©prentice hall 20032-1 understanding psychology 6 th edition charles g. morris and albert a. maisto...

©Prentice Hall 2003 2-1

Understanding Psychology6th Edition

Charles G. Morris and Albert A. Maisto

PowerPoint Presentation byH. Lynn Bradman

Metropolitan Community College


Chapter 2

The Biological Basis of Behavior


Neurons: The Messengers

• The brain of an average human being contains as many as 100 billion nerve cells or neurons.

• Neurons vary in size and shape, but they are all specialized to receive and transmit information.



• Neurons receive messages from other neurons through short fibers, called dendrites.

• A longer fiber, called an axon, carries outgoing messages from the cell.



• A group of axons bundled together forms a nerve or tract.

• Some axons are covered with a myelin sheath, made up of glial cells; this increases neuron efficiency and provides insulation.


Three Types of Neurons

• Sensory (afferent) neurons: – Carry messages from sense organs to the

spinal cord or brain

• Interneurons (association neurons): – Carry messages from one neuron to another

• Motor (efferent) neurons: – Carry messages from the spinal cord or

brain to the muscles and glands


Glial Cells

• The nervous system also contains a vast number of glial cells or glia.

• Glial cells hold neurons in place, provide nourishment, and remove waste products.

• Glial cells prevent harmful substances from passing from the bloodstream into the brain.

• Glial cells form the myelin sheath that insulates and protects neurons.


The Neural Impulse


The Neuron At Rest

• Resting potential: the state of a neuron when not engaged in an action potential – greater positive ions outside the cell

membrane and greater negative ions inside the cell

• Polarization: inside of neuron is negatively charged relative to the outside


The Action Potential

• Neural impulse (action potential): – the firing of a nerve cell

• Graded potential: – a shift in the electrical charge in a tiny area

of a neuron

• Threshold of excitation: – the level an impulse must exceed to cause a

neuron to fire



• Neurons either fire, or they don’t.• This is called the all-or-none law.• A neuron is more likely to fire more

often when stimulated by a strong signal resulting in a rapid neural firing that communicates a message.



• Absolute refractory period: – a period after firing when a neuron will not

fire again no matter how strong the incoming message

• Relative refractory period: – a period after firing when a neuron will fire

again only if the incoming message is much stronger than usual


The Synapse


• Neurotransmitter molecules, released by synaptic vesicles, cross the tiny synaptic space (or cleft) between an axon terminal (or terminal button) of a sending neuron and a dendrite of a receiving neuron.

• Here they latch on to receptor sites, much as keys fit into locks, and pass on their excitatory or inhibitory messages.


Neurotransmitters and Their Effects

• Acetylcholine (ACh): – plays a role in arousal, attention, memory,

and motivation

• Dopamine: – plays a role in motor disorders, such as

parkinson’s disease

• Serotonin: – affects emotions, arousal, and sleep


Neurotransmitters And Their Effects

• Norepinephrine: – Influences wakefulness and arousal, as well

as learning, memory, and emotional mood

• Endorphins: – Reduce pain by inhibiting the neurons that

transmit pain messages to the brain


Drugs and Behavior

• Certain drugs produce psychological effects by increasing or decreasing the amount of neurotransmitters at synapses.

• Other drugs work on receptor sites, blocking the receptors or interfering with the removal or reabsorption of neurotransmitters.


Drugs and Behavior

• Drugs and toxins block or enhance the action of neurotransmitters– Botulism– Curare– Chlorprozamine or clozapine – Caffeine– Cocaine


Botulism

• A microorganism produces a toxin that causes botulism.

• This toxin prevents the release of ACh, which can lead to paralysis and possibly rapid death.


Curare

• Used by South American native people to tip arrows.

• Stuns or kills prey• Blocks the Ach receptors.


Chlorprozamine or Clozapine

• Trade name Thorazine• Prevents dopamine from binding to

receptor sites.• This reduction reduces schizophrenic

hallucinations.


Caffeine

• Caffeine increases the release of excitatory neurotransmitters by blocking the transmitter (adenosine) that inhibits excitatory neurotransmitters.


Cocaine

• Prevents dopamine from being reabsorbed

• Leads to excess amounts of accumulated dopamine

• Results in heightened arousal of the entire nervous system.


Neural Plasticity and Neurogenesis


Brain Growth and Experience

• Rosenzweig (1984) demonstrated the importance of experience to neural development.


