Chapter 3
BRAIN AND BEHAVIOR
Key Questions
 How do nerve cells operate and communicate?
 What are the functions of major parts of the nervous
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systems?
How is the brain organized and what do its higher
structure do?
Why are the brain’s association areas important?
What happens when they are injured?
What kinds of behaviors are controlled by the
subcortex?
Does the glandular system affect behavior?
In what ways do right-and left—handed individuals
differ?
How do biopsychologists study the brain?
Neuron and Its Parts
 Neuron: Individual nerve cell; 100 billion in brain
 Dendrites: Receive messages from other neurons
 Soma: Cell body; body of the neuron. Receives messages
and sends messages down axon
 Axon: Carries information away from the cell body
 Axon Terminals: Branches that link the dendrites and
somas of other neurons
Fig. 2.1 An example of
a neuron, or nerve cell,
showing several of its
important features. The
right foreground shows
a nerve cell fiber in
cross section, and the
upper left inset gives a
more realistic picture of
the shape of neurons.
The nerve impulse
usually travels from the
dendrites and soma to
the branching ends of
the axon. The neuron
shown here is a motor
neuron. Motor neurons
originate in the brain or
spinal cord and send
their axons to the
muscles or glands of the
body.
Fig. 2.2 Activity in an axon can be measured by placing electrical probes inside and outside the axon. (The
scale is exaggerated here. Such measurements require ultra-small electrodes, as described later in this
chapter.) At rest, the inside of an axon is about –60 to –70 millivolts, compared with the outside.
Electrochemical changes in a nerve cell generate an action potential. When positively charged sodium ions
(Na+) rush into the cell, its interior briefly becomes positive. This is the action potential. After the action
potential, an outward flow of positive potassium ions (K+) restores the negative charge inside the axon.
(See Figure 2.3 for further explanation.)
Fig. 2.5 A highly magnified view of the synapse shown in Fig. 2.1. Neurotransmitters are stored in tiny
sacs called synaptic vesicles. When a nerve impulse arrives at an axon terminal, the vesicles move to the
surface and release neurotransmitters. These transmitter molecules cross the synaptic gap to affect the
next neuron. The size of the gap is exaggerated here; it is actually only about one millionth of an inch.
Transmitter molecules vary in their effects: Some excite the next neuron and some inhibit its activity.
The Nerve Impulse
 Resting Potential: Electrical charge of an inactive
neuron
 Threshold: Trigger point for a neuron’s firing
 Action Potential: Nerve impulse
 Ion Channels: Axon membrane has these tiny holes
or tunnels
 Negative After-Potential: When a neuron is less
willing to fire
Fig. 2.3 The inside of an axon normally has a negative electrical charge. The fluid surrounding an axon is
normally positive. As an action potential passes along the axon, these charges reverse, so that the
interior of the axon briefly becomes positive.
Fig. 2.4 Cross-sectional views
of an axon. The right end of the
top axon is at rest, with a
negatively charged interior. An
action potential begins when
the ion channels open and
sodium ions (Na+) enter the
axon. In this drawing the action
potential would travel rapidly
along the axon, from left to
right. In the lower axon the
action potential has moved to
the right. After it passes,
potassium ions (K+) flow out of
the axon. This quickly renews
the negative charge inside the
axon, so it can fire again.
Sodium ions that enter the
axon during an action potential
are pumped back out more
slowly. Their removal restores
the original resting potential.
