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.

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+ Cl- K+ INSIDE Cross-section of nerve cell showing distribution of ions across the membrane © 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 K ions out NA ions in © 2002 John Wiley & Sons, Inc.

Details of the Synapse © 2002 John Wiley & Sons, Inc.

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 © 2002 John Wiley & Sons, Inc.

Development of the Brain (Figure adapted from Kold & Wishaw, 1990) © 2002 John Wiley & Sons, Inc.

Midline View of Human Brain Medulla: Controls heart rate, respiration Cerebellum: Coordinates smooth movements, balance, and posture Pons: 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 © 2002 John Wiley & Sons, Inc.

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 © 2002 John Wiley & Sons, Inc. (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.