P S Y C H O L O G YT h i r d E d i t i o n

by

Drew Westen

PowerPoint Presentation

C h a p t e r 3 B I O L O G I C A L B A S E S O F

M E N T A L L I F E & B E H A V I OR

John Wiley & Sons, Inc.

Lecture Outline

Neurons and nerve potentials The Nervous system Cerebral lateralization Behavioral genetics

© 2002 John Wiley & Sons, Inc.

Neurons Neurons are cells that specialize 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

© 2002 John Wiley & Sons, Inc.

Components of the Neuron Dendrites: receive

information from other neurons

Cell body: creates transmitter molecules

Axon• Myelin insulates the nerve

cell, speeds up conduction of nerve messages

• Terminal buttons of the axon release transmitter

© 2002 John Wiley & Sons, Inc.

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 mostly inside the membrane

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

At rest, few NA+ ions are able to cross the membrane

NA+

K+

Cl-

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

INSIDE

© 2002 John Wiley & Sons, Inc.

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)

© 2002 John Wiley & Sons, Inc.

The Action Potential Graded potentials are generated at the dendrites and are conducted

along the membrane to the axon hillock If the summated activity at the axon hillock raises the membrane potential

past threshold, an action potential (AP) will occur During the AP, 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+ The AP is conducted along the axon toward the terminals

© 2002 John Wiley & Sons, Inc.

Overview of the Action Potential

NA ionsin

K ionsout

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Details of the Synapse

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Synaptic Functioning Neurotransmitters (NTs) are chemicals

NTs are stored within vesicles of the presynaptic cell NTs are 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

© 2002 John Wiley & Sons, Inc.

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)

Hormones can have activational effects:

• Lack of testosterone lack reduces sexual behavior

© 2002 John Wiley & Sons, Inc.

Overview of the Nervous System

© 2002 John Wiley & Sons, Inc.

Autonomic Nervous System The Autonomic Nervous System (ANS) has

two divisions: 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)

© 2002 John Wiley & Sons, Inc.

Autonomic Nervous System

© 2002 John Wiley & Sons, Inc.

Overview of the Spinal Cord

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Development of the Brain

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(Figure adapted from Kold & Wishaw, 1990)

Midline View of Human Brain

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

© 2002 John Wiley & Sons, Inc.

Limbic System Functions 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)

© 2002 John Wiley & Sons, Inc.

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

© 2002 John Wiley & Sons, Inc.

The Cortical Lobes of the Human Brain

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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.

© 2002 John Wiley & Sons, Inc.

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

© 2002 John Wiley & Sons, Inc.

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 reaching only one hemisphere Language is a left-hemisphere function Information reaching the left hemisphere will be

reported by the subject, but not information reaching the right hemisphere

© 2002 John Wiley & Sons, Inc.

Split-Brain Studies

(Figure adapted from Gazzaniga, 1967)

© 2002 John Wiley & Sons, Inc.

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

© 2002 John Wiley & Sons, Inc.

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

© 2002 John Wiley & Sons, Inc.

Copyright

Copyright 2002 by John Wiley & Sons, Inc., 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.

© 2002 John Wiley & Sons, Inc.