Chapter 3

Psychology: Brain, Mind, and Culture, 2e

by Drew Westen

Paul J. Wellman

Texas A&M University

John Wiley and Sons, Inc.

PowerPoint Presentation: Chapter 3

Biological Bases of Mental Life and Behavior

Lecture Outline

Neurons and nerve potentials Neurotransmitters The Nervous system Cerebral lateralization Behavioral genetics

© 1999 John Wiley and Sons, Inc.

Neurons

Neuron: A cell that specializes in the transfer of information within the nervous system

Three classes of neurons:• Sensory: Transmit information from sensory

receptors to the brain (afferent)• Motor: Transmit commands from the brain to the

muscles and glands of the body (efferent)• Interneurons: Interconnect neurons


Components of the Neuron

Dendrites: receive information

Cell body Axon

• Myelin insulates the nerve cell, speeds up conduction of nerve messages

• Terminal buttons of the axon release transmitter


Neuron Resting Potentials The membrane of the neuron

separates charges The ions NA+ and Cl- are found

outside the membrane whereas the ion K+ is inside the membrane

The membrane is slightly permeable to K+, so that at rest, the inside is about -70 millivolts relative to the outside

At rest, little NA+ crosses the membrane

NA+

K+

Cl-

Cross-section of nerve cell showing distribution of ions across the membrane

INSIDE


Graded Potentials Stimulation of the nerve

membrane can open ion channels in the membrane

• NA+ ions flowing in will depolarize the membrane (movement from -70 mV to say -60 mV

• K+ ions flowing out of membrane will hyperpolarize the membrane (-70 mV to say -90 mV)

Time

-70

0

+40

RMP


The Action Potential

If the graded potential passes threshold, NA+ ions flow into the cell raising the membrane potential to +40 mV, producing the spike The restoration of the membrane potential to -70

mV is produced by an opening of channels to K+

NA+

K+


Details of the Synapse The synapse is the

physical gap that separates the axon terminal from the dendrite Presynaptic vs.

postsynaptic membranes


Neurotransmitters Neurotransmitters are chemicals

• Stored within vesicles of the presynaptic cell• Released in response to the action potential sweeping

along the presynaptic membrane• Transmitter molecules diffuse across the synaptic cleft

and bind to postsynaptic receptors• Receptor binding opens or closes ion channels:

– NA channel opening: Depolarizes the membrane– K+ channel opening: Hyperpolarizes the membrane

Neuromodulators: Indirectly alter the activity of other transmitter substances


Endocrine Systems Endocrine glands release

hormones into blood stream

• Have effects at diffuse target sites throughout the body

• Hormones bind to receptors • Hormones can have

organizational effects (permanent change in structure and function)


Overview of the Nervous System


The Autonomic Nervous System (ANS) Two branches of the ANS:

• Sympathetic: Emergency system

• Parasympathetic: Vegetative functions (e.g. digestion)

The two systems often act in opposition (as in the control of heart rate)

Can act in concert (as in the control of sexual reflexes)


Overview of the Spinal Cord


Evolution of the Brain


(Figure adapted from Kolb & Wishaw, 1990)

Midline View of Human Brain

Medulla: Controls heart rate, respirationCerebellum: Coordinates smooth movements, balance, and posturePons: Involved in the control of sleep


Anatomy of the Limbic System Septal area is involved in

pleasure and in relief from pain

Amygdala is involved in learning and recognition of fear

Hippocampus is involved in memory

• Patient H.M. shows anterograde amnesia (cannot learn new information)


Cerebral Cortex Functions of cerebral cortex:

• Provides for flexible control of patterns of movement• Permits subtle discrimination among complex

sensory patterns• Makes possible symbolic thinking

– Symbolic thought is the foundation of human thought and language

Functional organization of cortex:• Primary areas• Association areas


The Cortical Lobes of the Human Brain


Organization of Sensory and Motor Cortex


(Figure adapted from Penfield & Rasmussen, 1978)

Frontal Lobe Damage and Personality

Frontal lobes are involved in movement, attention, planning, memory, and personality.

Frontal lobe function in personality is evident in the case of Phineas Gage

• Gage suffered frontal lobe damage after an accident involving a dynamite tamping rod

• Gage was a railroad supervisor prior to the damage; after the damage he became childish and irreverent, could not control his impulses, and could not effectively plan.


Cerebral Lateralization The structures of the cortex and sub-cortex appear to

specialize in function:• Hemispheric Specialization

– Left hemisphere is dominant for language, logic, and complex motor behavior.

– Right hemisphere is dominant for non-linguistic functions including recognition of faces, places, and sounds (music)

– The hemispheric specializations are evident from studies of» Damage to one hemisphere (I.e. Broca’s area)» Split-brain subjects

• Gender differences in brain lateralization– Issue is whether the brains of males and females may be organized

differently and whether such organization might have functional significance


The Split-Brain Study Information from the one visual

field is usually transmitted to the opposite visual cortex

The corpus callosum serves to integrate the two hemispheres

Cutting the corpus callosum can result in information only reaching one hemisphere


(Figure adapted from Gazzaniga, 1967)

Behavioral Genetics Behavioral genetics is concerned with the

influence of genes on psychological function• Genotype: Genetic structure (DNA located on chromosomes)

• Phenotype: Observable psychological function

Relatedness is the probability of sharing a gene with parents and others

Heritability: Quantifies the extent to which variations in a trait across persons can be accounted for by genetic variation


Heritability of Psychological Traits

Studies of twins raised apart suggest heritability coefficients of 0.15 to 0.50 for the traits of:

• Conservatism• Neuroticism• Aggressiveness• Intelligence• Likelihood of divorce• Job satisfaction• Vocational interests


Copyright

Copyright 1999 by John Wiley and Sons, New York, NY. All rights reserved. No part of the material protected by this copyright may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission of the copyright owner.


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