Neuroscience

Psychology: A Concise Introduction

2nd Edition

Richard Griggs

Chapter 2

Prepared byJ. W. Taylor V

The Journey…

The Neuron

The Nervous System and the Endocrine System

The Brain

The Neuron

The Nervous System and the Endocrine System

The Brain

The Neuron

The Structure of a Neuron

How Neurons Communicate

Neurotransmitters, Drugs, and Poisons

Neurons and Glial Cells

Neurons are responsible for information transmission throughout the nervous system

Glial cells do not directly transmit information, but instead support neurons in their work by disposing of waste products of neurons, keeping their chemical environment stable, and insulating them

The Structure of a Neuron Dendrites are the fibers that

project out of the cell body, receiving information from other neurons

The cell body contains the nucleus of the cell and other biological machinery to keep the cell alive

The axon transmits messages through the neuron

The axon terminals are at the end of the axon and send messages to a different neuron

The Structure of a Neuron

How Neurons Communicate

Communication within

a neuron is electrical

Communication within

a neuron is electrical

Communication between

neurons is chemical

Communication between

neurons is chemical

The Electrical Impulse

Information from the dendrites is either excitatory (telling the neuron to generate an electrical impulse) or inhibitory (telling the neuron not to generate an electrical impulse) The impulse is an “all or nothing” event, meaning

that there either is or is not an electrical impulse Stimuli of varying intensities are encoded by the

quantity of neurons generating impulses and the number of impulses generated each second by the neurons

The Electrical Impulse

The myelin sheath is an insulating layer of fatty white substance that encases the axon, allowing electrical message to be transmitted faster within the neuron Damage to the myelin sheath will slow electrical

impulses, and can result in diseases like multiple sclerosis

Chemical Communication Between Neurons

Axon terminals contains sacs of neurotransmitters These neurotransmitters are naturally occurring

chemicals in the nervous system that specialize in transmitting information between neurons

Between the axon terminals of one neuron and the dendrites of another neuron is a small space called the synaptic gap, across which neurotransmitters are sent, allowing neurons to communicate

Brain Scans

Brain scans work because neurons require oxygen and other nutrients such as blood sugar Positron Emission Tomography (PET) scans

use a dose of radioactive glucose, which moves to the more-active areas of the brain

Functional Magnetic Resonance Imaging (MRI) detects active areas of the brain by highlighting those areas that require more oxygen

Neurotransmitters, Drugs, and Poisons

Key terms:

AgonistsAgonists AntagonistsAntagonists

Drugs and poisons that increase the activity of one or more neurotransmitters

Drugs and poisons that decrease the activity of one or more neurotransmitters

Neurotransmitters

1. Acetylcholine (ACh) is involved in both learning and memory and muscle movement

2. Dopmaine impacts our arousal and mood states, thought processes, and physical movement

3. Serotonin and norepinephrine are neurotransmitters involved in levels of arousal and mood, and play a major role in mood disorders such as depression

4. GABA is the main inhibitory neurotransmitter in the nervous system; glutamate is the main excitatory neurotransmitter

5. Endorphins are a group of neurotransmitters that are involved in pain perception and relief

Acetylcholine (ACh)

Botulinum poison (botulin) is an antagonist that blocks the release of ACh at muscle junctures, leading to paralysis and even death

Curare is an antagonist that paralyzes the body by occupying the receptor sites for ACh, thereby preventing ACh from getting in and carrying its message to a neuron

Black widow spider venom is an agonist for Ach, causing the continuous release of ACh, flooding the synapse

Dopamine

Low levels are associated with Parkinson’s disease, and excessively high levels are associated with schizophrenia

L-Dopa is an agonist that increases production of dopamine

Anti-psychotic drugs are antagonists that block the receptor sites for dopamine so that this neurotransmitter cannot send its messages

Amphetamine acts as an agonist by stimulating the release of dopamine from axon terminals

Cocaine is an agonist that blocks the re-uptake of dopamine

Serotonin and Norepinephrine

Some antidepressant drugs work by blocking the reuptake of serotonin and norepinephine

Anti-depressant drugs like Prozac, Paxil, and Zoloft are selective serotonin reuptake inhibitors

GABA and Glutamate

Anti-anxiety drugs are agonists for GABA Lack of GABA may contribute to epilepsy, a

brain disorder resulting in uncontrolled movement and convulsions

Glutamate is involved in memory storage and pain perception.