The Central Nervous System


The Central Nervous System

• The nervous system is organized into two parts: – The central nervous system (CNS), which

consists of the brain and spinal cord. – The peripheral nervous system (PNS), is

made up of nerves that radiate throughout the body, linking all of the body's parts to the CNS.


The Brain

• Physically, the brain has three more or less distinct areas: – The central core, – The limbic system, – The cerebrum.


Hindbrain

• Medulla: – Controls breathing, heart rate, blood

pressure

• Pons: – Regulation of sleep/wake cycle

• Cerebellum: – Involved in balance and coordination of

movement


Midbrain

• The relay point for hearing and vision.• One of the places pain is registered.• Brain structures found in midbrain:

– superior colliculus– inferior colliculus – substantia nigra


Forebrain Structures

• Thalamus• Hypothalamus• Cerebral cortex


Forebrain Structures

• Thalamus: – Sensory switchboard

• Hypothalamus: – Governs motivational (hunger, thirst, sex,

sleep, and temperature control) and emotional responses

• Limbic system: – Linked primarily to memory, emotions,

drives


Structures in the Cerebral Cortex

• Frontal lobes• Parietal lobes

– Primary somatosensory cortex– Primary motor cortex

• Temporal lobes• Occipital lobes


Frontal Lobes

• Voluntary movement• Attention• Goal-directed behavior


Parietal Lobes

• Sensations of touch and bodily position• Primary somatosensory cortex:

– Registers and processes body sensations

• Primary motor cortex: – Controls voluntary muscle movement


Temporal Lobe

• Processes information concerning hearing, smell, balance and equilibrium


Occipital Lobes

• Processes information for the sense of vision.


Reticular Formation

• A network of neurons in the hindbrain, midbrain, and part of the forebrain.

• The primary function of this network is to alert and arouse the higher parts of the brain.


The Limbic System

• System of loosely connected structures located between the central core and the cerebral hemispheres.

• Appears to play a central role in times of stress.


The Limbic System

• Hippocampus: – Aids in the processing of memory for

storage

• Amygdala: – Involved in fear and aggression

• Hypothalamus: – Bodily maintenance functions and

pleasurable rewards


Hemispheric Specialization

• The cerebrum consists of two separate cerebral hemispheres.

• The primary connection between the left and right hemispheres is the corpus callosum.

• The corpus callosum allows for close communication between the two hemispheres.


Left Hemisphere

• Right hand touch and movement• Speech• Language• Writing for right handers


Right Hemisphere

• Left hand touch and movement• Spatial construction• Face recognition• Nonverbal imagery• Writing for left handers


Tools for Studying the Nervous System

• Microelectrode techniques: – Used to study the functioning of a single

neuron

• Macroelectrode techniques: – Used to measure cortical activity (e.g., EEG)


Tools for Studying the Nervous System

• Structural imaging: – Study the structures of the brain

• Functional imaging: – Study the functioning of the nervous system


Structural Imaging Techniques

• Computerized Axial Tomography (CAT or CT) scanning

• Nuclear Magnetic Resonance Imaging (NMR or MRI)


Computerized Axial Tomography

• An X-ray photography unit passes a radioactive ray through bone and brain tissue to show structures of the brain.


Magnetic Resonance Imaging

• An MRI uses alterations in the electromagnetic field of the body created by a magnet to measure the movement of nuclei as they return to their original axes.


Functional Imaging Techniques

• Electroencephalograph (EEG)• Magnetoencephalography (MEG) and• Magnetic Source Imaging (MSI)• Positron Emission Tomography (PET)

scanning


MEG and MSI

• These imaging techniques measure the strength of the magnetic field produced by electrical activity in order to identify its source.


Positron Emission Tomography

• PET scans show actual brain activity by measuring radiation in the brain emitted from radioactive water that was injected into the bloodstream.


The Spinal Cord

• The spinal cord is our communications superhighway.

• There are two major pathways in the spinal cord:– The motor neurons– The sensory neurons


Peripheral Nervous System

• The peripheral nervous system (PNS) contains two types of neurons: – afferent neurons, which carry sensory

messages to the central nervous system, – efferent neurons, which carry messages

from the CNS.



• Neurons involved in making voluntary movements of the skeletal muscles belong to a part of the PNS called the somatic nervous system.

• Neurons involved in governing the actions of internal organs belong to a part of the PNS called the autonomic nervous system.



• The autonomic nervous system is divided into two parts: – the sympathetic division, which acts

primarily to arouse the body when it is faced with threat, and

– the parasympathetic division, which acts to calm the body down, restoring it to normal levels of arousal.


