there is a wide range of different chemicals which act asneurotransmitters, e.g. noradrenalin and acetylcholine;

• state that neurotransmitters are either removed by enzyme action (e.g.acetylcholine) or by re-uptake (e.g. noradrenalin);

• explain that synapses can filter out weak impulses arising from insufficientsecretion of a neurotransmitter;

• explain that, by summation, a series of weak stimuli can combine to reach thefiring threshold in the post-synaptic neuron.

Neurotransmitters comprise a wide range of chemicals (often amino acids or relatedcompounds) which transfer the ’message’ of the impulse across the gap betweenneurons at the synapse or from a neuron to an effector organ such as an endocrinegland or a muscle.

A synapse between a motor neuron and a muscle cell is called a neuromuscular junction.



Neuromuscular junction

Synapses: chemical transmission by neurotransmitters

It is easy to think of synapses simply as gaps between neurons. We cannot have eachmuscle and sense organ supplied by its own single neuron from the brain so gaps areinevitable. Synapses, however, are not merely junctions. They act as filters and mustcope with rapid and repeated firing of neurons. How do they manage this?

3.3.1 Chemical transmission at synapses

Each neuron might be connected to hundreds of other neurons. The dendritesalmost touch. There are thousands of possible permutations of interconnections, eachseparated only by a tiny gap. Chemicals called neurotransmitters are secreted at eachsynapse. They cross the gap to the post-synaptic dendrite. Will they excite it enoughto fire? Will they inhibit it, effectively switching it off? It all depends on where theneurotransmitter arrives.

Synapse anatomy



3.3.2 Neurotransmitters

Chemical messengers, called neurotransmitters, travel across the synaptic cleft tocommunicate impulses to the next neuron. The neurotransmitters acetylcholine andnoradrenaline are contained in vesicles in dendrites until they are needed. Thisensures that resources are not wasted and that chemicals are not promoting unwantedreactions indiscriminately. An impulse arriving at a synaptic terminal stimulates thesynaptic vesicles to secrete their contents by exocytosis into the synaptic cleft. Theseneurotransmitters are recognised by receptors on the post-synaptic dendrite.

Neurotransmitters: Questions

Go onlineQ5: Give two reasons why neurotransmitters are contained in vesicles.

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Q6: Why are mitochondria and ribosomes found in large numbers in the pre-synapticdendrites?

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3.3.3 Neurotransmitter threshold

Neurotransmitters work on the basis that the neuron will ’fire’ if a certain threshold isreached. Each neurotransmitter binds to a specific receptor molecule on the adjacentneuron in a way similar to the lock and key mechanism of enzymes. It is the receptorwhich determines whether signals are stimulatory or inhibitory. A tiny quantity ofneurotransmitter has no effect, but a very large quantity has no extra effect. Thus weaksignals are filtered out, but strong signals do not paralyse the nervous system withexcessive contractions. We should remember that each neuron may receive thousandsof synapses from a network of incoming neurons.

As a result, a series of weak stimuli can combine to reach the firing threshold in thepost-synaptic neuron, a process known as summation.

3.3.4 Removal of neurotransmitters

When acetylcholine is released at the synaptic cleft, it binds to the receptors on thedendrites of the receiving neuron. If the number of excitatory signals exceeds thenumber of inhibitory signals, the neuron will ’fire’, carrying an impulse to the nextsynapse, but this only occurs if a certain threshold is reached. To avoid repeatedcontractions from the same stimulus, acetylcholine is immediately destroyed by anenzyme called acetylcholinesterase. This process is called degradation. This enzymewas first discovered in an unfortunate individual who had no acetylcholinesterase owingto a genetic mutation. The breakdown products are reabsorbed by active transport (seebelow) using energy from the adjacent mitochondria.

Noradrenaline also needs to be removed, but is not degraded. It is reabsorbed backinto the synaptic ending whence it came. This process is called re-uptake.



Diffusion and active transport: Comparison

Go online

This activity illustrates the difference between diffusion (a process driven solely bydifferences in concentration) and active transport (which uses energy from ATP to movematerials across membranes, even against the concentration gradient).

Diffusion across a membrane is a passive process. The net movement of moleculesacross a membrane will stop when the concentration of molecules is the same on bothsides of the membrane, although movement continues.

Diffusion across a membrane

Active transport across a membrane is a process that uses energy. This means that aconcentration gradient can build up across the membrane, which would not be possiblewith diffusion.

Active transport across a membrane

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3.3.5 Excitatory and inhibitory transmitters

Noradrenaline and acetylcholine do not by themselves have opposite effects. They acton different receptor structures, which then mediate their effects on the organs of thebody. It is the receptors in the receiving neuron which are primed to have oppositeeffects. Think of yourself as a neurotransmitter acting on light switches in a room. Yourpresence can move a switch up or down (neurotransmitter-receptor binding), but whichlight goes on, or off, (the effect of the transmitter) depends on how the switch is wired tothe lights.

Acetylcholine from a parasympathetic neuron in the heart will inhibit heart rate andvolume. However, acetylcholine in the alimentary canal promotes peristalsis.

Some acetylcholine receptors also respond to nicotine from cigarettes, often leading totobacco addiction in those who smoke. They can also be blocked temporarily byanaesthetics called muscle blockers (relaxants).



3.4 Neural pathways�

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Learning objective


• state that a converging pathway is where several neurons pass messages on toa single neuron;

• state that a converging pathway increases the sensitivity to both excitatory andinhibitory signals;

• state that rods in the retina are an example of a converging pathway;

• state that a diverging pathway is where a single neuron passes messages on toseveral neurons;

• state that a diverging pathway influences several neurons or tissues at the sametime;

• state that fine motor control in the fingers is an example of a diverging pathway;

• state that a reverberating pathway is where neurons later in the pathwaysynapse with earlier ones, sending the impulse back through the circuit;

• state that the wake-sleep cycle is an example of a reverberating pathway;

• state that new neural pathways can be developed to:

◦ create new responses;

◦ bypass areas of brain damage;

◦ suppress reflexes;

◦ suppress responses to sensory impulses.

• state that the development of new neural pathways creates a plasticity ofresponse.

The multiplicity of neuron connections confers further advantages. In some cases,converging pathways increase the strength of a signal, whilst in others, divergingpathways allow a signal from a specific area to be distributed to a group of neurons. Inreverberating pathways, positive feedback causes continuous stimulation of the neurons.



Neural pathways: Comparison

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Convergent pathway

Divergent pathway

Reverberating pathway

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3.4.1 A converging pathway

In the retina of the human eye, there are cone-shaped neurons which can only be firedby a high intensity of light. They respond to colour and only fire in bright light. Theirneural pathways show little convergence. Each neuron synapses with one other neuronas it takes the message to the brain. However, rod-shaped neurons take up most ofthe retina. They are fired by dim light. Thus each has a weak impulse. However, manyrods converge to synapse with a single neuron. Summation at the synapses causes theseveral weak stimuli to fire the neuron, allowing rods to give us a monochrome view indim light.

Notice in the diagram below that the incoming light has to pass through the layer ofnerve tissue before reaching the photoreceptor cells. This is an example of ’not-very-intelligent’ design!

Retina of an eye showing rods and cones

3.4.2 A diverging pathway

Fine motor control of the hand is brought about by a single impulse from a neuron in themotor area of the brain. The neuron synapses with a group of neurons which carry thesignal on, eventually causing contraction in the groups of skeletal muscles that controlthe hand and fingers.

3.4.3 A reverberating pathway

In some neural pathways, branches of some axons extend backwards towards thesource of the impulse, causing the earlier neurons in the pathway to be continuouslystimulated. As a result, once stimulated, the pathway continues to stimulate itself.

Such pathways are found in the brain-controlling rhythmic activities, such as breathingand the sleep-wake cycle, muscular coordination and consciousness.



3.4.4 Plasticity of response

After an injury such as a stroke, the brain can adapt, especially if therapy is quicklyavailable. The function of a damaged part may be taken over by another, demonstratingplasticity (adaptability) of function. This is referred to as major plasticity. Minor plasticityrefers to occasions when portions of the brain can be temporarily ’shut down’. Examplesof the latter include suppressing a reflex sneeze or when workers in a distillery ’ignore’the smell of the mash after a while.

This plasticity of response is created by the development of new neural pathways. As aresult, the brain can bypass damaged areas, create new responses, and suppress bothreflexes and the response to sensory stimuli.

Suppressing brain reflexes

5 min

Carry out an investigation into the ability of the brain to suppress reflexes or sensoryimpulses.

For example, gently release the air from a balloon into your eye and see if you cansuppress reflex blinking.

Background information is given below, in case you would like to know how a reflexworks, though this is not necessary for the exam.

Background information

It is interesting to note that special relay neurons exist in the spinal cord to allow short-circuiting of normal response times in occasions of danger. Relay neurons short-circuitthe normal pathway to the brain. The message will continue to travel to the brain, thougha response will already have occurred, avoiding danger. In your experiment, you shouldshow that plasticity of response can allow you to over-ride the reflex response.

The classic reflex response is obtained by tapping the flexed knee which will kick outinvoluntarily.



Reflex action in a knee

This apparently artificial reflex is in fact one which helps us regain balance, straighteningour legs (and arms) after a trip or slip has caused our legs to bend at the knee. Thisstimulates the stretch receptors in the quadriceps and triggers the reflex.

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Neural pathways: Questions

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Q7: Pathway where several neurons pass messages to one:

a) convergingb) divergingc) reverberating

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Q8: Pathway where a single neuron passes messages on to several:


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Q9: Pathway where messages are passed back to earlier neurons:


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Q10: Pathway involving rods in the retinas:


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Q11: Pathway giving fine motor control in the fingers:


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Q12: Pathway controlling the wake-sleep cycle:


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Q13: New neural pathways create:

a) brain damageb) plasticity

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Q14: New neural pathways bypass:

a) brain damageb) plasticity

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3.5 Learning points

Summary

Neurons

• The nervous system comprises a range of different cells called neurons.

• Neurons are grouped together to form the brain and spinal cord of thecentral nervous system, and the nerves of the peripheral nervous system.

• Neurons receive and transmit impulses (a form of electrical signal).

• There are three main types of neuron: sensory neurons, motor neurons andinterneurons.

• Sensory neurons carry impulses into the Central Nervous System (CNS)from sense organs.

• Motor neurons carry impulses out from the CNS to effectors such asmuscles and glands.

• Interneurons are found in the CNS where they connect with other neurons.

• A neuron consists of a cell body with protruding fibres, in the form of oneaxon and many dendrites.

• The cell body contains the nucleus with its DNA, which controls the activityof the cell.

• Dendrites are stimulated by sense organs or other neurons to carryimpulses towards the cell body.

• The axon ends in many divisions called axon terminals.

• The axon carries impulses in one direction from the dendrites to the axonterminals.

• Myelin surrounds the axons, greatly increasing the speed of conduction ofimpulses along the nerve fibres as impulses jump from node to node in themyelin sheath.

Glial Cells and Myelination

• Glial cells support and maintain neurons by:

◦ producing the myelin sheath;◦ acting homeostatically to maintain a constant environment around the

neuron;◦ removing debris by phagocytosis.

• Myelination begins in the foetus and continues into adolescence.

• Incomplete myelination causes an infant’s response to stimuli to be slowerand less co-ordinated than that of older children or adults.



Summary continued

• Certain diseases cause a loss of co-ordination by destroying the myelinsheath, e.g. multiple sclerosis.

Neurotransmitters

• Neurotransmitters are chemicals which relay signals from neuron to neuronin the central and peripheral nervous systems.

• Neurotransmitters also transmit signals between neurons and other targetcells, e.g. muscle fibres, endocrine glands.

• The junction between neurons is called a synapse.

• The gap between one neuron and the next is called the synaptic cleft.

• The junction between neurons and muscle cells is called a neuromuscularjunction.

• Neurotransmitters are secreted into the gap, the synaptic cleft, between theneuron and the next cell.

• Neurotransmitters are stored in vesicles.

• The arrival of an impulse causes the release of the neurotransmitters.

• Neurotransmitters diffuse across the synaptic cleft and bind to receptors ondendrites.

• If sufficient neurotransmitters attach to the receptors, a threshold is reachedand an impulse is triggered.

• Signals may be excitatory or inhibitory, depending only on the receptor onthe receiving dendrite and not on the type of neurotransmitter.

• Neurotransmitters must be immediately removed to prevent continuousstimulation of the post-synaptic neurons.

• There is a wide range of different chemicals which act as neurotransmitters,e.g. noradrenalin and acetylcholine.

• Neurotransmitters are either removed by the action of an enzyme (e.g.acetylcholine) or by re-uptake (e.g. noradrenalin).

• Synapses can filter out weak impulses arising from insufficient secretion ofneurotransmitter.

• By summation, a series of weak stimuli can combine to reach the firingthreshold in the post-synaptic neuron.

Neural Pathways

• A converging pathway is where several neurons pass messages on to asingle neuron.



Summary continued

• A converging pathway increases the sensitivity to both excitatory orinhibitory signals.

• Rods in the retina are an example of a converging pathway.

• A diverging pathway is where a single neuron passes messages on toseveral neurons.

• A diverging pathway influences several neurons or tissues at the same time.

• Fine motor control in the fingers is an example of diverging pathways.

• A reverberating pathway is where neurons later in the pathway synapse withearlier ones, sending the impulse back through the circuit.

• The wake-sleep cycle is an example of a reverberating pathway.

• New neural pathways can be developed to:

◦ create new responses;

◦ bypass areas of brain damage;

◦ suppress reflexes;

◦ suppress responses to sensory impulses.

• The development of new neural pathways creates a plasticity of response.



You should have a good understanding of sensory and motor neurons before attemptingthe question.


Extended response question: Sensory and motor neurons

15 min

Compare and contrast sensory and motor neurons and describe events that occur at asynapse. (10 marks)

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End of Topic 3 test

Go online


Cells that make up the nervous system: myelin.

Transmitted through the nervous system: dendrites.

Neurons that carry information into the CNS: motor neurons.

Neurons that connect neurons: multiple sclerosis.

Neurons that connect the CNS to glands: glial.

Carry impulses towards the cell body: axon terminals.

Found at the end of the axon: sensory.

Increases speed of conduction of impulses: interneurons.

Cells which produce the myelin sheath: neurons.

Results from destruction of the myelin sheath: impulses.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q16: Complete the paragraphs by selecting words from the list. (15 marks)

Neurotransmitters are chemicals which relay signals between �� in the CNS andbetween neurons and ��. The junction between neurons is called a ��

and that between neurons and muscle fibres is a �� junction. Neurotransmittersare secreted by �� into synaptic cleft, and �� across the gap and bindto receptors on the �� of the next neuron.

Signals may be excitatory or ��, depending only on the �� on thereceiving dendrite and not on the type of neurotransmitter. Neurotransmitters must beimmediately removed to prevent continuous �� of the post-synaptic neurons.Neurotransmitters are either removed by �� action (e.g. acetylcholine) or byre-uptake (e.g. ��).

Synapses can filter out weak impulses arising from �� secretion ofneurotransmitter.

If sufficient neurotransmitters attach to the receptors, a �� is reached and animpulse is triggered. By �� a series of weak stimuli can combine to reach thefiring threshold in the post-synaptic neuron.

Word list : dendrites, diffuse, enzyme, exocytosis, glands, inhibitory, insufficient,neuromuscular, neurons, noradrenalin, receptor, stimulation, summation, synapse,threshold.



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Several neurons pass messages on to a single neuron:reverberatingpathway.

An example of a converging pathway: fine motor control.

Increased by a converging pathway: converging pathway.

A single neuron passes messages on to several neurons: wake-sleep cycle.

An example of a diverging pathway:new neuralpathways.

Neurons later in the pathway synapse with earlier ones:plasticity ofresponse.

An example of a reverberating pathway: rods in the retina.

New responses are created by their development: sensitivity to signals.

Result of the development of new neural pathways: diverging pathway.



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The following diagram represents a neuron in the central nervous system.

Q18: Identify the structures labelled A. (1 mark)

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Q19: Identify the structure labelled B. (1 mark)

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Q20: Identify the structures labelled C. (1 mark)

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Q21: Where is myelin found on a neuron and what is its function? (2 marks)

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Q22: Which type of neuron conducts impulses between the CNS and effector organs?(1 mark)

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Q23: Interneurons conduct impulses between what? (1 mark)

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Q24: Which type of neuron conducts impulses between sense organs and the CNS? (1mark)

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Q25: What is the gap between neurons called? (1 mark)

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Q26: What joins a neuron to a muscle fibre? (1 mark)

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Q27: List three functions of glial cells. (3 marks)

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Q28: Name a disease that destroys the myelin sheath and describe its effect. (2 marks)

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Q29: Where are neurotransmitters stored? (1 mark)

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Q30: What causes the release of neurotransmitters? (1 mark)

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Q31: How do neurotransmitters cross between neurons? (1 mark)

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Q32: What do neurotransmitters bind to? (1 mark)

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Q33: Explain the process of summation. (2 marks)

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Q34: What type of pathway involves several neurons passing messages to one neuron?(1 mark)

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Q35: Give an example of the above type of pathway. (1 mark)

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Q36: Describe the neuron connections of a diverging pathway, an example of which isthe fine motor control of the fingers. (1 mark)

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Q37: What type of pathway has neurons later in the pathway that synapse with earlierones? (1 mark)

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Q38: Give an example of the above type of pathway. (1 mark)

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Q39: What is created by the development of new neural pathways? (1 mark)

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Q40: State two results of the development of new neural pathways. (2 marks)

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91

Topic 4

Neurotransmitters, mood andbehaviour

Contents

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

4.2 Dopamine and the reward pathway . . . . . . . . . . . . . . . . . . . . . . . . 93

4.3 Endorphins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

4.4 Neurotransmitter-related disorders and their treatment . . . . . . . . . . . . . 95

4.4.1 Drugs used to treat neurotransmitter-related disorders . . . . . . . . . . 96

4.4.2 Neurotransmitter-related disorders and their treatment . . . . . . . . . . 96

4.5 Mode of action of recreational drugs . . . . . . . . . . . . . . . . . . . . . . . 100

4.5.1 Modes of action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

4.6 Drug addiction, sensitisation and tolerance . . . . . . . . . . . . . . . . . . . . 103

4.7 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105


4.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Learning objectives


• describe the role of dopamine in the reward pathway of the brain;

• describe the role of endorphins in the body and the factors which increase theirproduction;

• explain how neurotransmitter-related disorders are treated;

• explain the mode of action of recreational drugs;

• explain the causes of drug addiction and tolerance.