Animation: Neuron & Neural Impulse
 Animation
Synapses and Neurotransmitters
 Synapse: The microscopic space between two
neurons, over with messages pass
 Neurotransmitters: Chemicals that alter activity in
neurons; brain chemicals
Acetylcholine: Activates muscles
 Dopamine: Muscle control
 Serotonin: Mood and appetite control
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 Messages from one neuron to another pass over a
microscopic gap called a synapse
 Receptor Site: Areas on the surface of neurons and
other cells that are sensitive to neurotransmitters
Animation: Synaptic Transmission
 Animation
Neural Regulators
 Neuropeptides: Regulate activity of other neurons
 Enkephalins: Relieve pain and stress; similar to endorphins
 Endorphins: Released by pituitary gland; also help to relieve
pain
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Placebos raise endorphin levels
The Nervous System- Wired for Action
Nerves and Neurons
 Nerves: Large bundles of axons and dendrites
 Myelin: Fatty layer that coats some axons
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Multiple Sclerosis (MS) occurs when myelin layer is
destroyed; numbness, weakness, and paralysis occur
 Neurilemma: Thin layer of cells wrapped around
axons outside brain and spinal cord; forms a
tunnel that damaged fibers follow as they repair
themselves
Brain Grafts and Nerve Regeneration
 Transplanting brain tissue
The Nervous System
 Central Nervous System (CNS): Brain and spinal
cord
 Peripheral Nervous System: All parts of the
nervous system outside of the brain and spinal
cord
Somatic System: Carries messages to and from skeletal
muscles and sense organs; controls voluntary behavior
 Autonomic System: Serves internal organs and glands;
controls automatic functions such as heart rate and blood
pressure
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Two Divisions of the Autonomic System
 Sympathetic: Arouses body; emergency system
 Parasympathetic: Quiets body; most active after
an emotional event
Fig. 3-9 (a) Central and peripheral nervous systems. (b) Spinal nerves, cranial nerves, and the autonomic
nervous system.
Fig. 3-10 Subparts of the nervous system.
Fig. 3-11 Sympathetic
and parasympathetic
branches of the
autonomic nervous
system.
The Spinal Cord
 White matter: Areas where myelin is present
 Spinal Nerves: 31 of them; carry sensory and motor
messages to and from the spinal cord
 Cranial Nerves: 12 pairs that leave the brain directly;
also work to communicate messages
How is the Spinal Cord Related to Behavior?
 Reflex Arc: Simplest behavioral pattern; occurs when
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a stimulus provokes an automatic response
Sensory Neuron: Nerve cell that carries messages
from the senses toward the CNS
Connector Neuron: Nerve cell that links two others
Motor Neuron: Cell that carries commands from the
CNS to muscles and glands
Effector Cells: Cells capable of producing a response
Fig. 3-12 A simple sensorymotor (reflex) arc. A simple
reflex is set in motion by a
stimulus to the skin (or other
part of the body). The nerve
impulse travels to the spinal
cord and then back out to a
muscle, which contracts.
Reflexes provide an
“automatic” protective device
for the body.
Courtesy of Richard Haier, University of California, Irvine
3-14 In the images you see here, red, orange, and yellow indicate high consumption of glucose; green, blue,
and pink show areas of low glucose use. The PET scan of the brain on the left shows that a man who solved 11
out of 36 reasoning problems burned more glucose than the man on the right, who solved 33.
Brain Mapping
 Read article from CNN
Project
Cerebral Cortex
 Cerebral Cortex: Outer layer of the cerebrum;
contains 70% of neurons in CNS
 Cerebrum: Two large hemispheres that cover
upper part of the brain
 Corticalization: Increase in size and wrinkling
of the cortex
Split Brains
 Cerebral Hemispheres: Right and left halves of the
cerebrum
 Corpus Callosum: Bundle of fibers connecting cerebral
hemispheres
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Corpus Callosum is cut; done to control severe epilepsy (seizure
disorder)
Result: The person now has two brains in one body
This operation is rare and is often used as a last resort
Figure 3-15 Corpus Callosum
Fig. 3-16 Basic nerve
pathways of vision. Notice
that the left portion of each
eye connects only to the left
half of the brain; likewise, the
right portion of each eye
connects to the right brain.
When the corpus callosum is
cut, a “split brain” results.
Then visual information can
be directed to one
hemisphere or the other by
flashing it in the right or left
visual field as the person
stares straight ahead.