Sympathetic Nervous System

• Dilates pupils• No effect on tear glands• Weak stimulation of salivary flow• Accelerates heart, constricts arterioles• Dilates bronchi• Inhibits stomach motility and secretions


Parasympathetic Nervous System

• Constricts pupils• Stimulates tear glands• Strong stimulation of salivary flow• Inhibits heart, dilates arterioles• Constricts bronchi• Stimulates stomach motility & secretion


The Endocrine System

• Endocrine Glands: – Tissues that produce and release hormones

• Hormones: – Chemical substances released by glands

that help regulate bodily activities


Endocrine Glands

• Thyroid gland: – Produces the hormone thyroxin, which

regulates the body’s rate of metabolism

• Parathyroid glands: – Secrete parathormone, which controls and

balances the levels of calcium and phosphate in the blood and tissue fluids


Endocrine Glands

• Pineal gland: – Regulates one’s activity level over the

course of a day

• Pituitary gland: – Produces the largest number of the body’s

hormones

• Posterior pituitary: – Affects thirst, sexual behavior, and perhaps

paternal and maternal behavior


Endocrine Glands

• Anterior pituitary: – Produces hormones that cause other glands

to produce hormones; Regulates body growth and also affects motivation and emotion

• Gonads: – The reproductive glands (testes and

ovaries)


Adrenal Glands

• Adrenal cortex: – Outer covering of the adrenal glands;

Releases hormones important for dealing with stress

• Adrenal medulla: – Inner core of the adrenal glands that also

releases hormones to deal with stress


Pancreas

• An organ lying between the stomach and small intestine.

• It secretes insulin and glucagon to regulate blood-sugar levels.


Genes, Evolution and Behavior

• The related fields of behavior genetics and evolutionary psychology explore the influences of heredity on human behavior.

• Both are helping to settle the nature/nurture debate over the relative contributions of genes and the environment to human similarities and differences.



• Psychologists use a variety of methods to study the contribution of genes in determining variations in certain traits. – Strain studies approach the problem by

observing strains of highly inbred genetically similar animals.

– Selection studies try to determine the extent to which an animal's traits can be passed on from one generation to another.



• Family studies, twin studies, and adoption studies tackle heritability by looking for similarities in traits as a function of biological closeness.

• Molecular genetics focuses on mapping the genes on the chromosomes.


Terminology of Genetics

• Traits: – Characteristics on which organisms differ

• Heredity: – Transmission of traits from one generation

to the next

• Genes: – Elements that control the transmission of

traits; They are found on the chromosomes


Terminology of Genetics

• Chromosomes: – Pairs of threadlike bodies within the cell

nucleus that contain the genes

• Deoxyribonucleic acid (DNA): – The main ingredient of chromosomes and

genes that forms the code for all genetic information


Two Types of Genes

• Dominant: – Member of a gene pair that controls the

appearance of a certain trait

• Recessive: – Member of a gene pair that can control the

appearance of a certain trait only if it is paired with another recessive gene


Animal Behavior Genetics

• Strain studies: – Studies of the heritability of behavioral

traits using animals that have been inbred to produce strains that are genetically similar to one another.

• Selection studies: – Studies that estimate the heritability of a

trait by breeding animals with other animals that have the same trait.


Human Behavior Genetics

• Family studies: – Studies of heritability based on the

assumption that if genes influence a certain trait, close relatives should be more similar on that trait than distant relatives.

• Twin studies: – Studies of identical and fraternal twins to

determine the relative influence of heredity and environment.


Types of Twins

• Identical: – Twins developed from a single fertilized

ovum.

• Fraternal: – Twins developed from two separate

fertilized ova.


Adoption Studies

• Research carried out on children who were adopted at birth by parents not related to them.

• The goal of this type of research is to determine the relative influence of heredity and environment on human behavior.


Evolutionary Psychology

• Evolutionary psychology analyzes human behavioral tendencies by examining their adaptive value from an evolutionary perspective.

• It has proved useful in helping to explain some of the commonalities in human behavior that occur across cultures.


Ethical Issues

• Manipulating human genes in an effort to change how people develop is a new technology that makes many people uneasy.

• These concerns may be exaggerated because genes are not all-powerful.

• Heredity and environment play a part in shaping most significant human behaviors and traits.

©prentice hall 20032-1 understanding psychology 6 th edition charles g. morris and albert a. maisto...

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