92 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR

4.1 Introduction

Certain neurotransmitters are particularly associated with the control of mood andbehaviour. Mood is a psychological state which is less immediately affected by eventsthan emotion, and less permanent than personality or temperament. Behaviour is theresponse of an organism to internal and external stimuli.

In particular, we will consider the role of the neurotransmitters dopamine andendorphins. While these are both produced and exert an effect outside, as well asinside, the brain, we will restrict our study to their actions in the brain as this is wheremood and behaviour are determined. Within the brain, they act not only in the cerebrum,but also in those areas of the mid-brain located in the vicinity of the hypothalamus.

Dopamine causes feelings of pleasure and euphoria, and, consequently, any activitywhich induces dopamine release will tend to be repeated. It is therefore associated withbeneficial behaviours, such as eating when hungry. This reward pathway is also usedin training and teaching. The action of dopamine, particularly in relation to the rewardpathway, is central to many of the other subjects in this topic.

Endorphins are a group of at least twenty related chemicals which are produced from thepituitary and the hypothalamus in response to a variety of different stimuli, both physicaland mental. They act like the opiate drugs after which they are named, relieving painand creating a feeling of well-being. This effect is achieved because the increased levelsof endorphins in turn stimulate the release of dopamine.

A wide range of medical conditions are linked to neurotransmitters, associated both withtheir under- and over-production. Treatment of these disorders can be complicated bythe inability of the neurotransmitters involved to cross the blood-brain barrier.

An immense variety of chemicals can affect or imitate the action of neurotransmitters,especially in the reward pathway. Where these are consumed voluntarily because of themood they induce, they are referred to as recreational drugs. Some are administeredmedicinally as analgesics to control pain, e.g. morphine, an opioid derived fromthe Opium Poppy (Papaver somniferum). Exposure to such chemicals, especially ifregularly repeated or prolonged, leads to addiction and/or to tolerance. Addiction maybe in the form of a physiological or a psychological dependence; tolerance means thatincreasingly large doses of the chemical are needed to achieve the same effect.

In order to put some flesh on the bare bones of the syllabus, the names of some ofthe enzymes and chemicals involved under the following sections have been included,although they are not required knowledge. These can be quite long and daunting sohave been broken up to emphasise the sense of the word - please do not feel patronisedby this, and certainly do not try to learn them!


TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 93

4.2 Dopamine and the reward pathway�

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�

�

Learning objective


• state that the reward pathway involves neurons which secrete or respond to theneurotransmitter dopamine;

• explain that dopamine induces the feeling of pleasure and so reinforcesparticular behaviours;

• explain that the reward pathway is activated by beneficial behaviour, e.g. eatingwhen hungry.

A reward is something that when supplied after a piece of behaviour causes thatbehaviour to be increased or repeated. In training, this is called reinforcement. Theneurons of the reward pathway (or system) are located in the mid-brain below thecortex, linking to the areas at the base of the cortex and in the frontal areas of thecortex. The activation of this pathway by beneficial actions such as feeding, sexualcontact, or successful aggression, must have developed very early in our evolution.

The neurotransmitter principally associated with the reward pathway is dopamine, arelatively simple organic molecule. Dopamine also plays many other roles in the brain,being involved in behaviour, cognition, punishment, motivation, voluntary movement,sleep, mood, attention, learning, and working memory. In the reward pathway, dopaminesecretion causes feelings of pleasure and euphoria (happiness and contentment). Asall types of reward seem to increase the level of dopamine secretion in the brain, agood definition of a reward would be something that increases dopamine secretion inthe reward pathway.

Dopamine and the reward pathway: Question

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Q1: Explain why linking a behaviour with activation of the reward pathway would beimportant in evolutionary terms.

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4.3 Endorphins�

�

�

�

Learning objective


• state that endorphins stimulate the neurons that are involved in reducing theintensity of pain;

• explain that increased levels of endorphins are connected with euphoricfeelings, appetite modulation and the release of sex hormones;

• state that increased endorphin production is associated with severe injury,prolonged continuous exercise, stress and consumption of certain foods.

Endorphins are opioid peptides, their name being a strong clue as to their action; it isan amalgam of ’endogenous’ and ’morphine’, and reflects the fact that their chemicalstructure and effect are very similar to that of morphine. They are a family of sometwenty compounds, which are divided into four types depending on the number of aminoacids which they contain, known as alpha- (α), beta- (β), gamma- (γ) and sigma- (σ)endorphins. Of these, the β-endorphins are the most powerful and usually act in thehypothalamus and the pituitary gland.

Endorphins attach to opioid receptors on neurons, and, depending on which type andwhere, they act to reduce pain or to increase euphoria.

When they attach to neurons connected to pain receptors (nociceptors) they act asinhibitors, making it less likely that an impulse will be transmitted. Pain is the body’smethod of telling you that you have done some damage to yourself (headaches andperiod pains aside); if that damage is severe, then the increased release of endorphinsreduces the perceived pain, helping the body to continue to function.

Another cause of increased endorphin production is prolonged intense physical activity;intense here meaning that the activity is at a level which makes breathing difficult. Oneconsequence of this is that during a hard training session, it is possible to do damagewhich only later becomes apparent. Any-one who has played a contact sport will knowhow sore an injury can seem in the hours after the game ends, even though it wasscarcely noticed when it occurred. As endorphin secretion falls, so the impulses in thepain circuits increase.

The release of endorphins during such challenging exercise also accounts for the feelingof euphoria experienced afterwards, the ’runner’s high’. This is a result of endorphins inthe reward system attaching to a different set of opioid receptors, with two outcomes:

1. firstly, the production of the inhibitory neurotransmitter GABA (gamma-amino-butyric acid) is itself inhibited so that impulses are more likely to be generated(GABA is used at the great majority of fast inhibitory synapses in nearly every partof the brain) - many sedative/tranquillising drugs act by enhancing its effects;

2. secondly, the release of dopamine is stimulated.

Together these have the effect of greatly increasing the number of impulses in the rewardpathway.



Increased endorphin production has also been linked to the consumption of darkchocolate and spicy food, both of which can become quite addictive. Sexual orgasmalso raises endorphin levels, as does the physical closeness of a loved one.

Research has also suggested that endorphins play a role in appetite modulation (thecontrol of food consumption), the release of sex hormones, and the body’s reaction tostress.

Endorphins: Questions

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Q2: Explain how endorphins reduce the sensation of pain.

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Q3: Give an example, with an explanation, of situations in which pain suppression isbeneficial and detrimental.

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Q4: The lack of a satisfying sexual relationship is a major factor in the breakdown ofmany marriages. What have endorphins got to do with this?

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4.4 Neurotransmitter-related disorders and their treatment�

�

�

�

Learning objective


• state that neurotransmitter-related disorders arise from the under- or over-production of neurotransmitters, or an imbalance in their production;

• state that many of the drugs used to treat these disorders are similar toneurotransmitters;

• explain that agonists bind to and stimulate receptors, thus mimicking theneurotransmitter;

• explain that antagonists bind to specific receptors, blocking the action of aneurotransmitter;

• state that other drugs inhibit the enzymes which degrade neurotransmitters orinhibit re-uptake.

Given the wide variety of neurotransmitters and the equal diversity of receptors,it should be unsurprising that there are a considerable range of neurotransmitter-related disorders, some of which are well known, e.g. Alzheimer’s and Parkinson’sdiseases, others less so, e.g. myasthenia gravis. There can be either over- or under-production of the neurotransmitter, or an imbalance between the production of differentneurotransmitters which operate together (e.g. one being inhibitory and the otherexcitatory). In other cases, it may be that receptors are blocked so that neurotransmitterscannot bind to them.



Consequently, many of the drugs used to treat these conditions are similar to theneurotransmitters which are present in abnormal levels.

4.4.1 Drugs used to treat neurotransmitter-related disorders

Among the drugs used to treat these disorders are agonists, antagonists and inhibitors.

Agonists are chemicals which mimic the action of a neurotransmitter by binding toits receptor and triggering a response in the corresponding neuron. Drugs which areagonists therefore have a similar effect on the natural agonist, the neurotransmitter.

Antagonists are chemicals which bind to the receptors and prevent theneurotransmitter from so doing. Similarly to enzyme inhibitors, they may exert their effectby binding to the active site of the receptor in competition with the neurotransmitter, laterseparating from the active site. However, some antagonists bind permanently to theactive site, preventing it ever subsequently receiving a neurotransmitter. Also, similarlyto enzyme inhibitors, some antagonists bind to a part of the receptor other than theactive site (an allosteric site), distorting the shape of the active site and preventingneurotransmitters from binding.

Enzyme inhibitors may be used either to act on the enzymes which breakdown the neurotransmitters at the synapse (e.g. acetyl′cholin′esterase) or whichinhibit the re-uptake of the neurotransmitter into the presynaptic neuron (e.g.nor′adrenaline/norepinephrine, dopamine).

4.4.2 Neurotransmitter-related disorders and their treatment

Although you are not required to know the details of any particular disorders or theirtreatment, a selection are included below to illustrate why particular drugs are used ineach case. It should be remembered that these are common conditions and that we willall come across them at some point in our lives, either personally or in people close tous. It should be understood that there is much current research into these conditions,and that the hypotheses about their causes and the types of treatment available areconstantly evolving.

Alzheimer’s Disease

Alzheimer’s Disease is the most common cause of dementia, i.e. the prematuredeterioration of mental faculties. Although most commonly found in people aged 65or over, it may occasionally develop much earlier. The disease causes a loss of neuronsreleasing acetylcholine in parts of the cerebral cortex and their associated mid-brainareas, and the development of clumps of amino acids known as plaques. The onsetof the condition can be delayed by taking part in intellectual activities such as bridge,chess or music, which not only help to keep the brain active, but also promote socialinteraction which can be beneficial.

There is no cure for the disease at present, but the symptoms can be ameliorated by theuse of drugs. One of these is an acetyl′cholin′esterase inhibitor, which slows the rateat which acetylcholine is degraded, thus maintaining its concentration in the synapses,despite the reduction in its production.



Parkinson’s Disease

Parkinson’s Disease is also a degenerative disorder which is most often found inpeople over 50 years old. The most obvious early symptoms of the disease areshaking, slowness and difficulty of movement. Later, there develop difficulties in mentalfunctioning. One of its causes is the failure of the mid-brain to produce sufficientquantities of dopamine as a result of cell death; towards the end of the course of thedisease, nearly three-quarters of the cells in this area may be affected. The overalleffect of this is to reduce the flow of impulses to the relevant areas of the cortex, thusincreasing the effort required to carry out any given activity.

An illustration of Parkinson’s disease by William Richard Gowers, which was firstpublished in A Manual of Diseases of the Nervous System (1886)

Again, there is currently no cure for the condition, but different drugs can ameliorate thesymptoms at any given stage in its development:

• L-DOPA (L-3,4-di′hydroxy′phenylalanine) is the precursor of the inter-relatedneurotransmitters dopamine, noradrenaline (norepinephrine) and adrenaline(epinephrine) - unlike dopamine, it can cross the blood-brain barrier in significantquantities and so can be injected into the blood stream and reach the brain, whereit is converted into dopamine;

• dopamine agonists are drugs which attach to the dopamine receptors and triggerimpulses in the relevant neurons;

• mono′amine oxidase inhibitors (MAO-B inhibitors) raise the level of dopamine byacting on the enzyme mono′amine oxidase-B, which degrades dopamine in thesynapse;

• the introduction of adult neural stem cells also represents a possible futuretreatment - these cells might be able to be introduced into the brain to replacethe lost dopamine-secreting neurons.



Schizophrenia

Schizophrenia is a condition which has both genetic and environmental origins. Thegenetic component involves the action of several genes (multifactorial inheritance), and,as such, can exert a wide range of levels of influence. The prime environmental influenceis drug abuse, with cannabis being most important, although cocaine and amphetaminesare also strongly implicated. Other environmental factors may play a role, e.g. growingup in an urban environment doubles the likelihood of the condition developing. Thetypical symptoms of schizophrenia are delusions, disordered thoughts and speech,hallucinations, poor emotional responses, limited speech, social isolation, and lack ofmotivation.

Risperidone (trade name Risperdal) is a common a typical antipsychotic medicationused in the treatment of schizophrenia

Until recently, it was thought that the neurological cause of schizophrenia was over-stimulation of the dopamine receptors in the reward pathway, which was discoveredwhen dopamine antagonist drugs were found to reduce the symptoms of the conditions.Other neurotransmitters (serotonin and glutamate) are now thought to also be involved.

Depression

Depression in the clinical sense should not be confused with feeling depressed andgenerally down about the world. Clinical depression has a serious impact on nearly allaspects of life, including relationships, work, sleep, eating and general health. Typically,the symptoms are very low mood, loss of enjoyment, and a sense of worthlessness andguilt.

There are several hypotheses about the neurological cause of depression. In particular,a part of the brain stem close to the medulla has been implicated. In this area,serotonin secretion is suggested as having a regulatory role in relation to the otherneurotransmitters norepinephrine (noradrenaline) and dopamine so that low serotoninlevels will in turn reduce their secretion. This gives the key to one approach to thetreatment of depression. Norepinephrine is reabsorbed into the presynaptic axonterminal so that its concentration is raised by drugs, which inhibit its re-uptake. Incontrast, dopamine is degraded by enzymes in the synapse so, as in the treatmentof Parkinson’s Disease, monoamine oxidase (MAO-B) inhibitors are used to increase itsconcentration.



Generalised anxiety disorders

Generalised anxiety disorders arise from a malfunction in the amygdala regions in thelower central area of each cerebral hemisphere, which are especially concerned with thefeelings of fear and anxiety. The condition is characterised by excessive and irrationallong-lasting worry about everyday matters, expressing itself in a very wide range ofsymptoms, including fatigue, breathing difficulties and insomnia.

One suggested cause is an imbalance between the neurotransmitters serotonin andnorepinephrine. One treatment may be to administer drugs which act as agonists onthe gamma-amino′butyric acid (GABA) receptors - as GABA is the principal inhibitoryneurotransmitter in the body, this has the effect of reducing the stimulation of the neuronsin the amygdale. Beta-blockers may also be used as a treatment; as their name implies,they are antagonists which attach to norepinephrine receptors (beta-receptors beingone of several types), thus reducing the excitatory effect of the neurotransmitter in theamygdala.

Neurotransmitter-related disorders and their treatment: Question

Go onlineQ5: Complete the following table about neurotransmitter-related diseases.

DisorderArea of brain

affectedNeurotransmitters

involvedDrug Treatment

Alzheimer’sdisease

Parkinson’sdisease

Schizophrenia

Generalisedanxiety disorder

Depression

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



4.5 Mode of action of recreational drugs�

�

�

�

Learning objective


• explain that many recreational drugs affect neurotransmission in the rewardpathway;

• state that changes in neurochemistry alter mood, cognition, perception andbehaviour;

• state that recreational drugs may:

◦ stimulate the release of neurotransmitters;

◦ imitate the action of neurotransmitters (agonists);

◦ block the binding of neurotransmitters to their receptors (antagonists);

◦ inhibit the re-uptake of neurotransmitters;

◦ inhibit the enzymatic degradation of neurotransmitters.

Drugs which are referred to as recreational are introduced into the body either becausethey generate pleasurable sensations in of themselves, or because they enhance someother leisure experience. They are also taken in other circumstances, e.g. to help copewith pain or other conditions.

The list of chemicals which may be consumed in this way is staggering, and everexpanding. In nearly all cases, the use or possession of these substances is illegalin all countries. Major exceptions are the mild stimulants caffeine (tea, coffee, cocoa)and nicotine (all forms of tobacco), and the depressant ethanol. The use of caffeineis universally unregulated (although proscribed by certain religions), whereas theavailability of tobacco and alcohol are usually regulated to some extent. All threeare addictive and higher levels of intake are needed to achieve the same effect withcontinued use (otherwise known as tolerance). So-called ’legal highs’ are usuallynewly synthesised compounds related to existing illegal ones or newly discovered plantsubstances. The fact that the law has not caught up with them does not indicate thatthey are safe to consume!

Caffeine

Caffeine is the mostly widely used psychoactive drug in the world. It does not attractlegal restrictions because its stimulant effects are relatively mild. Nevertheless, it doesraise blood pressure and disrupts sleep, both of which can lead to serious complications.The classic image below of the effect of caffeine on a spider’s efforts to spin a web shouldgive us pause for thought.



The effect of caffeine on spider web construction(Noever, R., J. Cronise, and R. A. Relwani. 1995. Using spider-web patterns to

determine toxicity. NASA Tech Briefs 19(4))

Ethanol

Ethanol is the most widespread drug which is abused. In those countries where itsconsumption is legal, it is frequently drunk in quantities which are potentially harmful, itslong-term consumption causes considerable expense to health services, and the sideeffects on society of its misuse in terms of violence (domestic and otherwise), crime andloss of working time are huge. It is probable that it only remains legal because its useis so widespread and deeply woven into society that the public support that would berequired to make a ban successful would be lacking (as was the case in the USA duringthe Prohibition years of the 1920s).