Excessive glutamate can lead to neuron death; deficient glutamate has been proposed to explain schizophrenia

Endorphins

Morphine and heroin are agonists that bind to receptor sites, thereby increasing endorphin activity

The Nervous and Endocrine Systems

The Central Nervous System

The Peripheral Nervous System

The Endocrine Glandular System

Emotions and the Autonomic Nervous System

Nervous System Subdivisions

Types of Neurons

Interneurons exist only in the central nervous system

Sensory neurons carry information to the central nervous system from sensory receptors in the eyes, muscles, and glands

Motor neurons carry movement commands from the central nervous system to the rest of the body

The Central Nervous System

Consists of the spinal cord and the brain The spinal cord has two functions

Conduit for incoming sensory data and outgoing movement commands

Provides for spinal reflexes, which are simple automatic actions not involving the brain

The brain is the control center for the entire nervous system

The Peripheral Nervous System

Gathers information about the external environment and the body’s internal environment for the brain through sensory neurons

Serves as the conduit for the brain’s commands to the rest of the body through motor neurons

The Peripheral Nervous System

Consists of two parts: The somatic (or skeletal) nervous system carries

sensory input from receptors to the CNS and relays commands from the CNS to the skeletal muscles to control their movement

The autonomic nervous system regulates our internal environment and consists of two parts The sympathetic nervous system is in control when we

are very aroused and prepares us for defensive action (such as running away or fighting)

The parasympathetic nervous system is in control when the aroused state ends to return our body to its normal resting state

The Endocrine Glandular System

Not part of the nervous system Works with the autonomic nervous system in

responding to stress, and plays a role in basic behaviors and bodily functions such as sex, eating, metabolism, reproduction, and growth

Endocrine glands secret hormones, which are chemicals carried by the bloodstream to target sites throughout the body

The Endocrine Glandular System

Endocrine glands are controlled by the hypothalamus, which controls the most influential gland, the pituitary Releases hormones essential for human growth and that

direct other glands to release their hormones

Some other glands: Thyroid gland affects our growth and maturation Adrenal glands are involved in metabolism and help

trigger the “fight or flight” response with commands from the autonomic nervous system

The pancreas is involved in digestion and maintaining blood-sugar levels

The Endocrine Glandular System

Components of Emotion

An emotion is a complex psychological state that involves three components:

An emotion is a complex psychological state that involves three components:

PhysicalPhysical BehavioralBehavioral CognitiveCognitive

A physiological state of arousal triggered by the

autonomic nervous system

An outward expression including facial expressions,

movements and gestures

An appraisal of the situation to determine which emotion we are experiencing and how

intensely

Components of Emotion

The physical component Includes the “fight or flight” response of the autonomic nervous

system Heart rate and breathing increase, blood pressure surges, start

sweating, pupils dilate, digestion slows The behavioral component

Is the product of motor neurons The facial-feedback hypothesis assumes that the facial muscles

send messages to the brain, allowing the brain to determine which emotion is being experienced

The cognitive component Includes an appraisal of the situation to determine what emotion

we are experiencing

Theories of Emotion

James-Lange Theory James-Lange Theory

Cannon-Bard Theory Cannon-Bard Theory

Schachter-Singer Two-Factor Theory

Schachter-Singer Two-Factor Theory

James-Lange Theory

Contends that autonomic nervous system physiological arousal is a response to a stimulus, and that such a physiological response is subsequently interpreted as the emotion

For example, if you are crossing the street and see a car speeding toward you, your autonomic nervous system is aroused (e.g., increased heart rate). Based on this arousal, you interpret the stimulus as threatening and pick up your pace across the street.

Cannon-Bard Theory

Contends that arousal patterns for different emotions are too physiologically alike to be able to determine what emotion is being experienced

Instead, an emotion-provoking stimulus sends messages to both the peripheral nervous system and the brain The brain produces the emotional feeling, the

autonomic nervous system produces the physiological response, and the motor neurons produce the behavioral response

Schachter-SingerTwo-Factor Theory

Contends that there are two important determinants of emotion: Physiological arousal tells us how intense the

emotion is The cognitive appraisal of the entire situation

allows us to identify the emotion, leading to the emotional feeling

Integrating the Theories

LeDoux (1996) contends that there are different brain systems for different emotions Fear, for example, does not require higher-level

cognitive processing and is generated almost instantaneously by the amygdala

More complex emotions, however, such as love or guilt, that do not require instantaneous responding for survival, may require higher-level processing

The Brain

Going up the Brain Stem

Processing in the Cerebral Cortex

Specializations of the Left and Right Hemispheres

Consciousness and the Sleeping Brain

Case 1: A Landscape Artist

Scenario Neuroanatomy Related Function

Anne the landscape artist is standing at her easel, painting with her right hand as she looks out the window at her garden. She’s listening to classical music as she paints.

