1. P S Y C H O L O G Y T 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.

2. Lecture Outline Neurons and nerve potentials The Nervous system
Cerebral lateralization
Behavioral genetics
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3. 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
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4. 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
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5. 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+
Cl- K+
INSIDE
Cross-section of nerve
cell showing
distribution of ions
across the membrane
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6. 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)
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7. 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
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8. Overview of the Action Potential
K ions
out
NA ions in
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9. Details of the Synapse
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10. 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
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11. 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
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12. Overview of the Nervous System
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13. 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)
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14. Autonomic Nervous System
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15. Overview of the Spinal Cord
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16. Development of the Brain
(Figure adapted from Kold & Wishaw, 1990)
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17. Midline View of Human Brain
Medulla: Controls heart rate, respiration
Cerebellum: Coordinates smooth movements, balance, and posture
Pons: Involved in the control of sleep
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18. 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)
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19. 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
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20. The Cortical Lobes of the Human Brain
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21. 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.
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22. 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
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23. 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
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24. Split-Brain Studies © 2002 John Wiley & Sons, Inc.
(Figure adapted from Gazzaniga, 1967)
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25. 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
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26. 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
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27. 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.
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