Tobacco

While not having the social dimension of alcohol abuse, smoking tobacco causesserious damage to the smoker’s health and to those around them. For this reason,the practice is being increasingly regulated in many parts of world. Unlike ethanol, thenicotine stimulant present in tobacco is not the cause of the health problems, in thesense that the strong addiction which quickly develops does not itself damage health.Rather, it is the actual smoking process which releases a wide range of chemicals whichcause cancers, and pulmonary and cardiovascular disease.

4.5.1 Modes of action

Most recreational drugs target the brain’s reward system, directly or indirectly, and causeit to be flooded with dopamine. When some drugs are taken, they can cause dopaminesecretion at levels up to ten times those caused by natural rewards, which stronglymotivates people to repeat the act. In a sense, this unnatural over-stimulation of thereward circuit will teach us to abuse drugs. This quickly leads to addiction and so, bydefinition, all recreational drugs are addictive.

As mentioned in an earlier section, while the effect of increased dopamine secretionin the reward pathway is to cause feelings of pleasure and euphoria, dopaminealso plays many other roles in the brain, being involved in behaviour, cognition,punishment, motivation, voluntary movement, sleep, mood, attention, learning, andworking memory. Consequently, the effects of recreational drugs run far beyond the



immediate sensations for which they are consumed, having widespread and profoundeffects on the neurochemistry of the brain.

The modes of action of recreational drugs are very similar to those of the drugs used totreat neurotransmitter-related disorders.

Stimulating the release of neurotransmitters

MDMA (ecstasy) increases the level of the neurotransmitter serotonin by stimulating itsrelease from the synaptic vesicles of neurons, and also inhibiting its re-uptake. Theincreased secretion of serotonin in the reward pathway in turn stimulates increasedproduction of dopamine and norepinephrine, with their associated euphoric effects.

Nicotine binds to certain acetylcholine receptors, stimulating the production of severalneurotransmitters including dopamine, which leads to the feelings of euphoria andrelaxation, and to addiction. In addition, nicotine stimulates the secretion ofadrenaline/epinephrine, thus causing increases in blood pressure, breathing and heartrates, and higher blood sugar levels.

Agonists

Cannabis attaches to receptors in the neurons of the brain which naturally bind theendocannabinoid neurotransmitters produced in the brain. These receptors arelocated on the presynaptic neuron. The effect of their binding to cannabis is to suppressthe secretion of the inhibitory neurotransmitter GABA, thus increasing stimulation ofimpulses in the reward pathway.

Ethanol acts as an agonist in the central nervous system by binding to the GABAreceptors, depressing the flow of impulses in the postsynaptic neuron. The more GABAreceptors that are stimulated, the less the chance of an impulse being generated. AsGABA is the most widespread neurotransmitter which causes inhibition in the brain, thisexplains the effect of ethanol on so many different aspects of behaviour.

Antagonists

Ethanol is also an antagonist of the glutamate receptor NMDA which plays a key rolein memory; this is thought to explain the memory loss associated with even quite lowlevels of alcohol consumption.

Inhibition of re-uptake of neurotransmitters

Cocaine blocks the re-uptake of serotonin, norepinephrine and dopamine by bindingto the transporter molecules that effect their re-absorption into the presynaptic neuron.Consequently, the levels of these chemicals are increased in the synapses, but theactual effect depends on the cells in which the receptors are located.

Inhibition of degradation of neurotransmitters

As well as nicotine, tobacco smoke contains two monoamine oxidase (MAO) inhibitors.Due to the fact that MAOs are the enzymes which break down the neurotransmittersdopamine, norepinephrine and serotonin, the effect is to boost the euphoric sensationassociated with tobacco smoking and cause most of its addictive properties.



Modes of action: Question

Go onlineQ6: Complete the following table about the mode of action of drugs.

Mode of action Drug Neurotransmitter

Stimulating the release ofneurotransmitters

Agonists

Antagonists

Inhibition of re-uptake ofneurotransmitters

Inhibition of degradation ofneurotransmitters

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.6 Drug addiction, sensitisation and tolerance�

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Learning objective


• state that changes in the number and sensitivity of receptors underlie addictionand tolerance;

• state that sensitisation is an increase in the number and sensitivity of receptors;

• state that sensitisation results from exposure to antagonist drugs;

• state that sensitisation leads to addiction;

• state that desensitisation is a decrease in the number and sensitivity ofreceptors;

• state that desensitisation results from exposure to agonist drugs;

• state that desensitisation leads to tolerance.

Whereas the hyperstimulation of the reward pathway generates a psychologicaldependence on a drug (often after only a few encounters with it), long-term abuse ofa drug leads to changes in the nervous system which make the addiction physiologicalas well. This may take two forms.



• Sensitisation, in which the effect of the drug increases with repeated exposureto it, i.e. the same dose has an increased effect the more often it is taken. At thelevel of the neurons, the effect results from an increase in the number of receptorsand an increase in their sensitivity to the drug. This is caused by drugs that act asantagonists and is associated with the severe withdrawal symptoms experiencedwhen giving up some drugs, e.g. alcohol.

• Desensitisation, in which the effect of the drug reduces with repeated exposure.In this case there is a decrease in the number and sensitivity of receptors, andthe drugs involved are agonists. The result is drug tolerance, in which increasingdoses of the drug are required to achieve the same effect, e.g. heroin.

Drug addiction, sensitisation and tolerance: Questions

Go online

Q7: What underlies drug addiction and tolerance?

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Q8: What causes sensitisation?

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Q9: What drugs cause sensitisation?

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Q10: To what does drug sensitisation contribute?

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Q11: What causes desensitisation?

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Q12: What drugs cause desensitisation?

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Q13: What does desensitisation cause?

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.7 Learning points

Summary

Dopamine and the reward pathway

• The reward pathway involves neurons which secrete or respond to theneurotransmitter dopamine.

• Dopamine induces the feeling of pleasure and so reinforces particularbehaviours.

• The reward pathway is activated by beneficial behaviour, e.g. eating whenhungry.

Endorphins

• Endorphins stimulate neurons involved in reducing the intensity of pain.

• Increased levels of endorphins are connected with euphoric feelings,appetite modulation and the release of sex hormones.

• Increased endorphin production is associated with severe injury, prolongedcontinuous exercise, stress and consumption of certain foods.

Neurotransmitter-related disorders and their treatment

• Neurotransmitter-related disorders arise from the under- or over-productionof neurotransmitters, or an imbalance in their production.

• Many of the drugs used to treat these disorders are similar toneurotransmitters.

• Agonists bind to and stimulate receptors, thus mimicking theneurotransmitter.

• Antagonists bind to specific receptors, blocking the action of aneurotransmitter.

• Other drugs inhibit the enzymes which degrade neurotransmitters or inhibitre-uptake.

Mode of action of recreational drugs

• Many recreational drugs affect neurotransmission in the reward pathway.

• Changes in neurochemistry alter mood, cognition, perception andbehaviour.

• Recreational drugs may:



Summary continued

◦ stimulate the release of neurotransmitters;

◦ imitate the action of neurotransmitters (agonists);

◦ block the binding of neurotransmitters to their receptors (antagonists);

◦ inhibit the re-uptake of neurotransmitters;

◦ inhibit the enzymatic degradation of neurotransmitters.

Drug addiction, sensitisation and tolerance

• Changes in the number and sensitivity of receptors underlie addiction andtolerance.

• Sensitisation is an increase in the number and sensitivity of receptors.

• Sensitisation results from exposure to antagonist drugs.

• Sensitisation leads to addiction.

• Desensitisation is a decrease in the number and sensitivity of receptors.

• Desensitisation results from exposure to agonist drugs.

• Desensitisation leads to tolerance.



You should have a good understanding of the mode of action of recreational drugs beforeattempting the question.


Extended response question: The mode of action of recreational drugs

15 min

Give an account of the mode of action of recreational drugs (with examples), under theheadings:

A) effects on the brain; (4 marks)

B) modes of action. (6 marks)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .




End of Topic 4 test

Go online


The reward pathway involves neurons which secrete ��, which induces thefeeling of pleasure and so �� particular behaviours. The reward pathway isactivated by �� behaviour.

�� stimulate neurons involved in reducing the intensity of pain. Increased levelsof endorphins are connected with appetite ��. �� endorphin productionis associated with the consumption of certain foods.

Many of the �� used to treat neurotransmitter-related disorders are similar toneurotransmitters. �� bind to and stimulate receptors, thus �� theneurotransmitter. �� bind to specific receptors, so �� the action of aneurotransmitter. Other drugs inhibit the enzymes which �� neurotransmitters,or inhibit reuptake.

Word list : agonists, antagonists, beneficial, blocking, degrade, dopamine, drugs,endorphins, increased, mimicking, modulation, reinforces.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Many recreational drugs affect neurotransmission in the perception andbehaviour.

Changes in neurochemistry alter mood, cognition, reward pathway.

Recreational drugs may stimulate the agonist drugs.

Recreational drugs may inhibit the agonists.

Drugs which imitate the action of neurotransmitters are tolerance.

Drugs which block the binding of neurotransmitters are release ofneurotransmitters.

An increase in the number and sensitivity of receptors is re-uptake ofneurotransmitters.

Sensitisation results from exposure to addiction.

Sensitisation leads to antagonists.

A decrease in the number and sensitivity of receptors is sensitisation.

Desensitisation results from exposure to antagonist drugs.

Desensitisation leads to desensitisation.



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Q16: Which neurotransmitters are involved in reducing the intensity of pain? (1 mark)

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Q17: List three factors that increase their production. (3 marks)

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Q18: Which neurotransmitter is involved in the reward pathway? (1 mark)

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Q19: What feelings does activation of the reward pathway engender? (1 mark)

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Q20: What is the difference between agonists and antagonists? (2 marks)

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Q21: State two other ways that drugs may be used to ameliorate neurotransmitter-related disorders. (2 marks)

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Q22: What part of the brain do recreational drugs affect? (1 mark)

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Q23: What do the changes in neurochemistry caused by recreational drugs alter? (3marks)

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Q24: List five ways that recreational drugs exert their effect on neurotransmitters. (5marks)

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Q25: What causes drug sensitisation?(1 mark)

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Q26: What type of drug is involved in sensitisation? (1 mark)

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Q27: What does drug sensitisation lead to? (1 mark)

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Q28: What causes drug desensitisation? (1 mark)

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Q29: What type of drug is involved in desensitisation? (1 mark)

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Q30: What does drug sensitisation lead to? (1 mark)

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109

Topic 5

Infant attachment and the effect ofcommunication

Contents

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

5.2 Forms of infant attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

5.2.1 Infant attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

5.2.2 Imprinting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

5.2.3 Social compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

5.3 Long period of dependency . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

5.3.1 Parental control methods . . . . . . . . . . . . . . . . . . . . . . . . . . 118

5.4 The effect of communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

5.4.1 Information transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

5.5 Non-verbal communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

5.5.1 Infant bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

5.5.2 Adult . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

5.6 Verbal communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

5.6.1 Language differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

5.6.2 Acquiring language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

5.6.3 Development of language . . . . . . . . . . . . . . . . . . . . . . . . . . 124

5.6.4 Mathematical notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

5.7 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127


5.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Learning objectives


• explain that behaviour is influenced by the inter-related factors of inheritance,maturation and experience;

• explain the development and significance of infant attachment;

• describe forms of non-verbal communication and explain its role;

• explain the nature and significance of verbal communication through language.

110 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION

5.1 Introduction

Behaviour is the response of an organism to internal and external stimuli. The natureof this response is determined by the interaction of three factors: inheritance, maturationand experience.

Inheritance

Some aspects of the behaviour of all animals are determined by their genes. Thosewith a short life history, or, more correctly, short stages in it, simply do not have timeto adapt behaviour as a result of their experience of the environment. Consequently,their responses to stimuli must be programmed in their genes. For example, the LargeWhite butterfly, which is common in most of Scotland, has a period of just a few weeksas an adult in which to find a mate and then locate suitable plants on which to lay itseggs. Making a mistake would mean that no offspring will be produced, wasting all ofthe resources that have gone into getting the animal through the previous stages of itslife cycle. Only genes which induce the appropriate behaviour will pass into the nextgeneration.

Other insects that live longer as adults do show the ability to learn, albeit within a verylimited context. Honey bee workers, which can live from six weeks to six months asadults (depending on the time of year), learn to recognise new scents very quickly, anability that is obviously related to their task of finding nectar and pollen from whateverflowers are available at a particular time of the year.

Humans lie at the other end of this spectrum, with a very high proportion of theirbehaviour which is developed as a result of experience. Compared to other animals,we live a long time and spend a greater proportion of our lives as juveniles in the careof adults. This provides endless opportunities to observe and copy, and to experimentwith alternative responses. Learning to communicate by means of language is a goodexample; children usually begin to utter intelligible words and simple sentences duringtheir second year, and most children can conduct quite complex conversations by theage of three. This is an ability that our closest Primate relatives, the chimpanzees, donot possess.

At the simplest level of human behaviour are the reflexes, e.g. knee jerk (assistingthe regaining of balance) or blinking (protecting the eye). These are rapid, automatic,protective responses that are common to all humans, and many are present from birth.Some of these are only found in the first few months of life, e.g. the palmar grasp reflex,by which the baby curls its fingers tightly around any object placed against its palm.

It is now thought that genetics plays a significant role in much more of our behaviourthan was previously imagined, contributing to many of our decisions in life (e.g. choiceof mate).

Maturation

As mentioned in the previous section concerning the structure of the nervous system,the presence of a myelin sheath greatly increases the rate of impulse transmission byneurons. In newborn infants, the degree of myelination is relatively low; with the passingmonths, more and more neurons develop the myelin sheath, and thus reactions becomemuch faster. This accounts for the developmental stages observed as infants progressfrom sitting, to crawling, standing, and eventually walking. Also, the slow developmentof myelination in the hippocampus explains why we do not have memories from our first


TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION 111

two years of life.

The profound physiological changes associated with puberty are likewise expressedin behaviour. This involves not just the obvious interest in matters sexual, but alsochanging tastes. Children generally like sweet things, whereas adults are more likely toprefer sharper tastes, e.g. mustard or olives.

Environment

If it is accepted that humans depend for the development of a large part of theirbehaviour on learning, i.e. changing behaviour in the light of experience, then it followsthat the nature of that experience will influence the behaviour that ensues. Two examplesillustrate this.

1. As mentioned above, children usually start to talk by the age of two, and by threehave quite a complex grasp of their language. Of course, in different countriesand cultures, children learn different languages. If identical twins are separatedat birth as a result of some tragedy, and subsequently reared in different cultures,they learn different languages. Humans possess a genetically determined abilityto learn language, but the actual tongue that is learned depends on the child’sexperience.

2. In the same way, all human cultures have developed music, and all humans have(to a varied extent, admittedly) the ability to develop musical skills. Most commonly,that is expressed through song, but could equally be by means of the ability toplay musical instruments, some of which are closely associated with one culture,e.g. the didgeridoo, which is associated with the Australian Aboriginal people, thebalalaika with Russia, and the bagpipes with Scotland (and Brittany, the Basquecountry, and several other places, including parts of England!).

An Estonian bagpiper



5.2 Forms of infant attachment�

�

�

�

Learning objective


• explain that early infant attachment is important in laying the foundation for thefuture formation of stable relationships;

• state that attachment becomes evident between six and nine months after birth;

• explain the ’strange situation’ procedure;

• describe the responses to the ’strange situation’ procedure as secure andinsecure attachment, detachment, anger, and inconsistent responses;

• state that infants who form secure attachments are more likely to investigatetheir immediate environment, which helps the development of their cognitiveabilities.

In all mammalian species, the youngster is instantly identified as such. A young wild pighas a short snout and a striped body with a curly tail, as well as being much smaller thanan adult. A red deer calf has a dappled coat. Somehow, these attributes invite caring inthe parent. Furthermore, they can prevent a big, ugly carnivore which hasn’t eaten forfour days from seeing a small relative as a tender meal!

Small, furry animals look cute and evoke feelings of parenting. Thus, there is oftenstrong bonding between humans and their pets, and between youngsters and cuddlytoys. Is this more apparent in girls than in boys?

If you think of a human child, you think of a head that is greatly out of proportion to thesmall limbs, a small nose, large eyes, and a very affectionate personality. Thesefeatures have not evolved by accident. Nor have the ways in which a babycommunicates. Crying, clinging and suckling all communicate dependency. A strong,mutual, emotional attachment develops between the baby and its carers. The mother,or mother-figure, in particular must be very alert to read these signals from her baby.The child cannot talk, but is still very active in communicating its needs and desires.Infant attachment develops, at first indiscriminately, but often becoming specific to oneparent or another at different times during the child’s development.

5.2.1 Infant attachment

Infant attachment offers time for a child to observe closely, and to learn. When the childis facing a parent, it can observe and imitate facial expressions, body language and lipmovements that form words. When facing a third party, the child observes and copiesreactions to these cues.

Thus, a long period of dependency, part of which occurs while the brain continues togrow, allows opportunities to learn communication, social and language skills in aprotective environment. Informed decisions can be made with the benefit of learning bymeans of experience in safe surroundings.



In a series of experiments, conducted between 1963 and 1968, Dr. Harry Harlowoffered young rhesus monkeys a choice between two surrogate ’mothers’. In the firstgroup, the terrycloth (essentially a cloth toy) mother provided no food while the wiremother did, in the form of an attached baby bottle containing milk. In the second group,the terrycloth mother provided food while the wire mother did not. It was found that,when frightened, the young monkeys clung to the terrycloth mother whether it providedthem with food or not, and that the young monkeys chose the wire surrogate onlywhen it provided food. Apparently the terrycloth mothers provided something that wasmore valuable to the young monkeys than food. She was providing contact comfort.Harlow’s interpretation was that the preference for the terrycloth mother demonstratedthe importance of affection and emotional nurturance in mother-child relationships.

