Chapter 3
The Biological Bases of
Behavior
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Biological Psychology
• The study of the cells and organs of the
body and the physical and chemical
changes involved in behavior and
mental processes
• What is the relationship between one’s
body and one’s mind?
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The Complex Relationship
Between Our Brain and Our Behavior
Biological
Processes
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Environment
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Figure 3.1
Three Functions of the Nervous System
Cells of the Nervous System
• Neurons: Specialized cells that rapidly
respond to signals and quickly send
signals of their own
• Glial cells: Cells that help hold neurons
together and help neurons
communicate with one another
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Figure 3.2 The Neuron
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2) What Cells Make Up the Nervous
System?
• Cell Body- contains nucleus
which provides energy for the
neuron (C)
• Dendrites- receive messages
from other neurons (B)
• Axon- carry information away
from the cell body (D).
• Axon Terminals- transmit signals
to the dendrites (E).
• Myelin Sheath- A substance that
speeds up the firing of the neuron
(F).
• Nodes of Ranvier- Name for the
small gaps on the neuron that
have no myelin covering (A).
Axon
• Function: Carries signals way from the
cell body
• Type of Signal Carried: The action
potential, an all-or-nothing
electrochemical signal that shoots down
the axon to vesicles at the tip of the
axon, releasing neurotransmitters
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Dendrite
• Function: Detects and carries signals
to the cell body
• Type of Signal Carried: The
postsynaptic potential, which is an
electrochemical signal moving toward
the cell body
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Synapse
• Function: Provides an area for the
transfer of signals between neurons,
usually between axon and dendrite
• Type of Signal Carried: Chemicals that
cross the synapse and reach receptors
on another cell
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Neural transmission
• http://science.education.nih.gov/supple
ments/nih2/addiction/activities/lesson2_
neurotransmission.htm
• http://science.education.nih.gov/supple
ments/nih2/addiction/activities/lesson3_
cocaine.htm
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Receptors
• Function: Proteins on the cell
membrane that receive chemical signals
• Type of Signal Carried: Recognizes
certain neurotransmitters, thus allowing
it to begin a postsynaptic potential in
the dendrite
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Neurotransmitter
• Function: A chemical released by one
cell that binds to the receptors on
another cell
• Type of Signal Carried: A chemical
message telling the next cell to fire or
not to fire its own action potential
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Communication Between
Neurons
• An action potential triggers the release of neuotransmitters
– Neurotransmitters are chemicals that help neighboring neurons talk to
each other.
– These chemicals float from the synaptic vessel of one neuron and are
taken up by the Neurotransmitter receptors in neighboring neuron.
– Synapse - small space between neurons.
• Plasticity - repeated release of neurotransmitters can cause
permanent change to the neurons.
The Action Potential
• Stimulation causes cell membrane to
open briefly
• Positively charged sodium ions flow in
• Very brief shift in electrical charge that
travels along axon
• Action potential-which is a shortlived change in electric charge inside
the neuron.
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All or none “law”
• neuron either fires and generates an
action potential, or doesn’t.
• Stronger stimuli do not send stronger
impulses-> send impulses at a faster
rate--- OR involve more neurons.
•
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Figure 3.5
Communication
Between
Neurons
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Figure 3.3
The Beginning of an Action Potential
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Impulse
Presynaptic neuron
Vesicle
Transmitters
Synaptic cleft
Postsynaptic
neuron
Receptors
Postsynaptic activity
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Termination of Neurosynaptic
Transmission
• Reuptake:
• Enzymatic degradation
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Small Molecule Neurotransmitters
Neurotransmitter
Acetycholine
Norepinephrine
Serotonin
Dopamine
Normal
Function
Disorder Associated
with Malfunctioning
Movement,
memory
Sleep, learning,
mood
Mood, appetite,
aggression
Movement,
reward
Alzheimer’s disease
GABA
Movement
Glutamate
Memory
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Depression
Depression
Parkinson’s disease:
schizophrenia
Huntington’s disease;
epilepsy
Neuron loss after
stroke
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Agonists and Antagonists
• Agonist – mimics neurotransmitter
action
• Antagonist – opposes action of a
neurotransmitter
• 9 that have been carefully studied.
• Let’s talk about a few on the next slide.
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Alcohol example
• Alcohol increases the activity of
gamma-aminobutyric acid (GABA), a
major inhibitory neurotransmitter.
• Alcohol decreases the activity of
glutamate, major excitatory
neurotransmitter.
• = substantial reduction in neural firing
within the brain.
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4) How Is the Nervous System
Organized?
1) Central Nervous System – Neurons in the
brain and spinal cord.
2) Peripheral Nervous System – Neurons in
the rest of the body
a) Somatic Nervous System- all the
neurons that take in sensory information
(touch and pain) from the body and
deliver it to the spinal cord and brain.
b) Autonomic Nervous System
i. Sympathtic Nervous SystemControls fight or flight function
ii. Parasympathetic Nervous SystemControls digestive and other
organ
function.
