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Chapter 2: The Biological Bases of Behavior
Paul J. Wellman
Texas A&M University
Psychology in Action, Fifth Edition
by
Karen Huffman, Mark Vernoy, and
Judith Vernoy
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Lecture Overview
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Neurons
Neurotransmitters and Hormones
The Peripheral Nervous System
The Brain
Methods Used to Study the Brain
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Neurons
• Neurons are cells that transmit
information
• Neurons are composed of:
– Cell body
– Dendrites: extensions that receive
information
– Axon: extends from cell body, carries
electrical potential, sends a chemical
message to adjacent neurons
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
The Neuron
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
The Action Potential
• The membrane of the axon carries an
electrical charge:
– The area inside the axon membrane is
more negative than is the outside (termed
the resting membrane potential)
– The RMP is usually about -70 mV
• Action potential occurs when the
membrane potential rapidly shifts from
-70 to +40 mV.
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
The Action Potential
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Synapse
• The synapse is the junction between an
axon terminal and an adjacent dendrite
• Neurotransmitters are released from the
axon terminal in response to an action
potential into the synapse
– The molecules diffuse across the synapse
– NT molecules interact with receptors to alter
the potential of the membrane
• May lead to an action potential in the adjacent cell
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
The Synapse
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Action Potentials
• AP’s are fixed in amplitude
• An AP sweeps along the axon
membrane at a constant velocity
• Vary in frequency (a few per second to
a max of 1000 per second)
• Are “all or none” in nature (AP either
occurs or it does not)
• AP’s have a refractory period
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Psychoactive Drugs
• Psychoactive drugs affect the nervous
system to alter mood, emotion and
thought
• Psychoactive drugs act by
– Releasing neurotransmitters
• Amphetamine releases dopamine
– Stimulating or blocking neuron receptors
• Alcohol depresses neuron function
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
The Endocrine System
• Hormones are
secreted into the
blood by the
endocrine system
• Hypothalamus
controls hormone
release
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Peripheral Nervous System
• The Peripheral Nervous System (PNS)
includes all nerves outside the brain and
spinal cord
– Somatic NS carries sensory messages to
brain and motor commands to the muscles
– Autonomic N.S. regulates automatic body
functions (heart rate, breathing)
• Sympathetic: “Fight or Flight”
• Parasympathetic: Active during digestion
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
The Autonomic Nervous System
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Central Nervous System
• The CNS is composed of the brain and
spinal cord
• Spinal cord connects the brain with the
PNS
– Comprised of cell bodies and axons that
carry messages
• Afferent: toward the brain
• Efferent: away from the brain
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Overview of Brain
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Cerebral Cortex
• Cortex refers to the outer covering of
the brain
– Consists of 2 hemispheres (left and right)
• Cortex is divided into lobes
– The lobes carryout different functions
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Frontal: Self awareness and planning
Parietal: Body sensations
Occipital: Vision
Temporal: Hearing
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Cortical Lobes
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Subcortical Brain Areas
• Corpus callosum: band of axons that
interconnects the 2 hemispheres
• Thalamus: sensory relay area
• Limbic system: involved in emotionality
• Hypothalamus: feeding, fleeing, mating,
and fighting
• Cerebellum: involved in motor control
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Midline Brain View
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Brainstem
• Brainstem: primitive portion of brain
– Pons
– Medulla
– Reticular activating system
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Studying the Brain
• Neuroscientists learn about the function
of the brain via:
– Lesion studies: a brain region is destroyed
and behavior is observed
• Lesions of hypothalamus---> overeating
– Electrical Recording: overall brain wave
activity is monitored by the EEG
– Imaging techniques allow the living brain to
be studied for its activity during behavior
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e
Copyright
Copyright 2000 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.
© 2000 John Wiley & Sons, Inc.
Huffman/Vernoy/Vernoy: Psychology in Action 5e