Dr. Harry Harlow’s surrogate ’mothers’

5.2.2 Imprinting

It was initially thought that there was one critical period during which a baby had toimprint onto an adult to securely form an ’infant attachment’. More recent work hasshown that imprinting occurs at several sensitive periods.

It is difficult to investigate infant behaviour for ethical reasons. Researchers use otheranimals instead. In fact, information about the sequence of stages in the developmentof walking in humans was partly gleaned from experiments on pigeons. Newly fledgedbirds were confined in cardboard tubes until their siblings could fly. The restrained birdscould fly at the same time as their peers without having had practice at stretching theirwings at all! One investigation of infant attachment which has been deemed ethical isthe ’strange situation’ experiment, which requires video equipment, three adults, aparent/carer and one subject, an infant child.



The ’strange situation’ is a laboratory procedure which is used to assess infantattachment that was first developed by Mary Ainsworth, a Canadian developmentalpsychologist, in the 1970s. The procedure consists of the following eight episodes:

1. the parent and infant are introduced to the experimental room;

2. the parent and infant are alone - the parent does not participate while the infantexplores;

3. a stranger enters, converses with the parent, then approaches the infant - theparent leaves, inconspicuously;

4. the ’first separation episode’: the stranger’s behaviour is geared to that of theinfant;

5. the ’first reunion episode’: the parent greets and comforts the infant, then leavesagain;

6. the ’second separation episode’: the infant is alone;

7. continuation of the ’second separation episode’: the stranger enters and gearsbehaviour to that of infant;

8. the ’second reunion episode’: the parent enters, greets the infant, and picks upthe infant; the stranger leaves.

Episode 3 of the ’strange situation’ procedure

Four aspects of the child’s behaviour are observed:

1. the amount of exploration (e.g. playing with new toys) that the child engages inthroughout;

2. the child’s reactions to the departure of its parent;

3. stranger anxiety (when the baby is alone with the stranger);

4. the child’s reunion behaviour with its parent.



Of these, the last is given most weight in determining the category to which the infant’sbehaviour belongs.

The ’strange situation’ experiment is carried out on 12 to 18 month old children, whohave reached a level of maturation when they can determine that a stranger is ’foreign’.The developers of this procedure grouped children into four categories:

1. securely-attached - children play comfortably and are friendly to strangers whentheir parent is present, but become distressed in her absence;

2. insecurely-attached, avoidant - children pay little attention to the parent and arenot distressed in her absence; they appear quite detached;

3. insecurely-attached, resistant - children cling to the parent and are distressed inher absence; they seek reassurance, but reject contact when the parent returnsand can become angry;

4. disorganised attachment - children show inconsistent and contradictoryresponses; they may freeze for substantial periods, show very stereotyped orcontradictory behaviour, e.g. they may cry when the parent is away, but then avoidher on her return and appear to be afraid of her.

Securely-attached children have parents or carers who are attentive, skilled at readingthe child’s needs, and promote socialisation. The parents of insecurely-attachedchildren respond more to their own moods and wishes, ignoring their children’s needs.A disorganised response tends to reflect abnormal parenting, including abuse, andchildren with a disorganised response are more prone to psychological disorders.Alternatively, an early secure attachment tends to have a lasting positive influence,the children being more likely investigate their environment, helping their cognitivedevelopment.

In today’s society, primary carers are often nursery nurses or child-minders. They mustbe aware of fulfilling parental wishes whilst ensuring confident progress in their charges.

Imprinting: Question

Go online

Q1: Arrange the stages of the ’strange situation’ procedure in the correct order.

• Continuation of second separation episode: Stranger enters and gears behaviourto that of infant.

• First reunion episode: Parent greets and comforts infant, then leaves again.• First separation episode: Stranger’s behaviour is geared to that of infant.• Parent and infant are alone. Parent does not participate while infant explores.• Parent and infant are introduced to the experimental room.• Second reunion episode: Parent enters, greets infant, and picks up infant; stranger

leaves.• Second separation episode: Infant is alone.• Stranger enters, converses with parent, then approaches infant. Parent leaves

inconspicuously.

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5.2.3 Social compensation

Although children can suffer delays in language learning and in other social skills ifdeprived of social contact and stimulation during infancy, they are extremely adept atcompensating for this lack of development. Humans are extremely adaptable and canrecover from setbacks.

Although it is true that infant attachment has an important influence on laterdevelopment, local child-rearing customs and the temperament of the child may havesignificant bearing on the way in which an infant responds to the ’Strange Situation’mentioned in the previous section. If a child is used to very close physical contact witha carer and has little experience of free play or visits by strangers, she will inevitablyrespond with concern to a new situation such as this.

We cannot be sure that it is simply early socialisation that gives a child security later inlife. Parents who are responsive to their children’s needs in infancy are likely to furtherimbue confidence in later years. It is also likely that children can learn socialcompetence by imitating their peers.

However, other studies have confirmed the value of the initial ’Strange situation’investigation. In one study, two year old children were shown to have more competencein the use of tools the more securely attached they had been at an earlier age. Theyapproached problem solving with enthusiasm and persistence whilst seeking adult helpwhen required. Insecurely-attached children became frustrated and angry easily. Theyrefused adult help and gave up trying fairly easily.

In another study, 15-month-old children were rated for infant attachment. They werethen observed at an age of 40 months and their social behaviour was assessed. Thoserated as securely-attached tended to be social leaders and were eager to participate.Insecurely-attached children tended to be socially withdrawn and hesitant.



5.3 Long period of dependency�

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Learning objective


• state that humans have a relatively long period when they are dependent onadults;

• explain that the long period of dependency provides opportunities forsocialisation and learning;

• state that different methods of control during a child’s development can influencesocial competence;

• explain that authoritative control (providing direction) generally results in greatersocial competence than authoritarian or permissive control.

A long period of dependency offers opportunities and time for learning.

Large brains are essential for development of the discriminatory skills required torecognise other animals and learn from observation. Humans require to be adept atcommunication because of their complex social structures. However, we do not stayin the womb long enough for our brains to grow completely. Thus, in a sense, humanbabies are born prematurely compared to some mammals, which are much more highlydeveloped at birth, e.g. horses. We still have lots of maturing to do before we will beindependent, and the long period of dependency required for growth and maturationoffers many opportunities for learning.

The development of increased brain power, the evolution of higher level communicationskills, and the development of large eyes and a complex sensory system are allinterlinked. The need for well-developed senses requires a large brain, but the largebrain would have no function without the developed sensory system. Similarly, thecomplex communication skills that developed in tandem require a large brain, but alsodrive forward the evolution of such a brain.

An animal that leads a predominantly solitary lifestyle, such as a male otter, has tolearn the basic techniques of hunting and finding suitable habitat from its mother, butis required to develop relatively little social skill beyond that which is necessary to finda mate and defend its territory. A social animal, such as a human, must learn all thesubtleties of interaction that allow the individual to effectively interact with its social groupand secure its supply of life’s essentials.

The timescale required for development of these skills offers years of opportunities tointegrate into a social structure. The more skills a child develops, the easier it is tointegrate. The average Scot spends the first 25% of their life learning directly from theirparents and other adults. A house mouse, in comparison, is independent of its motherafter three weeks, which might be only 6% of the life-time of a mouse surviving to fullmaturity.



Long period of dependency: Question

Go online

Q2: State and explain two reasons for the long period of dependency in humans.

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5.3.1 Parental control methods

The methods that parents use to control and guide the behaviour of their children canbe classified under three headings: authoritarian, permissive and authoritative.

The authoritarian parent demands obedience from their children. It should not beassumed that this is an uncaring approach. Rather, it stems from the parent’s beliefthat they know what is best for the child and that it is in the child’s best interests tobehave as the parent requires. This style tends to also be associated with the use ofpunishments for failure in order to reach the required standards, a lack of involvementof the child in decision-making, and a lack of responsiveness to the child’s emotionalneeds.

The permissive parent, in complete contrast to the authoritarian one, is reluctant toimpose rules and standards, preferring to let their child regulate its own behaviour.Again, this is not an uncaring approach, but one based on the philosophy that thechild will develop best if it is allowed to make its own decisions about its behaviour,reaching decisions based on its own experience and wishes. Punishment is not partof this regime, but involvement in decision-making and responsiveness to the child’sopinions are paramount. This style is also known as indulgent parenting.

The authoritative parent uses aspects of both of the preceding styles. Standards andlimits are set by the parent, but these are explained to the child, and the child’s point ofview is respected and taken into account in decision-making. The authoritative parentexpects maturity and cooperation, offering children lots of emotional support.

A fourth category can also be identified, in which the parent neither sets standards nortakes the child’s views into account, providing no emotional support. This is known asneglectful parenting.

Research has shown that authoritative parenting is significantly the most successfulapproach in terms of developing social competence. Its products (i.e. children) arelikely to have a higher self-esteem and sense of well-being, to enjoy better health andshow less problematic behaviour, and to gain higher academic qualifications. Whilethis may generally be the case, it is also true that there are significant exceptions, e.g.the children of certain religious or racial groups, often seen as rather authoritarian, aredisproportionately high academic achievers.



Parental control methods: Questions

Go onlineQ3: Complete the table, which shows the combinations of behaviour characteristic ofdifferent methods of parental control, using the listed terms.

Demanding Undemanding

Responsive

Unresponsive

Terms: authoritarian, authoritative, neglectful and permissive.

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Q4: In what ways does authoritative parenting differ from:

i. authoritarian parenting;

ii. permissive parenting?

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5.4 The effect of communication

Non-verbal communication is an important part of parent-infant bonding and in adultcommunication.

Communication is simply an exchange of information. It occurs among all animals, and,in some cases, warning calls used by one species (e.g. monkeys) which are specific toone particular danger, such as a snake or an eagle, are recognisable as such by otherspecies. Communication does not always require a vocabulary of words.

5.4.1 Information transfer

Information can be passed both intentionally and unintentionally by verbal and non-verbal language. Non-verbal communication consists of body language which is oftenunconscious, including grimaces and other facial movements, and gestures, which areoften under conscious control.

When a baby smiles at her mother, a boy mirrors his girlfriend’s posture or your eyeslight up when the teacher enters the room, non-verbal communication is taking place.Friendship and intimacy are often signalled as much by non-verbal clues as by thecontent and context of conversation. Eye contact lasts longer, proximity is closer, andmay include touching, and smiling is more frequent when we are with close allies.

We must be careful as we may often read non-verbal communication according to ourown moods or needs rather than those intended by the author. In addition, a skilledpractitioner, not always a magician by trade, can easily mis-communicate informationby redirecting an observer’s gaze or by giving a false sense of security usingnon-verbal language.



Information transfer: Question

Go onlineQ5: Put the communication methods listed into the correct categories in the table:

VerbalNon-verbal -

Body languageNon-verbal -

Gesture

Communication methods: feeling your collar when under pressure; indicating that anarcher’s bow finger will be cut off if he gets caught; pointing to your nose when playingcharades; shouting out; showing whites of eyes when angry; sobbing loudly; talking;throwing a fist in the air; walking with an expanded chest after a victory.

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5.5 Non-verbal communication�

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Learning objective


• explain how non-verbal communication contributes to the formation ofrelationships between individuals;

• state that non-verbal communication can signal attitudes and emotions;

• state that non-verbal communication acts as an aid to verbal communication.

This section is divided into sub-sections about communication in infants and then inadults.

5.5.1 Infant bonding

During the growth of relationships, bonding occurs when a child smiles at a parent, orwhen a couple mirror one another’s expressions or posture. This establishes strongemotional ties. Protective feelings are promoted and these behaviours have a survivalvalue for the participant. Positive feedback ensues and so a child cooing at her parentwill elicit further caring responses.

When a parent responds by smiling, vocalising (often in a high-pitched, sing-song voicewhich is encouraging to the child) and handling the infant, the child will respond insimilar fashion. From around four months, the infant recognises and prefers familiarfaces and responds more to these than to others.

Facial expressions are much more important to apes, and especially to ourselves, thanto other species. Whereas other animals walk side to side to size one another up,humans observe facial expressions with concentration. This is particularly important in



infants and in adolescents, perhaps explaining why a tiny facial spot can cause suchpanic in a teenager’s heart!

This is because we communicate so much by our facial expressions, and by lip andtongue movements. We observe speech at the same time as listening to it. ’Read mylips’ sounds trite, but is rife with meaning.

5.5.2 Adult

In adults, non-verbal communication remains of huge importance. Even seeminglymeaningless noises convey information about emotions and attitudes. Speech soundssuch as "och" and "d’oh" in variants of the English language, or "ben" and "boff" inFrench, inform the observant listener. These sounds and inflections of the voice aresometimes referred to as para-language. Voice inflections are particularly crucial inlanguages, such as Chinese, where one word can have several meanings, dependingon inflection and pitch.

Shifting eyebrows, nodding, lack of eye contact, tears, and even sweating offer positiveor negative feedback during a conversation, providing information which should not beignored, neither by the speaker nor by the listener.

Body language and gestures, such as verbal language, are culturally rooted. Aspreviously mentioned, cultures vary across distances and across time. Beware! Agesture deemed friendly in your culture may be extremely aggressive or insulting inanother.

Sometimes, as adults, we have to repress our natural communication skills. A parentwill often try to convey a feeling of well-being to children even though she, herself, isconcerned about something.



Facial expressions

Go online

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Body language across the world

Go online20 min

Web sites about body language across the world

Access the websites listed below to compare how body language differs across theworld.

• http://www.everythingesl.net/inservices/body_language.php: compares cultures;

• http://www.ai.mit.edu/projects/sociable/facial-expression.html: a robot that makesfaces;

• http://italian.about.com/library/weekly/aa062001a.htm: speaking Italian with yourhands.

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http://www.everythingesl.net/inservices/body_language.php

http://www.ai.mit.edu/projects/sociable/facial-expression.html

http://italian.about.com/library/weekly/aa062001a.htm


5.6 Verbal communication�

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Learning objective


• state that language uses symbols to represent information;

• explain that language enables information to be organised into categories andhierarchies;

• state that this organisation of information accelerates learning and intellectualdevelopment;

• explain that the ability of humans to communicate verbally has resulted in thetransmission of knowledge, development of culture and social evolution.

Humans differ from all other species in the complexity of their spoken language and intheir ability to use verbal language, i.e. words and sentences rather than just sounds,whether written or spoken. In contrast to the vagueness of some body language, verballanguage transmits complex information in a clear, concise and unambiguous manner.In addition, dialogue, in the form of questions and answers, can supplement and clarifycommunication.

Rules for combinations of symbols or words developed. These are known as syntax.These rules vary from culture to culture and evolve with usage through time. Thehistory of associated cultures can be clearly observed in the similarities between onelanguage and another. For example, French, Spanish, Romanian and English all seemto be derived from Latin.

5.6.1 Language differences

Differences also occur between language used in school (by the establishment) andthe language of the playground. Knowledge of the patois gives a quick reference pointdefining age, interests and position in the local hierarchy.

Syntax provides a framework which allows language to be constructed from phrasesencoded in memory. Nouns, verbs, adverbs, adjectives and phrases each have sensein their own right. They can then be combined in a variety of ways to give sentenceswhich have meanings of their own. This is known as semantics. To create language,thoughts that are represented by words are built into phrases which form sentences.These are governed by rules of syntax, which an infant has to somehow internalisewhile simultaneously growing a nervous system! A child has an enormous capacity toacquire vocabulary and to glean the rules of syntax and grammar. By the age of six, achild typically has a vocabulary of some 15,000 words. Learning the rules of semanticstakes rather longer...



Consider the situation where a teacher describes your project as being "outstandingwork".

Ambiguity of language - which is it?

5.6.2 Acquiring language

The website http://www.pnas.org/cgi/content/full/98/23/12874 gives an interestinginsight into the problems faced by infants in acquiring language and the success thatthey have from the age of around seven months in overcoming them.

As we grow older, the number of facts that require to be memorised rises exponentially.Our brains compensate by using language rules to construct hierarchies ofunderstanding. Using complex language allows us to learn and develop intellectually.We can aid our brains by putting burdens on the mind. By creating hierarchies as youmemorise your work you will assist your brain in encoding, storing and retrievinginformation.

5.6.3 Development of language

The symbols used to construct spoken language can be converted to written symbols.At some pre-historic time, man began to record debts and harvests as a series ofsymbols; perhaps in order that feudal lords, who did not live close enough to overseetheir vassals in a rapidly-expanding population, could keep track of their dues. Usingdifferent symbols, or hieroglyphics, in different cultures, written language developed inthe same way that a variety of spoken symbols evolved to represent the same items indifferent geographical areas. This development would inevitably have a consequentialeffect on spoken language because both were required to become more precise aboutchattels and populations.

Greek letters Chinese symbols for love

α,β,γ,δ,

. . . Δ,Σ,Ω


http://www.pnas.org/cgi/content/full/98/23/12874


The Rosetta Stone which, with text in Ancient Egyptian, and translations into Demoticand Greek, first enabled the Egyptian hieroglyphs to be interpreted

Who is ’in’ and who is ’out’ of your crowd?

10 min

Navigate to the following website: http://www.ruf.rice.edu/~kemmer/Words/shibboleth.html

Words and pronunciations let us know who is ’in’ and who is ’out’ of our crowd. Make alist of words that describe what is important in your local sub-culture.


http://www.ruf.rice.edu/~kemmer/Words/shibboleth.html

http://www.ruf.rice.edu/~kemmer/Words/shibboleth.html


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5.6.4 Mathematical notation

Many centuries ago, Chinese and Greek scholars developed mathematical notation,such as algebraic symbols, as a special type of language. Language had already provedits worth as a means of codifying information. Symbols allow organisation of informationinto categories and hierarchies.

