Transcript 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 © 1999 John Wiley and Sons, Inc. 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 © 1999 John Wiley and 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 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 © 1999 John Wiley and Sons, Inc. NA Cl- + K+ INSIDE Cross-section of nerve cell showing distribution of ions across the membrane Graded Potentials Stimulation of the nerve membrane can open ion +40 channels in the membrane 0 • NA+ ions flowing in will depolarize the membrane (movement from -70 mV to say-70 -60 mV • K+ ions flowing out of membrane will hyperpolarize the membrane (-70 mV to say -90 mV) © 1999 John Wiley and Sons, Inc. RMP Time K+ The Action Potential NA+ 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+ © 1999 John Wiley and Sons, Inc. Details of the Synapse The synapse is the physical gap that separates the axon terminal from the dendrite Presynaptic vs. postsynaptic membranes © 1999 John Wiley and Sons, Inc. 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 © 1999 John Wiley and 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) © 1999 John Wiley and Sons, Inc. Overview of the Nervous System © 1999 John Wiley and Sons, Inc. 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) © 1999 John Wiley and Sons, Inc. Overview of the Spinal Cord © 1999 John Wiley and Sons, Inc. Evolution of the Brain (Figure adapted from Kolb & Wishaw, 1990) © 1999 John Wiley and 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 © 1999 John Wiley and Sons, Inc. 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) © 1999 John Wiley and 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 © 1999 John Wiley and Sons, Inc. The Cortical Lobes of the Human Brain © 1999 John Wiley and Sons, Inc. Organization of Sensory and Motor Cortex (Figure adapted from Penfield & Rasmussen, 1978) © 1999 John Wiley and 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. © 1999 John Wiley and 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 © 1999 John Wiley and 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 only reaching one hemisphere (Figure adapted from Gazzaniga, 1967) © 1999 John Wiley and 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 © 1999 John Wiley and 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 © 1999 John Wiley and Sons, Inc. 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. © 1999 John Wiley and Sons, Inc.