Left motor cortex Left frontal lobe Visual cortex Both occipital lobes Auditory cortexes Both temporal lobes Right hemisphere Thalamus Frontal lobes Left sensory cortex Left parietal lobe Cerebellum

Controls right hand Contains motor cortex Used for vision Contain visual cortex Used to hear music Contain auditory cortexes Spatial ability for painting Relays sensory information Deciding what to paint Feeling the paintbrush Contains sensory cortex Coordinates moving arm

Case 2: A Professional Wrestler

Scenario Neuroanatomy Related Function

Crazy Eddie, the professional wrestler, is in the ring wrestling. The crowd is yelling and his is taunting him. Eddie yells back at his opponent. The two of them are out of breath and sweating profusely. They continue their well-orchestrated series of wrestling moves.

Both motor cortexes Frontal lobes Both sensory cortexes Parietal lobes Visual cortexes Both occipital lobes Right hemisphere Wernicke’s area Left temporal lobe Broca’s area Left frontal lobe Thalamus Frontal lobes Medulla Amygdala Reticular formation Cerebellum Hypothalamus Hippocampus

Move muscles Contain motor cortexes Needed for sense of touch Contain sensory cortexes Used for vision Contain visual cortexes Spatial ability for wrestling Understanding taunts Contains Wernicke’s area Produces speech (yells) Contains Broca’s area Sensory relay Decision making & attention Regulates heart and breathing Aggression and fear Controls arousal Balance and coordination Regulates temperature Memory for moves

Case 3: A Student

Scenario Neuroanatomy Related Function

Jill is a law student studying for her exam. She is reading about violent rape and murder cases. She is snacking on popcorn and drinking coffee.

Hippocampus Wernicke’s area Left temporal lobe Amygdala Frontal lobes Hypothalamus Angular gyrus

Remembering and learning Language comprehension Contains Wernicke’s area Anger and fear about cases Decision making & attention Regulates hunger and thirst Needed for reading

Source: Sheldon, J. P. (2000). A neuroanatomy teaching activity using case studies and collaboration. Teaching of Psychology, 27, 126-128.

The Central Core

The brain stem The medulla links the spinal cord to the brain and is involved in

regulating heartbeat, blood pressure, digestion, and swallowing The reticular formation is a network of neurons running up the

center of the brain stem and into the thalamus that is involved in controlling our different levels of arousal and awareness

The cerebellum is involved in the coordination of our movements, our sense of balance, and motor and procedural learning

The thalamus, located at the top of the brain stem, serves as a relay station for incoming sensory information (except smell) The basal ganglia are on the outer sides of the thamalus and are

concerned mainly with the initiation and execution of physical movements

The Central Core Brain Structures

The Limbic System

Plays a role in our survival, memory, and emotions The hypothalamus control the pituitary gland, the

autonomic nervous system, and plays a major role in regulating basic drives such as eating, thirst, and sex

The hippocampus is involved in the formation of memories

The amygdala plays a major role in regulating our emotional experiences, especially fear, anger, and aggression

The Limbic System

Processing in the Cerebral Cortex

The cerebral cortex is the most important brain structure, serving as the information processing center for the nervous system Is where perception, language, memory, decision

making, and all other higher-level cognitive processing occur

Consists of two hemispheres connected by a band of neurons called the corpus callosum, allowing the two hemispheres to communicate

Brain Lobes

1. The frontal lobe is the area in the front of each hemisphere and in front of the central fissure and above the lateral fissure

2. The parietal lobe is the area located behind the central fissure and above the lateral fissure

3. The temporal lobe is located beneath the lateral fissure

4. The occipital lobe is located in the lower back of each hemisphere

The Four Lobes and the Sensory-Motor Processing Areas

The Motor Cortex

The frontal lobe strip of cortex, directly in front of the central fissure in each hemisphere, allows us to move different parts of our body

Each hemisphere controls the voluntary movement of the opposite side of the body (a contralateral relationship)

Amount of motor cortex devoted to a specific body part is related to the complexity and precision of movement of which that part is capable

The Somatosensory Cortex

The parietal lobe strip of cortex, directly behind the central fissure in each hemisphere, is where body sensations of pressure, temperature, limb position, and pain are processed Contralateral relationship Amount of sensorimotor cortex devoted

to a body part is directly proportionate to the sensitivity of that body part

Homunculi for the Motor Cortex and the Somatosensory Cortex

Visual Cortexand Auditory Cortex

The visual cortex is located in the occipital lobes at the back of the hemispheres