Mathematicalsymbols

≡,∑

, ⊥, ∝, =, ∠, ≈, ∞, ±

Logic symbolsin electroniccircuits

Language developed as a form of communication between people who were presentsimultaneously. Crucially, we can now communicate verbally when we are apart andleave messages for later. We can also leave written messages for later. We can formimages using cameras to be stored or transmitted.

With the development of logarithms and calculators, codification of language went evenfurther, allowing the development of computers, originally called ’difference engines’,cell phones, mp3 players and many other gadgets that we now take for granted.

Mathematical notation: Further reading

Go online

Go to http://www.macs.hw.ac.uk/~greg/calculators/napier/great.html and http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Babbage.html to read about thecontributions of John Napier and Charles Babbage to this revolution.

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Verbal communication: Further reading

Go online10 min

You may wish to compare communication among chimpanzees with communication byhumans which you can do so by investiagating the following website: http://www.janegoodall.org/chimp_central/chimpanzees/behavior/communication.asp


http://www.macs.hw.ac.uk/~greg/calculators/napier/great.html

http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Babbage.html

http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Babbage.html

http://www.janegoodall.org/chimp_central/chimpanzees/behavior/communication.asp

http://www.janegoodall.org/chimp_central/chimpanzees/behavior/communication.asp


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5.7 Learning points

Summary

Forms of infant attachment

• Early infant attachment is important in laying the foundation for the futureformation of stable relationships.

• Attachment becomes evident between six and nine months after birth.

• Explain the ’strange situation’ procedure.

• Describe the responses to the ’strange situation’ procedure as: secure andinsecure attachment, detachment, anger, and inconsistent responses.

• Infants who form secure attachments are more likely to investigate theirimmediate environment, which helps the development of their cognitiveabilities.

Long period of dependency

• Humans have a relatively long period when they are dependent on adults.

• The long period of dependency provides opportunities for socialisation andlearning.

• Different methods of control during a child’s development can influencesocial competence.

• Authoritative control (providing direction) generally results in greater socialcompetence than authoritarian or permissive control.

Non-verbal communication

• Non-verbal communication contributes to the formation of relationshipsbetween individuals.

• Non-verbal communication can signal attitudes and emotions.

• Non-verbal communication acts as an aid to verbal communication.

Verbal communication

• Language uses symbols to represent information.

• Language enables information to be organised into categories andhierarchies.

• This organisation of information accelerates learning and intellectualdevelopment.

• The ability of humans to communicate verbally has resulted in thetransmission of knowledge, development of culture and social evolution.





You should have a good understanding of human communication before attempting thequestion.


Extended response question: Human communication

15 min

Describe ways in which humans communicate under the headings:

A) non-verbal communication; (4 marks)

B) verbal communication. (6 marks)

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End of Topic 5 test

Go online


Early infant attachment is important for investigate theirenvironment.

Attachment becomes evident betweendifferent methods ofcontrol.

Two responses to the strange situation experiment are dependent on adults.

Infants who form secure attachments are more likelyto

greater socialcompetence.

Humans have a relatively long period when they are six and nine months afterbirth.

The long period of dependency provides opportunitiesfor

detachment and anger.

Social competence can be influenced by future stable relationships.

Authoritative control generally results in socialisation and learning.



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Non-verbal communication contributes to the �� of relationships betweenindividuals. It can signal �� and emotions, and acts as an �� to verbalcommunication.

Language uses �� to represent �� and enables information to beorganised into �� and hierarchies. This organisation of information accelerates�� and �� development. The ability of humans to communicate verballyhas resulted in the transmission of ��, development of ��, and socialevolution.

Word list : aid, attitudes, categories, culture, formation, information, intellectual,knowledge, learning, symbols.

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The following four questions refer to infant attachment the ’strange situation’ procedure.

Q8: Which people would be involved in the procedure other than an infant and aparent/carer? (2 marks)

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Q9: Which observation is most significant in deciding the category to which the infantbelongs? (1 mark)

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Q10: Which group of infants are not distressed by the parent/carer’s absence? (1 mark)

a) Securely attachedb) Insecurely attached, avoidantc) Insecurely attached, resistantd) Disorganised attachment

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Q11: Which type of response is most likely to develop the infant’s cognitive abilities? (1mark)

a) Securely attachedb) Insecurely attached, avoidantc) Insecurely attached, resistantd) Disorganised attachment

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Q12: When does infant attachment first become evident? (1 mark)

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Q13: State two aspects of an infant’s development for which the human’s long period ofdependency provides opportunities. (1 mark)

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Q14: Which type of parental control results in the greatest social competence? (1 mark)

a) Authoritativeb) Authoritarianc) Neglectfuld) Permissive

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Q15: What are the characteristics of neglectful parenting? (2 marks)

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Q16: What can be signalled by non-verbal communication? (1 mark)

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Q17: How does language represent information? (1 mark)

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Q18: Into what does language enable information to be organised? (1 mark)

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Q19: List two advantages of this organisation of information. (1 mark)

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Q20: State two key characteristics of humans that are facilitated by language. (2 marks)

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131

Topic 6

The effect of experience and socialinfluences

Contents

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

6.2 The effect of practice on motor skills . . . . . . . . . . . . . . . . . . . . . . . 132

6.3 Imitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

6.3.1 Monkey see, monkey do! . . . . . . . . . . . . . . . . . . . . . . . . . . 134

6.4 Trial and error learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

6.5 Generalisation and discrimination . . . . . . . . . . . . . . . . . . . . . . . . . 137

6.6 Social facilitation and deindividuation . . . . . . . . . . . . . . . . . . . . . . . 139

6.7 Influences that change beliefs . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

6.8 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142


6.10 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Learning objectives


• define the term ’learning’;

• explain why practice improves motor skills;

• describe the role of imitation in learning;

• explain how learning can be improved by means of reinforcement, shaping,extinction, and trial and error;

• describe the processes of generalisation and discrimination.

132 TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES

6.1 Introduction

Like nearly all Primates, humans are social animals, i.e. they live in groups ratherthan on their own. These groups consist of closely related individuals belonging toseveral generations. The social changes brought about by industrial and agriculturaldevelopment have disrupted these groups, but it is only a few generations ago that theywere the units around which our society was structured, e.g. the clans of the Highlandsand the Borders.

In such a social structure, the children live throughout their dependent years in closeproximity to adults at home and at work, and this provides abundant opportunities toobserve and copy behaviour, and to experiment within the sheltered confines of thegroup. Furthermore, it allows the adults to supervise the young, applauding goodbehaviour and discouraging bad. By the time a person has reached the status ofadult, they will have been thoroughly versed in the ways of their tribe and their localenvironment, and in the skills necessary to survive in both. Principal among these skillsis the ability to learn, i.e. to change behaviour in the light of experience.

6.2 The effect of practice on motor skills�

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Learning objective


• state that learning is a change in behaviour brought about by experience;

• explain that motor skills are improved by repeated practice;

• state that practice of a motor skill establishes a motor pathway in the brain.

Learning can be defined simply as a change in behaviour as a result of experience. Inother words, if you start climbing a set of stairs on a different side to normal as a resultof standing on a squeaky floor-board, you have learned. Changing behaviour underliesall teaching and learning.

Motor skills are sequences of movements that are necessary to perform a particulartask. An apparently simple action, such as picking up a pencil, belies the complexityof the neural activity which enables it to be carried out smoothly and without consciousthought. There is the sensory input that is required to recognise the pencil amongst itssurroundings, and to judge its position relative to the hand. Then there is the activity ofthe motor cortex of the brain to initiate the necessary muscular contractions to move thearms and fingers, and the action of the cerebellum to co-ordinate the contractions andrelaxations of these muscles to give the fine motor control involved in precisely closingthe fingers around the pencil. Easy, but definitely not simple!

Learning motor skills from a book is very ineffective. Even with diagrams and pictures,it is still very hard to make the right movements. On the other hand, observing some-one else perform the task and then copying them works very well. Although we usuallydon’t get things right straight away, repeated demonstration quickly corrects mistakes.This establishes the movements that must be produced, but to be able to reproduce


TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 133

them reliably requires the establishment of a motor pathway linking all the parts of thenervous system, which must work together to make the movement possible. That canonly be done by repetition.

This is why professional golfers spend hundreds of hours working on a new swing,or professional tennis players practice serve after serve for hours on end. They are’grooving in’ the movements so that they automatically perform them correctly in a matchsituation. Indeed, if things go wrong and they have to start thinking about it, their gamecan fall apart.

These principles apply to mere mortals as well. If you want to play guitar better, or casta fishing fly more accurately, there is only one route to success - practice, practice,practice... It is said that to learn a folk tune, you have to play it faultlessly eightytimes, and that to become competent on an instrument takes 10,000 hours of practice.Fortunately, correctly managed, the learning process itself can be enjoyable, and thesense of achievement as progress is made is a reward in itself.

The effect of practice on motor skills: Questions

Go online

Q1: What is meant by the term ’learning’?

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Q2: What must be established to learn a motor skill?

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Q3: What is meant by practising a motor skill?

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6.3 Imitation�

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Learning objective


• explain that a great deal of human behaviour is learned by observing andimitating the behaviour of others.

As mentioned in the previous section, imitation is a very effective method of learningcertain types of skill. The apparent simplicity of the activity once more masks theconsiderable underlying complexity of the actions that take place in the nervous system.Once the other person’s actions are observed (seen or heard), somehow the brainco-ordinates the activity of the appropriate muscles to produce the same activity.The underlying neurological processes seem to be very complex and, as yet, littleunderstood, although certain cells in the motor cortex may be involved which are knownas mirror neurons. These fire impulses when an activity is the same as that observed inanother person.



However it may come about, imitation is the mechanism by which a great deal ofbasic human behaviour is learned, whether it be how to use a knife and fork, or howto behave towards our children. The importance of parents as role models for theirchildren is obvious and well-known. Much of this, such as gender stereotyping, iswholly unconscious learning, and only becomes apparent in our actions and responsesto particular situations.

6.3.1 Monkey see, monkey do!

Researchers have recently demonstrated that monkeys ’imitate with a purpose’, copyingbehaviour as a form of social learning. Such mimicry had previously been establishedonly in great apes, including humans and chimps, but now Italian researchers haverecorded the phenomenon in newborn rhesus macaques.

Most of us have delighted in very young relatives mimicking our facial expressions.This ’imitation period’ lasts up to three months in human infants. Newborns rely onwatching adults to learn facial expressions, and mimicry is thought to be crucial in thesuccessful development of parent-infant relationships.

It is thought that specific brain cells, called ’mirror neurons’, fire in a human infant whenit watches an adult expression and copies it. Similar mirror neurons are active duringbrain scans when rhesus monkeys watch another animal perform an action, and alsowhen they copy that action. This similarity suggests a common brain pathway inhumans and monkeys.

A newborn macaque (less than 10 days old) imitates tongue protrusion by a human(Evolution of Neonatal Imitation. Gross L, PLoS Biology Vol. 4/9/2006, e311 http:/ / dx.

doi.org/ 10.1371/ journal.pbio.0040311)

Pier Ferrari at the University of Parma, Italy, and colleagues, tested 21 newbornmacaques by holding each in front of a researcher who made various facialexpressions as illustrated above.


http://dx.doi.org/10.1371/journal.pbio.0040311

http://dx.doi.org/10.1371/journal.pbio.0040311


None of the infants showed any imitation at one day old. By day three, infants started tocopy the researchers’ expressions, including sticking their tongues out, opening theirmouths on cue, and smacking their lips. These are all expressions that are typical ofnormal macaque behaviour. Watch footage of macaques copying tongue poking andmouth opening in the video at the end of this topic.

Although it is possible that macaques may copy other macaques for longer in the wild,imitation of researchers had ceased by the age of two weeks. It seems that thecapacity for imitation evolved earlier in primate evolution than previously thought, anddefinitely before the rhesus monkey ancestor split from the human line of descent,about 25 million years ago.

6.4 Trial and error learning�

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Learning objective


• explain that behaviour patterns which have positive consequences for theindividual are likely to be repeated;

• state that positive outcomes reinforce a behaviour;

• state that behaviours which are not rewarded by positive outcomes, or havenegative outcomes, will disappear;

• state that a behaviour which is extinguished is said to be extinct;

• explain shaping as rewarding behaviour that successively approximates to thedesired behaviour.

Trial and error

Even more than other mammals, humans are inquisitive creatures. They are constantlyexploring, whether it be new continents or new foods, and they are always askingquestions of their environment. Equally, especially in our youth, we are prone tochallenge the ways in which things are done and to try alternatives. This behaviouris what has brought us from the Stone Age to the Computer Age within the span of onlysome 400 generations in Britain.

How many of us start pressing buttons without consulting the manual when taking a newelectronic gadget out of its packaging? In doing this, we are using one of the simplestof our learning techniques, called Trial and Error. We try something to see whether itworks; if it has a desired outcome, that reinforces the behaviour and we are likely torepeat it. If it has no effect, or worse still, results in an undesirable outcome, then thebehaviour of pressing that button will not be repeated; it will become extinct.



Reinforcement

The process of training and teaching seeks to reinforce positive outcomes andextinguish negative ones. Rewarding desirable behaviour is a very effective methodof reinforcing it. When a puppy lies down on command, you show your pleasure by yourtone of voice and the treat that you give it. This is a reward for the puppy, and it is morelikely to repeat the behaviour when the command is given again. Alternatively, jumpingup with muddy paws to greet people is a behaviour of a puppy that we would want toextinguish. This can either be done by ignoring it, or by showing displeasure in yourtone of voice.

Providing a reward is positive reinforcement, whereas something removed or avoidedacts as negative reinforcement. A good example of negative reinforcement is putting upan umbrella when the rain starts. This is classed as negative in that it is the removal ofthe stimulus of the rain on the head which reinforces the behaviour. Another examplewould be donning earphones when the next-door neighbour starts playing his banjo.

Negative reinforcement is frequently confused with punishment. Whereas showingdisapproval often works very effectively towards extinguishing a behaviour, e.g. theword "No!" exclaimed very firmly, physical punishment usually has outcomes which arenot intended. A puppy that is struck learns to fear the person who hits it rather than tokeep its paws on the floor.

It is also worth pointing out that the reward, or indeed the punishment, must havemeaning for the subject. You are unlikely to reinforce desired behaviour in a youngchild by offering her dark chocolate, or depriving her of the chance to watch the newson the television.

Shaping

Shaping is rather more than the rewarding of behaviour that approximates to thatdesired. More correctly, it is the differential reinforcement of successive approximationsto a desired behaviour. It was first identified by the American psychologist andbehaviourist B. F. Skinner who initially worked with pigeons, even developing a pigeon-guided missile for the US navy in World War II. His later analyses of teaching andlearning processes were, and still are, enormously influential.

Although its definition sounds very complex, shaping is, in fact, very simple and usedall the time in training and teaching situations. Anyone who has had to endure theinitial stages of a relative learning to play a musical instrument will be familiar with thescreeches and wails of their early efforts. Yet, these same excruciating sounds will elicithigh praise from the teacher, for the pupil has actually managed to make a sound withthe instrument. Soon though, only more melodious efforts will lead to praise. Thus,the instructor keeps raising the bar for the pupil, demanding more achievement eachtime before the reward of praise is forthcoming. Think of your own efforts at learning topronounce words in a foreign language and how they were dealt with by your teacher.



Trial and error learning: Question

Go online


Trial and error becomes extinguished.

Extinct behaviourinvolves differential reinforcement of successiveapproximations to a desired behaviour.

Reinforcement involves random responses to a stimulus.

Shapinginvolves making similar response to a stimulus morelikely on subsequent occasions.

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6.5 Generalisation and discrimination�

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Learning objective


• explain that generalisation is the process by which a response learned to inreaction to one stimulus is evoked by a different, but similar, stimulus;

• explain that discrimination is the process by which people learn to make differentresponses to different, but similar, stimuli.

Generalisation and discrimination are vital parts of our learning skills in that they allowus to develop fundamental responses to aspects of our environment.

Generalisation

How often do you hear someone declaring that they don’t like fish or green vegetables,probably as a result of an encounter with a particularly poorly cooked example early inlife? While these are trivial examples (although not to the anguished grandparent whosees a carefully prepared meal refused), learning to avoid snakes or stripy flying insectsare not. Generalisation involves identifying some key, common feature of objects whichallows us to group them together despite their being different in other respects.

The classic example is the child who generalises the response to being bitten by a dogonce to a fear of all dogs. In practice, the opposite situation is more dangerous: a childwho is accustomed to running up to pat a friendly dog is in much more danger if shegeneralises this to assume that all the dogs she meets will be friendly.



Discrimination

The process of discrimination involves the identification of key features of an objectthat will allow us to distinguish it from other similar objects.

Chanterelles are very tasty golden-yellow fungi which grow quite widely in Scottishwoods. Unfortunately, there are some seriously poisonous species with which they canbe confused. It is essential to know the precise characteristics which differentiate it fromother yellow fungi found on the forest floor if a truly mouth-watering omelette is to beconfidently enjoyed.

Many tourists visiting the Highlands go home happy that they have spotted GoldenEagles soaring over the glens, when in fact they have seen the similar, but far morecommon, buzzard. As with the Chanterelle, once the real thing has been seen, it isunlikely that there will be further confusion because the key features of the organism arerecognised.

Again, the classic example involves dogs. A postman who has been given a little nip bya Jack Russell terrier will be very wary of this breed even though he may cheerily greetmuch larger dogs such as Labradors.

Generalisation and discrimination: Question

Go onlineQ5: Complete the table by placing the activities in the correct column.

Generalisation Discrimination

Activities:

• Catching the No. 54 bus at the bus station

• Checking the tomatoes in the supermarket before putting them in the bag.

• Enjoying travelling by train.

• Midges spoil camping holidays in Britain.

• Not liking the people from a particular city.

• Only eating the sweets in the purple wrappers.

• Picking the spotted puppy from the litter.

• Randomly choosing any dish on the menu.