Somatic Nervous System
• Sends sensory information to central
nervous system for processing
• Sends messages from central nervous
system to muscles to direct motion
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Autonomic Nervous System
• Controls activities that are generally
autonomous or independent of one’s control
• Two subsystems
– Sympathetic Nervous System: Mobilizes the
body for action in face of stress
• “Fight or flight” response
– Parasympathetic Nervous System: Regulates
the body’s functions to conserve energy
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http://faculty.washington.edu/chudler/
auto.html
• Sympathetic
• Involved in states of
Arousal
• Involved in states of
calm
• Parasympathetic
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Figure 3.5
Figure 3.5 Organization of the human nervous system. This overview of the human nervous system shows the relationships
of its various parts and systems. The brain is traditionally divided into three regions: the hindbrain, the midbrain, and the
forebrain. The reticular formation runs through both the midbrain and the hindbrain on its way up and down the brainstem.
These and other parts of the brain are discussed in detail later in the chapter. The peripheral nervous system is made up of the
somatic nervous system, which controls voluntary muscles and sensory receptors, and the autonomic nervous system, which
controls the involuntary activities of smooth muscles, blood vessels, and glands.
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5) Structures of the Brain
 Brain Stem
 Pons, reticular formation,
cerebellum
 Midbrain
 Thalamus, hypothalamus,
hippocampus, substantia
nigra, pituitary gland
 Cerebral Cortex
 Visual, auditory, motor,
sensory
Brainstem
• Function
– regulates basic life functions.
• Location
– connects brain to the rest of the body via the spinal cord.
• Parts of Brainstem
– Reticular formation- regulates sleep/wake cycle
• Main source of the neurotransmitter Serotonin-important for
mood and activity levels.
– Pons• Main source of the neurotransmitter norepinephrine- important
for arousal and attention.
– Medulla- regulates heartbeat, breathing, swallowing, and
coughing.
Cerebellum
• Function
– Controls motor movement and balance
– Helpful in learning things that involve
movement (e.g. walking or skiing).
• Location
– Sits at the back of the brain and is
connected to the brain stem.
The Midbrain
• Controls certain types of automatic behaviors
that integrate simple movements with sensory
input
• Substantia nigra and the striatum are
involved in the smooth initiation
of movement
• (Amygdala; hippocampus; hypothalamus ->
also Limbic system
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Figure 3.14
Major Structures of the Forebrain
The Limbic System
Saul Kassin, Psychology. Copyright © 1995 by Houghton Mifflin Company. Reprinted by permission.
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Neocortex
• Location - Top wrinkly part
of the brain.
• Different Parts
– Frontal Lobe (front of brain) higher intellectual thinking
• Broca’s area- speech production
• Prefrontal cortex- working memory,
morality, mood
– Occipital Lobe (back of brain)vision
– Temporal Lobe (sides of brain)hearing, language, learning, and
memory
• Wenicke’s area- language
comprehension
Neocortex Cont.
– Parietal Lobe (top of brain)perception of touch
• Somatosensory stripcontains neurons that
register the sensation of
touch.
Figure 3.18
The Brain’s
Left and Right
Hemispheres
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Right Brain/Left Brain: Cerebral Specialization
• Each hemisphere specialized for
handling certain types of cognitive
tasks better than others
• Left hemisphere – verbal processing:
language, speech, reading, writing
• Right hemisphere – nonverbal
processing: spatial, musical, visual
recognition
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The Cerebrum: Two Hemispheres, Four Lobes
• Cerebral Hemispheres – two specialized
halves connected by the corpus collosum
• Four Lobes:
–
–
–
–
Occipital – vision
Parietal – somatosensory
Temporal – auditory
Frontal – movement, executive control systems
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Figure 3.14
Figure 3.14 The cerebral cortex in humans. The cerebral cortex consists of right and left halves, called cerebral
hemispheres. This diagram provides a view of the right hemisphere. Each cerebral hemisphere is divided into four
lobes (which are highlighted in the bottom inset): the occipital lobe, the parietal lobe, the temporal lobe, and the
frontal lobe. Each lobe has areas that handle particular functions, such as visual processing. The functions of the
prefrontal cortex are something of a mystery, but they appear to include working memory and relational reasoning.
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Corpus Callosum
• Function
– Communicates information
from one side of the brain to
the other.
• Location
– Connects the two brain
hemispheres
6) Building the Brain How We
Develop
• During the 3rd week of
prenatal development,
the outer layer of the
embryo (called the
ectoderm) folds in on
itself to form the
neural tube.
Figure 3.15
Alzheimer’s
Disease
and Brain
Atrophy
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go back
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