The auditory cortex is in the temporal lobes These primary areas pass the

results of their analyses on to areas in the other lobes to complete the brain’s interpretation of the incoming visual or auditory information These secondary cortical processing

areas are part of what is termed the association cortex

Association Cortex

Consists of the other 70% of the cortex not in one of the previously mentioned areas

This is where the higher-level processing such as decision making, reasoning, perception, speech, and language occurs All of which require integration of various types

of information

The Case of Phineas Gage

Phineas Gage was railroad worker who survived when a metal tamping iron flew through his left cheek and head, exiting through his frontal lobes

He became irresponsible, impulsive, disorderly, indecisive, and cursed, leading neuroscientists to think the frontal lobes are important in such behaviors

Language

Broca’s area, in the left hemisphere’s temporal lobe, is responsible for fluent speech production When damaged, people cannot generate fluent speech,

but can still understand speech easily Singing and musical abilities seem to be housed in the

right hemisphere because damage to Broca’s area does not impair these abilities

Wernicke’s area is in the left temporal lobe and is responsible for the comprehension of speech and reading

Language

Studying the Two Hemispheres

Light waves from the left visual field go to the right half of each eye, and light waves from the right visual field go to the left half of each eye The right half of each eye connects with the

right hemisphere, and the left half of each eye connects with the left hemisphere

Pathways for Processing Information in the Left and Right Visual Fields

Studying the Two Hemispheres

With split-brained people, the information cannot transfer between hemispheres because the corpus callosum has been cut

Split-brain people can only identify information orally when it is presented briefly in the right visual field (and thus processing in the left hemisphere) If a spoon was flashed in the left visual

field, split-brained people could not say it was a spoon

If the person was blind-folded and told to find the object from a group of objects with the left hand, s/he can do this

What we know…

Left hemisphere Language Math and logic skills More analytical, analyzing wholes into pieces

Right hemisphere Spatial perception Solving spatial problems Drawing Face recognition

What we know…

Remember, however, that these differences in hemispheric performance are for people whose two hemispheres can no longer communicate

When normal people are performing a task, the two hemispheres are constantly interacting and sharing information

This is why it is not very accurate to say someone is “left-brained” or “right-brained”

Rather, nearly all of us are “whole brained”

Consciousness and the Sleeping Brain

Consciousness is a person’s subjective awareness of both their inner thinking and feeling and their external environment

The five stages of sleep were determined by use of an electroencephalogram (EEG), which records a real-time graph of a person’s cortical electrical activity in the brain As we slip into sleep and pass through the first four

stages, our brain waves change, in general becoming progressively slower, larger, and more irregular, especially in Stages 3 and 4

Five Stages of Sleep

Stage 1: Lasts about 5 minutes Stage 2: Lasts about 20 minutes

Characterized by sleep spindles, rapid bursts of mental activity

Stage 3: Also known as transitional sleep and is characterized by delta waves, which are large, slow waves

Stage 4: Lasts about 30 minutes Parasympathetic nervous system is active, as

muscles relax, heartbeat slows, blood pressure declines, and digestion speeds up

Five Stages of Sleep

Stage 5: REM (rapid eye movement sleep) occurs after we leave stage 4 sleep and return through the earlier stages of sleep Called paradoxical sleep because your muscles are relaxed, but

other body systems, including the brain, are active, much like a waking pattern

Characterized by very rapid brain waves somewhat like those of Stage 1 sleep, but one is still sound asleep

If awakened during REM sleep, people often report having been dreaming

Most dreams are emotional and unpleasant, perhaps because the visual cortex and frontal lobe are inactive during REM sleep; the limbic system structures are active, however, creating irrational imagery and emotional experiences of our dream world

REM sleep accounts for 20–25% of total sleep time

Five Stages of Sleep

Five Stages of Sleep

These 5 stages (the sleep cycle) repeat themselves about every 90 minutes, with Stages 3 and 4 getting shorter with each cycle, and REM and Stage 2 getting longer with each cycle

REM sleep rebound effect is a significant increase in the proportion of REM sleep following deprivation of REM sleep

Why do we sleep and dream?

Sleep deprivation results in: Impaired concentration and a general bodily feeling of

weakness and discomfort Suppression of the immune system, lessening one’s

ability to fight off infection and disease Increased vulnerability to accidents Increased difficulty in concentrating, studying, and

taking exams

Why do we sleep and dream?

Explanations for dreaming : Sigmund Freud proposed that dreams were

disguised outlets for inner conflicts of our unconscious mind, a view not accepted by modern sleep researchers

The activation-synthesis hypothesis contends that dreams are merely the sleeping brain’s attempt to make sense of random neural activity without the rational interpretation of the frontal lobe