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6.6 Social facilitation and deindividuation�

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Learning objective


• explain that the performance of a task may be improved in the presence ofothers;

• state that the presence of others in a competitive situation may enhanceperformance;

• state that the presence of an audience may improve performance;

• state that deindividuation is responsible for the loss of identity in a crowd;

• explain that deindividuation leads to diminished restraints on behaviour;

• state that deindividuation leads to behaviour which would not be shown byindividuals on their own.

This topic considers the positive and, sometimes, negative effects that the presence ofother people can have.

Social facilitation

The presence of other people can have a marked effect on our performance of a task.This is known as social facilitation. Sometimes, this effect can have a positive influence,e.g. when playing a team sport, most of us will endeavour to improve our performancefor the good of the team.

This is called the co-actor effect: increased performance in competitive situations. Whena group of cyclists were timed on their own, against the clock, they did much worse thanwhen cycling in groups. This effect is present even in situations which would not normallybe seen as competitive. For example, car drivers take 15% longer to travel the first 100metres after drawing away from a green light if there is no other car in the next lane.

A second kind of social facilitation operates when performing in front of an audience:the audience effect. When people talk about a home advantage in sporting events, it isthe effect of the home crowd inspiring their team that is involved. If a team is required toplay a fixture in an empty stadium, it very seldom results in an entertaining game. In the2012 London Olympics, many of the British medal winners cited the crowds as a majorcontributor to their success.

On the other hand, some research has shown, and you may empathise with this, thatthe presence of others can impair performance. This gives a clue as to how socialfacilitation can operate. A certain level of arousal of the nervous system will lead toimproved performance. After this, further arousal will cause distress.

Arousal seems to help when we feel in control of a situation. When performing a taskwhich is well within our capabilities, social pressure improves performance, but, whenthe task is unfamiliar, we perform below par. In one study, expert pool players who potted71% of their shots when practising alone made 80% of the shots with an audience offour people. As you would expect, poor players who made only 36% of their shots whenunobserved, collapsed to just 25% when observed. This explains why confidence is so



important when performing. If confidence is high, social facilitation makes us do welland vice versa.

Deindividuation

Anyone who has attended a big club football match will be aware that the behaviourof some of the crowd can be quite surprising if you are not used to it. The chanting,swearing, and gesturing towards opposition players and supporters, and of course thereferee, would quickly lead to a person being arrested if it was to be repeated in thelocal High Street. And yet, these same people, when dispersed from the stadium, donot behave in this way - it is, in fact, quite atypical of them. Also, it is more than justbelieving that in a mob you are less likely to be caught and that, therefore, you can takegreater risks than usual.

This effect has a name: de-individuation. It is defined as the loss of personal identityin groups, leading to diminished restraints on behaviour. When we become a memberof a group, we somehow submerge our own personality into a group identity. There isdiminished restraint, and anti-social behaviour can occur. This same effect can influenceindividuals in groups outside the confines of a football stadium, where it can lead tovandalism, looting and rioting as it did in London and other English cities in the summerof 2011.

A classic experiment that demonstrates this behaviour involved giving students variousproblems, alone or in groups. If shown a line and asked to compare it with several otherlines for length, solo students performed very well. However, when invited to perform thesame task along with three or four ’plants’ who were primed to give obviously incorrectanswers, the subjects doubted themselves to the extent that they joined in with the groupbehaviour and gave answers that they clearly knew were wrong.

Similarly, in another classic experiment, students who had been invited to administerelectric shocks to other students in a room next door would keep turning up the voltagewhen instructed by their supervisor, who would urge them to continue even when theyraised objections. No shocks were actually administered, of course, although the subjectheard the wails of an actor in mock pain, which increased with the severity of the voltage’applied’. They were prepared to over-ride their own reservations about their actionswhen they were in conflict with orders from an authority figure, even though they wereaware of the apparent effect of their actions. This is known as the Milgram experiment.In fact, participation in this experiment had quite disturbing effects on the students. Itsorigin was the defence given by soldiers on trial for committing atrocities during WorldWar II that "they were only following orders".

Social facilitation and deindividuation: Question

Go onlineQ6: Match the phrases on the left with the words on the right.

Performance improved by the presence of others: deindividuation.

Performance improved in front of a crowd: co-actor effect.

Performance improved by having competition: audience effect.

Loss of identity in a crowd: social facilitation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



6.7 Influences that change beliefs�

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Learning objective


• explain that internalisation is the changing of one’s beliefs as a result ofpersuasion;

• explain that identification is the changing of one’s beliefs to those of an admiredinfluencing source.

Internalisation

We have defined behaviour as our range of responses to stimuli in our environment,and to other humans who form part of that environment. During our interactions withothers we frequently seek to change their views, and they try to change ours. Ourusual approach is to attempt to persuade our audience to share our view by presentingthem with convincing evidence. You may, or may not, be impressed by the argumentthat "my team has won ten games this season and yours has only won five, so we aretwice as good as you", but similar versions are heard all the time.

This approach to changing beliefs is called internalisation. It is used frequently by theadvertising industry, e.g. "Nine out of ten cats interviewed said they preferred Purr-fectCat Food". A more convincing use of the technique is found in the 502 pages of evidencepresented by Charles Darwin in his seminal book "On the origin of species by means ofnatural selection".

Identification

Advertisers also utilise another approach to changing behaviour. They have workedout that humans are social animals and prefer to have group membership. Individualstry to have a high status in groups because this confers all sorts of benefits, suchas preferential access to food and mates. One way in which to gain this status is toimpress the group by being identified with famous people. Consequently, sponsors paylarge sums of money to entice iconic figures to endorse their products. Advertisementsoften feature well-known celebrity figures from sport, film or TV, associating them withproducts, e.g. after-shave or shampoo.

The rationale of this technique is that people will want to be linked to a star, purchasinga product to be like them. This is known as identification and is defined as the changingof one’s beliefs to those of an admired influencing source.

Influences that change beliefs: TV adverts

The next time that you watch a commercial TV station, try to decide which technique isbeing used by each advertisement.

Various techniques are used, sometimes at the same time, so you might like to makeup a table headed with the different approaches that you have identified, and note theproducts that are being sold under each heading.

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6.8 Learning points

Summary

The effect of practice on motor skills

• Learning is a change in behaviour brought about by experience.

• Motor skills are improved by repeated practice.

• Practice of a motor skill establishes a motor pathway in the brain.

Imitation

• A great deal of human behaviour is learned by observing and imitating thebehaviour of others.

Trial and error learning

• Behaviour patterns that have positive consequences for the individual arelikely to be repeated.

• Positive outcomes reinforce a behaviour.

• Behaviours that are not rewarded by positive outcomes, or have negativeoutcomes, will disappear.

• A behaviour that is extinguished is said to be extinct.

• Shaping is rewarding behaviour that successively approximates to thedesired behaviour.

Generalisation and discrimination

• Generalisation is the process by which a response learned in response toone stimulus is evoked by a different, but similar, stimulus.

• Discrimination is the process by which people learn to make differentresponses to different, but similar, stimuli.

Social Facilitation and deindividuation

• Performance of a task may be improved in the presence of others.

• The presence of others in a competitive situation may enhanceperformance.

• The presence of an audience may improve performance.

• Deindividuation is responsible for the loss of identity in a crowd.

• Deindividuation leads to diminished restraints on behaviour.

• Deindividuation leads to behaviour which would not be shown by individualson their own.

Influences that change beliefs

• Internalisation is the changing of one’s beliefs as a result of persuasion.

• Identification is the changing of one’s beliefs to those of an admiredinfluencing source.





You should have a good understanding of group behaviour and social influence beforeattempting the question.


Extended response question: Group behaviour and social influence

15 min

Give an account of group behaviour and social influence under the headings:

A) social facilitation; (3 marks)

B) deindividuation; (4 marks)

C) influences that change beliefs. (4 marks)

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End of Topic 6 test

Go online


A change in behaviour brought about by experience: shaping.

An important part of learning: imitation.

Improved by repeated practice: extinct.

Established by practice of a motor skill: learning.

Copying behaviour: reinforcement.

Makes behaviour patterns likely to be repeated: observing.

Rewarding desired behaviour: motor skills.

Fate of behaviour that is not rewarded: motor pathway.

Rewarding behaviour as it gets closer to what is wanted: positive outcomes.



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�� is the process by which a response learned to one stimulus is evoked bya �� but similar stimulus, whereas �� is the process by which peoplelearn to make different responses to �� stimuli.

The presence of others in a �� situation may enhance performance, as can thepresence of an �� may improve performance. These are examples of differenttypes of social ��. �� is responsible for the loss of identity in a crowdwhich may lead to diminished �� on behaviour.

�� is the changing of beliefs as a result of persuasion. �� is thechanging of one’s beliefs to those of an admired influencing source.

Word list : audience, competitive, deindividuation, different, discrimination, facilitation,generalisation, identification, internalisation, restraints, similar.

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Q9: Explain why certain behaviours are likely to be repeated and others becomeextinct. (2 marks)

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Q10: Describe the process of simple reinforcement. (1 mark)

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Q11: Describe the process of shaping. (1 mark)

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Q12: Explain why a child being bitten by a small white dog might lead to discrimination.(1 mark)

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Q13: Explain why a child being bitten by a small white dog might lead to generalisation.(1 mark)

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Q14: Suggest why athletes almost invariably achieve their best performances in bigcompetitions. (2 marks)

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Q15: Advertisers of facial creams use either celebrities or actors dressed as scientiststo try to sell the product. Explain their reasoning. (2 marks)

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145

Topic 7

End of unit test

146 TOPIC 7. END OF UNIT TEST

End of Unit 3 test

Go onlineQ1: Complete the sentences by matching the parts on the left with the parts on theright. (12 marks)

The central nervous system comprises the brain and sensory information.

The sympathetic and parasympathetic nervous systems act information.

The limbic system influences the pituitary through thesecretion of

the spinal cord.

Perception is the process by which the brain analysesincoming

severe injury.

Information is lost from Short-Term Memory by antagonistically.

Glial cells support and maintain neurons by removingdebris by attachment.

Increased endorphin production is associated with persuasion.

Recreational drugs may inhibit the enzymatic degradationof

hormones.

A trait that becomes evident between six and nine monthsafter birth is

experience.

Language uses symbols to represent phagocytosis.

Learning is a change in behaviour brought about by neurotransmitters.

Internalisation is the changing of beliefs as a result ofdisplacement ordecay.


TOPIC 7. END OF UNIT TEST 147

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In an experiment into the serial position effect, pupils in a class were shown how toanswer by watching a teacher do a similar experiment. They were then shown twelvepictures and asked to recall them.

The table below records their success at recalling each picture.

Pupil1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th

1√ √ √ √ √ √ √ √ √

2√ √ √ √ √ √ √

3√ √ √ √ √

4√ √ √ √ √ √ √ √

5√ √ √ √ √ √ √ √

Recall(%) 100 80 80 40 ? 20 40 40 60 80 100 80

Position of picture in list shown to pupils:√

= picture recalled

Q2: What is the percentage recall of the 5th picture? (1 mark)

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Q3: Express the percentage recall of the 3rd and 9th pictures as a simple whole-number ratio. (1 mark)

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Q4: Describe the trends shown in the data. (2 marks)

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Q5: Suggest two ways in which the reliability of this experiment might be improved. (1mark)

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Q6: Suggest two variables that would have to be kept constant in this experiment. (2marks)

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Q7: Predict how the results table would look if twenty pictures had been used insteadof twelve. (1 mark)

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Q8: With reference to the brain, state two functions regulated by the medulla. (2marks)

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148 TOPIC 7. END OF UNIT TEST

Q9: What is the part of the brain that is responsible for muscular co-ordination? (1mark)

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Q10: State one secretory function of the hypothalamus. (1 mark)

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Q11: State one regulatory function of the hypothalamus. (1 mark)

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Q12: Name one state that the limbic system influences. (1 mark)

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Q13: Name the neurotransmitter involved in the reward pathway. (1 mark)

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Perception is the process by which the brain analyses and makes sense of incomingsensory information.

Q14: Into what do we organise our perceptions to segregate them? (1 mark)

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Q15: State two visual clues used in the perception of distance. (2 marks)

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Q16: What feature is most important in the recognition of objects? (1 mark)

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Q17: What does language use to represent information? (1 mark)

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Q18: What term is used to describe the process by which a child who has beenscratched by a cat comes to fear all cats? (1 mark)

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Q19: What causes some-one to change their beliefs by internalisation? (1 mark)

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GLOSSARY 149

Glossary

Addiction

continued indulgence in a behaviour despite the negative consequences - may bepsychological (a habit) or physiological (a dependence)

Antagonistic

muscles which work against each other at a joint to produce controlled movement,e.g. biceps and triceps at the elbow

Autonomic nervous system

(ANS) responsible for involuntary homeostatic control of many body functions

Axon

the long, slender projection of a neuron, that typically conducts impulses in onedirection, away from the neuron’s cell body and dendrites to the axon terminals

Behaviour

the response of an organism to internal and external stimuli

Binocular disparity

our two eyes have a slightly different view of the same scene because their pupilsare about 65mm apart

Cell body

part of the neuron which contains the nucleus with its DNA and which controls theactivity of the cell

Central core

the medulla and the cerebellum

Central nervous system

(CNS) the brain, spinal cord, retina and optic nerve

Cerebellum

part of the brain which controls balance and muscular coordination

Cerebral cortex

the thin outer layer of the cerebrum, comprising three parts: the sensory, motor,and association areas

Chunking

the grouping of separate items of information so they pass into memory as a singleunit

Dendrite

part of the neuron which carries impulses towards the cell body

Desensitisation

the effect of the drug reduces with repeated exposure because there is a decreasein the number and sensitivity of receptors - the drugs involved are agonists


150 GLOSSARY

Discrimination

identifying key features of an object to distinguish it from similar objects

Dopamine

neurotransmitter involved in the reward pathway of the brain, which is alsoimportant in a wide range of other brain functions including sleep, mode, attention,working memory, and learning

Double circulation

a blood circulation which passes the blood through the heart twice for everycomplete pass around the body

Effector

any organ capable of responding to a stimulus from a motor neuron, e.g. muscles,glands

Elaboration

linking new information with emotions, images and other memories

Elaborative encoding

transfer of information from STM to LTM by elaboration

Encoding

process by which information is converted into a form which can be passed fromSTM to LTM

Endocannabinoid

lipid signalling molecules which act like neurotransmitters in some ways, but arevery different in others

Endorphins

opioid peptides produced by the pituitary gland and hypothalamus which act asneurotransmitters to reduce pain and increase feelings of well-being

Figure

object differentiated from its surroundings (ground)

GABA

gamma-amino-butyric acid is an inhibitory neurotransmitter found at most fastinhibitory synapses throughout the brain

Generalisation

the process by which a response learned in reaction to one stimulus is evoked bya different, but similar, stimulus

Glial cells

cells that support and maintain neurons

Grey matter

comprises the cell bodies of neurons and unmyelinated neurons (which lack a fattymyelin sheath)


GLOSSARY 151

Ground

background sensory information against which objects (figures) are discerned

Hippocampus

part of the limbic system, located in the lower central region of the cerebrum,which is important in moving information from short- to long-term memory andspatial navigation

Hypothalamus

a small portion of the brain lying in the centre at the base of the cerebrum; partof the limbic system which links the nervous system to the endocrine systemthrough the pituitary gland; also controls body temperature, hunger, thirst, sleepand circadian cycles through the autonomic nervous system

Identification

changing of one’s beliefs to those of an admired influencing source

Imitation

behaviour whereby an individual observes and replicates another’s

Impulse

the temporary reversal of the electrical potential difference across the plasmamembrane of the cell of a neuron which passes along the axon of a neuron

Innate

inborn

Internalisation

changing of one’s beliefs as a result of persuasion

Interneuron

a neuron which connects with other neurons (including sensory, motor or otherinterneurons) in the CNS

Limbic system

located at the base of the cerebrum, this is a system consisting of many partsof the brain, including the hypothalamus, which is concerned with the formationof memories, and influences emotional and motivational states; it also regulatesblood pressure, body temperature and water balance

Medulla

part of the brain which controls heart rate, breathing rate and blood pressure, aswell as several simple reflexes

Memory span

the number of items that can be stored in Short-Term Memory

Metabolic activity

all of the chemical reactions going on within cells


152 GLOSSARY

Mood

a psychological state which is less immediately affected by events than emotion,and less permanent than personality or temperament

Motor neuron

a neuron which connects effectors such as the muscles or glands to the centralnervous system

Motor skills

sequences of movements that are necessary to perform a particular task

Myelin

a substance made largely of lipoprotein which is wrapped around the axon ofsensory-motor neurons by a type of glial cell called a Schwann cell

Nerve

an enclosed bundle of axons in the peripheral nervous system (in the CNS theseare known as tracts)

Neuroglia

glial cells

Neuromuscular junction

the connection between the axon terminal of a motor neuron and a muscle fibre

Neuron

a cell that transmits and processes information by means of electrical and chemicalsignals; such cells are often referred to as nerve cells, which is strictly incorrectbecause nerves contain other types of cells as well as neurons, e.g. Schwanncells

Neurotransmitters

a range of chemicals which convey messages between neurons, or neurons andeffectors

Opioid

substances which attach to the opioid receptors in the central and peripheralnervous systems - endorphins are the chemicals made in the body which do this

Organisation

grouping new information with other similar items in memory

Pacemaker

also known as the sinoatrial node (SAN), a group of modified heart muscle cellswhich generate the electrical impulses that regulate the contractions of the heart;located in the upper part of the right atrium, the SAN naturally generates impulsesbetween 60 - 100 times a minute

Parasympathetic nervous system

causes decreases in heart and breathing rates, and increases in peristalsis andintestinal secretions


GLOSSARY 153

Perception

the process by which the brain analyses and interprets incoming sensoryinformation

Perceptual constancy

despite changing conditions of size, shape and colour, familiar objects areperceived in the same way

Peripheral nervous system

(PNS) all of the sensory and motor neurons outside of the central nervous systemwhich conduct impulses to and from it

Phagocytosis

absorption of materials into the cell by engulfing

Pituitary gland

an endocrine gland about the size of a pea, which, although not part of the brain,is attached to the hypothalamus at the base of the brain; secretes nine hormoneswhich regulate homeostasis

Postsynaptic

a neuron which carries receptors to bind to neurotransmitters released by thepresynaptic neuron in response to the arrival of a stimulus

Presynaptic

a neuron at which an impulse arrives first at a synapse, and which releasesneurotransmitters to signal to the postsynaptic neuron

Receptor

a specialised neuron which responds to stimulation by a particular stimulus

Recognition

identifying a perceived object as having been encountered before

Reflex

behaviour involving a reflex arc of sensory, inter and motor neurons, which is rapid,involuntary and often protective in nature

Reflexes

rapid, automatic responses to stimuli, usually involving a sensory, inter- and motorneuron reflex arc - many are protective (e.g. knee-jerk to regain balance), butothers are part of routine bodily functions (e.g. swallowing)

Reinforcement

action which makes a behaviour more likely to be repeated

Relative height

the position of an object relative to the top and the bottom of an image


154 GLOSSARY

Relative size

if two objects are of the same shape, the larger is perceived as closer

Retina

light-sensitive tissue lining of the inner surface of the eye which is considered partof the CNS, and is actually brain tissue

Retrieval

recall from LTM to the Working Memory of STM

Reward pathway

interconnected areas of the cerebral cortex and mid-brain which regulate andcontrol behaviour by inducing pleasurable effects and, when activated, reinforcebehaviours

Rods

cells in the retina which react to light of all colours, but are much more responsiveto light than the cones which can distinguish colour - by connecting to interneuronsin a convergent neural pathways, they further increase their sensitivity

Segregation

sorting sensory information by separating it into coherent objects and theirsurroundings

Sensitisation

the effect of a drug increases the more it is taken as a result of an increase in thenumber and sensitivity of neurons - the drugs involved are antagonists

Sensory neuron

a neuron which connects sense receptors to the central nervous system

Serotonin

a neurotransmitter found mainly in the gastrointestinal tract (gut), platelets andcentral nervous system (CNS) - in the CNS it regulates mood, appetite and sleep,as well as being involved in memory and learning

Shallow encoding

transfer of information from STM to LTM by rehearsal

Shaping

differential reinforcement of successive approximations to a desired behaviour

Somatic nervous system

controls the voluntary movement of skeletal muscles

Stimulus

(plural : stimuli) a change in the environment, internal or external, detected by anorganism


GLOSSARY 155

Superimposition

when objects overlap, the one which is partially obscured is perceived to be furtheraway

Sympathetic nervous system

causes increases in heart and breathing rates, and decreases in peristalsis andintestinal secretions

Synapse

the junction between the axon terminal of one neuron and the dendrite of the nextin a neural pathway

Synaptic cleft

the gap between the axon terminal of a presynaptic neuron and the dendrite of apostsynaptic neuron at a synapse

Tolerance

increasing doses of a drug are required to achieve the same effect. Resultsfrom the reduction in the number and sensitivity of receptors caused by repeatedexposure to agonist drugs

Vesicles

small lipoprotein-lined, vacuole-like structures, in the case of synaptic vesiclesabout 40nm in diameter

Visual cortex

each cerebral hemisphere has a visual cortex that is located at the back of thebrain, the one on the left processing visual information from the right eye and viceversa

Visual cue

the aspect of an image which is used to estimate relative positions of objects ortheir distance from us

Wake-sleep cycle

the daily rhythm of waking and sleeping, determined by the internal body clockand fine-tuned to environmental cues

White matter

largely composed of myelinated axons


156 ANSWERS: TOPIC 1

Answers to questions and activities

1 The structure of the nervous system

Introduction to the structure of the nervous system: Questions (page 3)

Q1: a) the central nervous system

Q2: b) muscles and glands

Q3: a) the central nervous system

Q4: b) motor neurons

Q5: a) interneurons

Divisions of the nervous system: Question (page 5)

Q6:

Autonomic nervous system: Question (page 10)

Q7:

Sympathetic Parasympathetic

Heart rate Increased Decreased

Stroke volume Increased Decreased

Breathing rate Increased Decreased

Depth of breathing Increased Decreased

Contractions of smoothmuscle of gut wall Decreased Increased

Intestinal secretions Decreased Increased


ANSWERS: TOPIC 1 157

Parts of the brain: Question (page 11)

Q8:

The central core: Question (page 12)

Q9:

Medulla Cerebellum

arousal balance

breathing movement

heart rate muscular coordination

sleep posture



Limbic system and cerebral cortex: Question (page 20)

Q10:

Process Area

Controls voluntary movement motor area

Processes information for the formationof memories

limbic system

Transfers information betweenhemispheres

corpus callosum

Influences the secretions of the pituitary hypothalamus

Recalls memories cerebral cortex

Deals with language and imagination association area

Receives impulses from the skin somatosensory area

Centre of conscious thought cerebral cortex

Controls the left side of the body right cerebral hemisphere

Acts as an integrated whole brain

Extended response question: Nervous system (page 23)

Suggested marking scheme

Each line represents a point worth one mark. The concept may be expressed in otherwords. Words which are bracketed are not essential. Alternative answers are separatedby a solidus (/); if both such answers are given, only a single mark is allocated. Inchecking the answer, the number of the point being allocated a mark should be writtenon the answer paper. A maximum of ten marks can be gained.

A) Divisions of the nervous system(maximum of 5 marks):

1. The nervous system is divided into the central nervous system and theperipheral nervous system.

2. The central nervous system consists of the brain and spinal cord.

3. The peripheral nervous system comprises all the sensory and motor neuronswhich connect it to the rest of the body.

4. The peripheral nervous system is sub-divided into the somatic and theautonomic nervous systems.

5. The somatic nervous system controls the voluntary activity of the skeletalmuscles (and thus all movement) via its sensory and motor neurons.

6. The autonomic nervous system is further divided into the sympathetic andthe parasympathetic nervous systems, which act antagonistically.



B) Homeostatic control (maximum of 5 marks):

i. The autonomic nervous system plays an important part in many involuntaryhomeostatic processes. . .

ii. . . .by conducting impulses through its sensory and motor neurons to thesmooth muscle of artery walls, the cardiac muscle of the heart, and to glands.

iii. The sympathetic nervous system prepares the body for action, ’fight orflight’. . .

iv. . . .by speeding up heart and breathing rates, and slowing down peristalsisand intestinal secretions.

v. The parasympathetic nervous system calms the body down, ’rest anddigest’. . .

vi. . . .by slowing down the heart and breathing rates, and increasing peristalsisand intestinal secretions.

End of Topic 1 test (page 24)

Q11:

Types of neuron: sensory, motor,interneuron.

Connect sense receptors to CNS: sensory neurons.

Connect CNS to muscles and glands: motor neurons.

Connect to other neurons of all types: interneurons.

Analysis of information: central nervous system.

Muscular contractions and glandular secretions: motor responses.

Divisions of the nervous system: central and peripheral.

Central nervous system comprises: brain and spinal cord.

Divisions of the peripheral nervous system: somatic and autonomic.

Sympathetic and parasympathetic:autonomic nervoussystem.



Q12:

Controls the movement of skeletal muscles: somatic nervous system.

Skeletal muscle control by sensory and motorneurons is:

voluntary.

Responsible for involuntary homeostatic control:autonomic nervoussystem.

Involuntary homeostatic control involves: sensory and motorneurons.

Motor neurons of the autonomic nervous systemconnect to:

smooth and cardiacmuscle.

Action of the sympathetic and parasympatheticnervous system:

antagonistic.

Increases heart rate, decreases intestinal secretions:sympathetic nervoussystem.

Decreases breathing rate, increases peristalsis:parasympathetic nervoussystem.

Q13: Cerebrum

Q14: Cerebellum

Q15: Central nervous system

Q16: To pass information between the cerebral hemispheres.

Q17:

Q18: Any two from:

• arousal;• breathing;• heart rate;• sleep.



Q19: Cerebellum

Q20: Central

Q21: Peripheral

Q22: Brain

Q23: Somatic

Q24: Sympathetic

Q25: Sensory and motor neurons.

Q26: Any two from:

• cardiac muscle;

• glands;

• smooth muscle.

Q27: Decrease

Q28: Increase

Q29: Limbic system

Q30: Hormones

Q31: Any two from:

• blood pressure;

• body temperature;

• water balance

Q32: Cerebral cortex

Q33: Sensory and motor

Q34: Any three from:

• imagination;

• intelligence;

• language;

• personality;

• thought.

(any one or two correct for 1 mark, any three correct for 2 marks)



2 Perception and memory

Segregation of objects: Questions (page 33)

Q1: To prevent the shape of the object being recognised against its background as itsedges are no longer clear.

Q2: They enable the organisation of stimuli into coherent patterns.

Perception of distance: Question (page 37)

Q3:

• Relative size - the human figures, parasols and the paving setts are smaller towardsthe front of the building.

• Superimposition - the sign in the foreground partly conceals the people behind it;the parasols in the mid-ground partly conceal those closer to the building.

• Relative height in the field - the sign at the foot of the photo appears much closerthan the tables higher in the image.

Location of Sensory Memory: Question (page 42)

Q4:

Serial position effect 2 (page 44)

Q5: The first few items are recalled from Long-Term Memory, possibly usingmnemonics. The middle few items are often not recalled at all. The last few itemsare still in Short-Term Memory.

Q6: Seven items are usually held in the Short-Term Memory.



Q7: If it is a particularly unusual item or a favourite item of the subject.

Short-Term Memory: Questions (page 45)

Q8:

Memory span of STM is: 7 (5-9) items.

Items remain in STM for: 15-30 seconds.

Items are maintained in STM by: rehearsal.

Items are lost from STM by: displacement and decay.

STM memory span can be increased by: chunking.

Working Memory is an extension of: STM.

Working Memory is used to perform: cognitive tasks.

Q9:

i. The early numbers have been rehearsed by repetition.

ii. The later numbers are still in STM.

iii. The middle numbers have been displaced from STM.

Long-Term Memory: Question (page 47)

Q10:

Process by which information is converted to a formwhich can stored in memory:

encoding.

Transfer from STM to LTM by repetition: rehearsal.

Transfer from STM to LTM by grouping with similaritems:

organisation.

Transfer from STM to LTM by linking with existingmemories:

elaboration.

Encoding produced by repetition: shallow.

Encoding produced by linking with emotions: elaborative.

Recall from LTM to STM: retrieval.

Clues which aid recall: contextual.



Location of memory in the brain: Questions (page 49)

Q11:

Type of memory Information stored

Episodic Events and experiences

Semantic Facts and concepts

Procedural Motor and cognitive skills

Emotional Emotional responses

Spatial Location of physical objects in space

Q12:

Events and experiences; Factsand concepts:

area of cerebral cortex where sensoryinformation first encoded.

Motor and cognitive skills: located in the motor cortex.

Emotional responses:located in the amygdala of the cortex and thelimbic system.

Location of physical objects inspace:

located in the hippocampus of the limbicsystem.

Extended response question: Short-Term Memory (page 54)



A) Increasing memory span (maximum of 3 marks):

1. Memory span is the number of items that can be retained in STM.

2. The normal short-term memory span is 7± 2 items.

3. Information is retained in STM for 15-30s.

4. ’Chunking’ of memory helps short-term memory in particular as several itemsare grouped as one.

B) Serial position effect (maximum of 5 marks):

i. A large number of items is shown briefly to the subjects so that they cannotall be retained in short-term memory.



ii. Items recalled by the subjects are recorded.

iii. Subjects usually recall items presented early and late in the series.

iv. Items at the end of the series are still retained in STM (the recency effect).

v. Items from the start of the series have been transferred to long-term memory(the primacy effect).

vi. Items from the middle of the list have been displaced from STM. . .

vii. . . .and have not been transferred to LTM.

C) Transfer from STM to LTM (maximum of 2 marks):

I. Rehearsal - repetition of information.

II. Elaboration of meaning by linking to other memories/emotions.

III. Organisation - linking to other similar memories.


Q13:

In the field, distance is judged by visual cues such as relative size, superimposition,and relative height.

Relative size refers to the apparent dimensions of similar objects, overlap of objectsis used in superimposition, and relative height refers to position in the image.

At close range, binocular disparity is also used. This uses the fact that each eye has adifferent viewpoint.

We perceive familiar objects in the same way despite changing circumstances, such asviewing angle, because of perceptual constancy.

Q14:

Conversion of information into a form that can be passed into LTM: encoding.

Repetition of information: rehearsal.

Grouping of items of information which are similar: organisation.

Linking information with emotions and images: elaboration.

Type of encoding produced by repetition: shallow.

Forms more permanent memories than shallow encoding:organisationandelaboration.

Recall from LTM to Working Memory: retrieval.

Cues which relate to the conditions under which a memory wasformed:

contextual.



Q15:

Memory of events and experiences: episodic.

Memory of facts and concepts: semantic.

Memory of motor and cognitive skills: procedural.

Memory of how we felt about past events: emotional.

Memory of the location of objects: spatial.

Part of the brain where all memory is located: cerebrum.

Where memories of events and facts are stored:sensory regions ofcortex.

Where skill-related memories are linked to long-termchanges: motor cortex.

Our feelings about past events involve links between:cortex and limbicsystem.

Part of the limbic system: hippocampus.

Q16: perception

Q17: figures

Q18: ground

Q19: coherent

Q20: segregation

Q21: b) shape

Q22: c) recognition

Q23: c) inference

Q24: c) inference

Q25: The process of storage, retention and retrieval of information.

Q26: Sensory

Q27: Sensory

Q28: memory span

Q29: rehearsal

Q30: displacement

Q31: decay



Q32: chunking

Q33: Working Memory

Q34:

Average number of items held: memory span.

Maintains items in STM: rehearsal.

New information causes loss: displacement.

Without repetition, items are lost: decay.

Improves STM: chunking.

Performs cognitive tasks involving information in STM: working memory.



3 Neurons, neurotransmitters and neural pathways

Structure of neurons: Question (page 64)

Q1:



Neurons: Question (page 68)

Q2:

Neurons: type of nerve cell.

Neurons receive and transmit: impulses.

Neurons comprise: cell body, axon and dendrites.

DNA in the cell body codes for: all cell proteins.

Carry impulses towards the cellbody: dendrites.

Axon terminals and dendrites form: synapses.

The gap between an axon terminaland a dendrite:

synaptic cleft.

Junction between an axon and amuscle fibre:

neuromuscular.

Glial cells: Question (page 70)

Q3:

The nervous system contains more than neurons. About 15% of the cells in thecerebrum are glial cells which support and maintain the neurons in several ways.Some of them monitor the conditions surrounding the neurons and maintain a constantenvironment by homeostasis. Others help repair damage by removing cell debris byphagocytosis.

Another cell of this type, called the Schwann cell, wraps lipoprotein membrane aroundaxons forming the myelin sheath, the effect of which is to greatly accelerate theconduction of impulses. Starting well before birth, this process, known as myelination,continues until adolescence. This explains why an infant’s responses to stimuli are lesscoordinated than an adult’s.

Myelination: Question (page 71)

Q4: 0.08

Neurotransmitters: Questions (page 74)

Q5: To ensure that they do not act on cell contents and to conserve resources.

Q6: Mitochondria: supply energy for active uptake of noradrenaline after its use andto provide energy for cellular functions.Ribosomes: synthesise proteins essential to produce neurotransmitters.



Neural pathways: Questions (page 81)

Q7: a) converging

Q8: b) diverging

Q9: c) reverberating

Q10: a) converging

Q11: b) diverging

Q12: c) reverberating

Q13: b) plasticity

Q14: a) brain damage

Extended response question: Sensory and motor neurons (page 85)



1. Sensory neurons pass messages from sense organs to the central nervoussystem whereas motor neurons transfer messages from the CNS to muscles andglands.

2. Both neurons consist of cell body, axon and dendrites.

3. The cell body is found part way along the axon of a sensory neuron, whereas theaxon grows out from one side of the cell body in the motor neuron.

4. In each case, the axon is wrapped in a myelin sheath with nodes every fewmillimetres.

5. At a synapse, neurotransmitters cross from the pre-synaptic neuron to the post-synaptic neuron.

6. Neurotransmitters include acetylcholine and noradrenaline.

7. The type of receptor on the post-synaptic dendrite, to which the transmitterchemical binds, determines whether the next neuron is inhibited or excited.

8. Acetylcholine is immediately degraded by an enzyme.

9. Noradrenaline is reabsorbed by active uptake.

10. Synapses filter out single weak impulses, but can sum several weak impulses.




Q15:

Cells that make up the nervous system: neurons.

Transmitted through the nervous system: impulses.

Neurons that carry information into the CNS: sensory.

Neurons that connect neurons: interneurons.

Neurons that connect the CNS to glands: motor neurons.

Carry impulses towards the cell body: dendrites.

Found at the end of the axon: axon terminals.

Increases speed of conduction of impulses: myelin.

Cells which produce the myelin sheath: glial.

Results from destruction of the myelin sheath: multiple sclerosis.

Q16:

Neurotransmitters are chemicals which relay signals between neurons in the CNSand between neurons and glands. The junction between neurons is called asynapse and that between neurons and muscle fibres is a neuromuscular junction.Neurotransmitters are secreted by exocytosis into synaptic cleft, and diffuse acrossthe gap and bind to receptors on the dendrites of the next neuron.

Signals may be excitatory or inhibitory, depending only on the receptor on thereceiving dendrite and not on the type of neurotransmitter. Neurotransmitters must beimmediately removed to prevent continuous stimulation of the post-synaptic neurons.Neurotransmitters are either removed by enzyme action (e.g. acetylcholine) or by re-uptake (e.g. noradrenalin).

Synapses can filter out weak impulses arising from insufficient secretion ofneurotransmitter.

If sufficient neurotransmitters attach to the receptors, a threshold is reached and animpulse is triggered. By summation a series of weak stimuli can combine to reach thefiring threshold in the post-synaptic neuron.



Q17:

Several neurons pass messages on to a single neuron: converging pathway.

An example of a converging pathway: rods in the retina.

Increased by a converging pathway: sensitivity to signals.

A single neuron passes messages on to several neurons: diverging pathway.

An example of a diverging pathway: fine motor control.

Neurons later in the pathway synapse with earlier ones:reverberatingpathway.

An example of a reverberating pathway: wake-sleep cycle.

New responses are created by their development:new neuralpathways.

Result of the development of new neural pathways:plasticity ofresponse.

Q18: Dendrites

Q19: Axon

Q20: Axon terminals

Q21: It is found surrounding the axon, and its function is to insulate the axon and speedup neuron transmission.

Q22: Motor

Q23: Other neurons

Q24: Sensory

Q25: Synaptic cleft

Q26: Neuromuscular junction

Q27:

• Maintaining a constant environment around the neuron.

• Producing myelin sheath.

• Removing debris by phagocytosis.

Q28: Multiple sclerosis (or other suitable)Normal neuron transmission is prevented leading to loss of co-ordination.

Q29: Synaptic vesicles

Q30: The arrival of a nerve impulse.



Q31: Diffusion

Q32: Receptors

Q33: It is the process by which several weak stimuli combine. . .. . .to reach the threshold to fire/release an impulse in the post-synaptic neuron.

Q34: Converging

Q35: Rods in the retina (other answers are possible)

Q36: A single neuron passes messages on to several neurons.

Q37: Converging

Q38: Wake-sleep cycle (other answers are possible)

Q39: Plasticity of response

Q40: Any two from:

• bypass areas of brain damage;

• create new responses;

• suppress reflexes;

• suppress responses to sensory impulses.



4 Neurotransmitters, mood and behaviour

Dopamine and the reward pathway: Question (page 93)

Q1: Organisms which do not carry out key activities will not rear many offspring oreven survive.Linking an activity to the reward pathway will increase its frequency / intensity; theorganism is more likely to carry out these beneficial activities.

Endorphins: Questions (page 95)

Q2: They inhibit the triggering of impulses in the neurons linked to pain receptors.

Q3: Beneficial: after a serious accident, an injured person may still be able to helpothers or walk to find help.Detrimental: during a tight game, a footballer may damage a muscle but continue toplay, only to later discover the extent of her injury.

Q4: Both sexual orgasm and the close physical presence of a loved one increaseendorphin secretion.Increased endorphin levels lead to feelings of pleasure and euphoria.Without these feelings, it is hard to sustain a partnership.



Neurotransmitter-related disorders and their treatment: Question (page 99)

Q5:

DisorderArea of brain

affectedNeurotransmitters

involvedDrug Treatment

Alzheimer’sdisease

Cerebral cortexand mid-brain

Acetylcholine

Acetylcholinesteraseinhibitor to raiseneurotransmitterlevels by slowingdegradation

Parkinson’sdisease

Mid-brain Dopamine

L-DOPA asprecursor ofdopamine;dopamine agonists;MAO-B inhibitors toslow dopaminedegradation

Schizophrenia Reward pathway DopamineDopamineantagonists to slowuptake

Generalisedanxiety disorder

Amygdala in cortexSerotoninNorepinephrine

GABA receptoragonists,Beta-blockers

Depression Brain-stem nearmedulla

SerotoninNorepinephrineDopamine

Drugs inhibitingnorepinephrinere-uptake; MAO-Bto inhibit dopaminedegradation



Modes of action: Question (page 103)

Q6:

Mode of action Drug Neurotransmitter

Stimulating the release ofneurotransmitters

MDMA serotonin

Agonists Cannabis GABA

Antagonists Ethanol glutamate

Inhibition of re-uptake ofneurotransmitters

Cocaineserotonin,norepinephrine anddopamine

Inhibition of degradation ofneurotransmitters

Tobacco - monoamineoxidase (MAO) inhibitors

monoamine oxidase(MAO)

Drug addiction, sensitisation and tolerance: Questions (page 104)

Q7: Changes to the number and sensitivity of receptors.

Q8: An increase in the number and sensitivity of receptors.

Q9: Antagonists

Q10: Addiction

Q11: A decrease in the number and sensitivity of receptors.

Q12: Agonists

Q13: Tolerance



Extended response question: The mode of action of recreational drugs (page106)



A) Effects on the brain (maximum of 4 marks):

1. Recreational drugs mainly affect the reward circuit of the brain. . .

2. . . .by stimulating increased secretion of dopamine. . .

3. . . .which causes feelings of euphoria and relaxation. . .

4. . . .and leads quickly to addiction.

5. The changed neurochemistry leads to changes in mood / cognition /perception / behaviour. (mention of all four examples gains this mark)

B) Modes of action (maximum of 6 marks):

i. Stimulation of release of neurotransmitter, . . .

ii. . . .e.g. MDMA stimulates release of serotonin.

iii. Agonists , imitating the action of a neurotransmitter, . . .

iv. . . .e.g. cannabis binds to cannabinoid receptors and suppresses GABAsecretion.

v. Antagonists bind to receptors and prevent neurotransmitter from doing so, . . .

vi. . . .e.g. ethanol binds to GABA receptors and depresses impulse generation.

vii. Inhibiting re-uptake of neurotransmitter, . . .

viii. . . .e.g. cocaine blocks the re-uptake of serotonin / norepinephrine / dopamine.

ix. Inhibiting neurotransmitter degradation, . . .

x. . . .e.g. tobacco contains two MAO inhibitors which suppress dopaminebreakdown.




Q14:

The reward pathway involves neurons which secrete dopamine, which induces thefeeling of pleasure and so reinforces particular behaviours. The reward pathway isactivated by beneficial behaviour.

Endorphins stimulate neurons involved in reducing the intensity of pain. Increasedlevels of endorphins are connected with appetite modulation. Increased endorphinproduction is associated with the consumption of certain foods.

Many of the drugs used to treat neurotransmitter-related disorders are similar toneurotransmitters. Agonists bind to and stimulate receptors, thus mimicking theneurotransmitter. Antagonists bind to specific receptors, so blocking the action ofa neurotransmitter. Other drugs inhibit the enzymes which degrade neurotransmitters,or inhibit reuptake.

Q15:

Many recreational drugs affect neurotransmission in the reward pathway.

Changes in neurochemistry alter mood, cognition, perception andbehaviour.

Recreational drugs may stimulate the release ofneurotransmitters.

Recreational drugs may inhibit the re-uptake ofneurotransmitters.

Drugs which imitate the action of neurotransmitters are agonists.

Drugs which block the binding of neurotransmitters are antagonists.

An increase in the number and sensitivity of receptors is sensitisation.

Sensitisation results from exposure to antagonist drugs.

Sensitisation leads to addiction.

A decrease in the number and sensitivity of receptors is desensitisation.

Desensitisation results from exposure to agonist drugs.

Desensitisation leads to tolerance.



Q16: Endorphins


• certain foods;

• prolonged and continuous exercise;

• severe injury;

• stress.

Q18: Dopamine

Q19: Pleasure / euphoria

Q20: Agonists mimic the action of the neurotransmitter.Antagonists bind to the receptor and block the action of the neurotransmitter.

Q21: Inhibit enzymes that degrade neurotransmitters.Inhibit neurotransmitter re-uptake.

Q22: The reward pathway/circuit.


• behaviour;

• cognition;

• mood;

• perception.

Q24:

• Block their binding.

• Imitate their action.

• Inhibit their degradation.

• Inhibit their re-uptake.

• stimulate their release.

Q25: An increase in the number and sensitisation of receptors.

Q26: Antagonists

Q27: Addiction

Q28: A decrease in the number and sensitisation of receptors.

Q29: Agonists

Q30: Tolerance



5 Infant attachment and the effect of communication

Imprinting: Question (page 115)

Q1:

1. Parent and infant are introduced to the experimental room.

2. Parent and infant are alone. Parent does not participate while infant explores.

3. Stranger enters, converses with parent, then approaches infant. Parent leavesinconspicuously.

4. First separation episode: Stranger’s behaviour is geared to that of infant.

5. First reunion episode: Parent greets and comforts infant, then leaves again.

6. Second separation episode: Infant is alone.

7. Continuation of second separation episode: Stranger enters and gears behaviourto that of infant.

8. Second reunion episode: Parent enters, greets infant, and picks up infant; strangerleaves.

Long period of dependency: Question (page 118)

Q2:

i. Reason: learningExplanation: humans require to learn more of their behaviour than any otheranimals, e.g. language

ii. Reason: socialisationExplanation: humans have to learn how to live in complex social groups and haveto interact with others in a wide range of situations.

Parental control methods: Questions (page 119)

Q3:

Demanding Undemanding

Responsive Authoritative Permissive

Unresponsive Authoritarian Neglectful

Q4:

i. Authoritative parenting is responsive to the child’s views, involves the child indecision making, and supports the child emotionally.

ii. Authoritative parenting sets rules and standards, and expects maturity andcooperation.



Information transfer: Question (page 120)

Q5:

VerbalNon-verbal -

Body languageNon-verbal -

Gesture

Shouting outWalking with an expandedchest after a victory

Indicating that an archer’sbow finger will be cut off ifhe gets caught

TalkingFeeling your collar whenunder pressure

Pointing to your nosewhen playing charades

Sobbing loudlyShowing whites of eyeswhen angry

Throwing a fist in the air

Extended response question: Human communication (page 128)



A) Non-verbal communication (maximum of 4 marks):

1. Non-verbal communication involves gestures, signs, facial movements andposture.

2. Non-verbal communication aids verbal communication.

3. Attitudes and emotions are signalled by non-verbal communication.

4. Mirroring of non-verbal communication strengthens bonds.

5. Examples of non-verbal communication include winking, folding arms andsmiling. (three listed for one mark)

6. Any two examples explained in terms of meaning conveyed.

B) Verbal communication (maximum of 6 marks):

i. Language uses symbols to represent information

ii. Language enables information to be organised into categories andhierarchies.

iii. This organisation of information accelerates learning.

iv. Organisation of information aids intellectual development.

v. The ability of humans to communicate verbally has resulted in thetransmission of knowledge. (plus explanation)



vi. The ability of humans to communicate verbally has resulted in thedevelopment of culture. (plus explanation)

vii. The ability of humans to communicate verbally has resulted in socialevolution. (plus explanation)

viii. The ability of humans to communicate verbally has resulted in thetransmission of knowledge, development of culture and social evolution.


Q6:

Early infant attachment is important for future stable relationships.

Attachment becomes evident betweensix and nine months afterbirth.

Two responses to the strange situation experiment are detachment and anger.

Infants who form secure attachments are more likelyto

investigate theirenvironment.

Humans have a relatively long period when they are dependent on adults.

The long period of dependency provides opportunitiesfor

socialisation and learning.

Social competence can be influenced by different methods ofcontrol.

Authoritative control generally results ingreater socialcompetence.

Q7:

Non-verbal communication contributes to the formation of relationships betweenindividuals. It can signal attitudes and emotions, and acts as an aid to verbalcommunication.

Language uses symbols to represent information and enables information to beorganised into categories and hierarchies. This organisation of information accelerateslearning and intellectual development. The ability of humans to communicate verballyhas resulted in the transmission of knowledge, development of culture, and socialevolution.

Q8: A stranger and an observer.

Q9: The infant’s reunion behaviour with its parent/carer.

Q10: b) Insecurely attached, avoidant

Q11: a) Securely attached

Q12: 6-9 months



Q13: Socialisation and learning.

Q14: a) Authoritative

Q15: Any two from:

• child’s views ignored;

• no emotional support;

• standards not set.

Q16: Attitudes and emotions.

Q17: Symbols

Q18: Categories and hierarchies.

Q19: It accelerates learning and intellectual development.

Q20: Any two from:

• development of culture;

• social evolution;

• transmission of knowledge.



6 The effect of experience and social influences

The effect of practice on motor skills: Questions (page 133)

Q1: A change in behaviour as a result of experience.

Q2: Motor pathway

Q3: Repeated use

Trial and error learning: Question (page 137)

Q4:

Trial and error involves random responses to a stimulus.

Extinct behaviour becomes extinguished.

Reinforcementinvolves making similar response to a stimulus morelikely on subsequent occasions.

Shapinginvolves differential reinforcement of successiveapproximations to a desired behaviour.

Generalisation and discrimination: Question (page 138)

Q5:

Generalisation Discrimination

Not liking the people from a particular cityOnly eating the sweets in the purplewrappers

Randomly choosing any dish on themenu

Checking the tomatoes in thesupermarket before putting them in thebag

Enjoying travelling by train Picking the spotted puppy from the litter

Midges spoil camping holidays in Britain Catching the No. 54 bus at the busstation



Social facilitation and deindividuation: Question (page 140)

Q6:

Performance improved by the presence of others: social facilitation.

Performance improved in front of a crowd: audience effect.

Performance improved by having competition: co-actor effect.

Loss of identity in a crowd: deindividuation.

Extended response question: Group behaviour and social influence (page 143)


Each line represents a point worth one mark. The concept may be expressed in otherwords. Words which are bracketed are not essential. Alternative answers are separatedby a solidus (/); if both such answers are given, only a single mark is allocated. Inchecking the answer, the number of the point being allocated a mark should be writtenon the answer paper. A maximum of eleven marks can be gained.

A) Social facilitation (maximum of 3 marks):

1. Performance of a task may be improved in the presence of others.

2. The presence of others in a competitive situation may enhance performance

3. Detailed example of the point above

4. The presence of an audience may improve performance.

5. Detailed example of the point above

B) Deindividuation (maximum of 4 marks):

i. Deindividuation is responsible for the loss of identity in a crowd.

ii. Detailed example of the point above

iii. Deindividuation leads to diminished restraints on behaviour.

iv. Deindividuation leads to behaviour which would not be shown by individualson their own.

v. Detailed example of the point above

C) Influences that change beliefs (maximum of 4 marks):

I. Internalisation is the changing of one’s beliefs as a result of persuasion.

II. Detailed example of the point above

III. Identification is the changing of one’s beliefs to those of an admiredinfluencing source.

IV. Detailed example of the point above




Q7:

A change in behaviour brought about by experience: learning.

An important part of learning: observing.

Improved by repeated practice: motor skills.

Established by practice of a motor skill: motor pathway.

Copying behaviour: imitation.

Makes behaviour patterns likely to be repeated: positive outcomes.

Rewarding desired behaviour: reinforcement.

Fate of behaviour that is not rewarded: becomes extinct.

Rewarding behaviour as it gets closer to what is wanted: shaping.

Q8:

Generalisation is the process by which a response learned to one stimulus is evokedby a different but similar stimulus, whereas discrimination is the process by whichpeople learn to make different responses to similar stimuli.

The presence of others in a competitive situation may enhance performance, as canthe presence of an audience may improve performance. These are examples ofdifferent types of social facilitation. Deindividuation is responsible for the loss ofidentity in a crowd which may lead to diminished restraints on behaviour.

Internalisation is the changing of beliefs as a result of persuasion. Identification is thechanging of one’s beliefs to those of an admired influencing source.

Q9: Behaviour with positive outcomes will be repeated;behaviour with negative outcome will become extinct.

Q10: Desired behaviour is rewarded.

Q11: Behaviour which successively more closely approximates to the desired behaviouris rewarded.

Q12: The child becomes afraid of small and/or white dogs, but not others

Q13: The child becomes afraid of all dogs.

Q14: Social facilitation means that individuals perform better when competing withothers and when performing in front of an audience.

Q15: Celebrities: people may want to be like the celebrity and imitate them by using thecream.’Scientists’: people may be persuaded that they should use the product by the pseudo-science presented.



7 End of unit test

End of Unit 3 test (page 146)

Q1:

The central nervous system comprises the brain and the spinal cord.

The sympathetic and parasympathetic nervous systems act antagonistically.

The limbic system influences the pituitary through thesecretion of

hormones.

Perception is the process by which the brain analysesincoming

sensory information.

Information is lost from Short-Term Memory bydisplacement ordecay.

Glial cells support and maintain neurons by removingdebris by

phagocytosis.

Increased endorphin production is associated with severe injury.

Recreational drugs may inhibit the enzymatic degradationof

neurotransmitters.

A trait that becomes evident between six and nine monthsafter birth is

attachment.

Language uses symbols to represent information.

Learning is a change in behaviour brought about by experience.

Internalisation is the changing of beliefs as a result of persuasion.

Q2: 20 %

Q3: 4:3

Q4: Percentage recall decreases from the 1st to the 5th pictures. . .. . .then increases back up to 11th picture.

Q5:

• Increase the number of children used.

• Repeat the experiment several times.

Q6: Any two from:

• age of pupils;

• gender of pupils;

• pictures used;



• time allowed to look at the pictures;

• time delay before asking to recall the pictures after last one viewed;

• time of day when test is taken.

Q7: The first and last five pictures would be the same, the middle ten would be verylow.

Q8: Any two from:

• arousal;

• breathing;

• heart rate;

• sleep.

Q9: Cerebellum

Q10: Either of:

• influences the pituitary;

• secretes ADH.

Q11: Any one from:

• body temperature;

• controls contraction of smooth muscle;

• water balance.

Q12: Either of:

• emotional;

• motivational.

Q13: Dopamine

Q14: Figure and ground.

Q15: Any two from:

• relative height in field;

• relative size;

• superimposition.

Q16: Shape

Q17: Symbols

Q18: Generalisation

Q19: Persuasion


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