Right Brain/Left Brain
 About 95 percent of our left brain is used for language
 Left hemisphere better at math, judging time and
rhythm, and coordinating order of complex
movements
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Processes information sequentially and is involved with
analysis
 Right hemisphere good at perceptual skills, and at
expressing and detecting other’s emotions
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Processes information simultaneously and holistically
Fig. 3-17 If a circle is flashed to the left brain and a split-brain patient is asked to say what she or he saw, the circle
is easily named. The person can also pick out the circle by touching shapes with the right hand, out of sight under a
tabletop (shown semi-transparent in the drawing). However, the left hand will be unable to identify the shape. If a
triangle is flashed to the right brain, the person cannot say what was seen (speech is controlled by the left
hemisphere). The person will also be unable to identify the correct shape by touch with the right hand. Now,
however, the left hand will have no difficulty picking out the hidden triangle. Separate testing of each hemisphere
reveals distinct specializations, as listed above.
Corpus Callosum Cut
 Video
Central Cortex Lobes
 Occipital: Back of brain; vision center
 Parietal: Just above occipital; bodily sensations
such as touch, pain, and temperature
(somatosensory area)
 Temporal: Each side of the brain; auditory and
language centers
 Frontal: Movement, sense of smell, higher mental
functions
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Contains motor cortex; controls motor movement
The left and right
brain have different
information
processing styles.
The right brain gets
the big pattern; the
left focuses on
small details.
Brain Parts
 Worksheet
When the Brain Fails to Function Properly
 Association Cortex: Combine and process information
from the five senses
 Aphasia: Language disturbance resulting from brain
damage
 Broca’s Area: Related to language and speech
production
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If damaged, person knows what s/he wants to say but can’t say
the words
 Wernicke’s Area: Related to language comprehension;
in left temporal lobe
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If damaged, person has problems with meanings of words, NOT
pronunciation
When the Brain Fails to Function Properly (cont.)
 Agnosia: Inability to identify seen objects
 Facial Agnosia: Inability to perceive familiar faces
Brain Injury
 Brain Injury Worksheet
His and Her Brains
 Read page 66
Hindbrain (Subcortex)
 Immediately below cerebral hemispheres
 Brainstem : Consists mainly of medulla and cerebellum
 Medulla: Controls vital life functions such as heart rate,
swallowing, and breathing
 Pons (Bridge): Acts as a bridge between medulla and
other structures
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Influences sleep and arousal
Cerebellum: Located at base of brain
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Regulates posture, muscle tone, and muscular coordination
Fig.3-22 This simplified drawing shows the main structures of the human brain and describes some of their
most important features. (You can use the color code in the foreground to identify which areas are part of the
forebrain, midbrain, and hindbrain.)
Hindbrain (Subcortex):
Reticular Formation (RF)
 Reticular Formation (RF): Inside medulla and
brainstem
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Associated with alertness, attention, and some reflexes
(breathing, coughing, sneezing, vomiting)
Reticular Activating System (RAS): Part of RF that keeps it
active and alert
RAS acts like the brain’s alarm clock
 Activates and arouses cerebral cortex
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Forebrain
 Structures are part of Limbic System: System
within forebrain closely linked to emotional
response and motivating behavior
Thalamus: Relays sensory information on the way to the
cortex; switchboard
 Hypothalamus: Regulates emotional behaviors and
motives (e.g., sex, hunger, rage, hormone release)
 Amygdala: Associated with fear responses
 Hippocampus: Associated with storing permanent
memories; helps us navigate through space
 Electrical stimulation of the brain (ESB): Is the direct
electrical stimulation and activation of the brain tissue
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Fig. 3-23 Parts of the
limbic system are
shown in this highly
simplified drawing.
Although only one side
is shown, the
hippocampus and the
amygdala extend out
into the temporal lobes
at each side of the
brain. The limbic
system is a sort of
“primitive core” of the
brain strongly
associated with
emotion.
The Brain in PerspectiveBeyond the Biocomputer
 Endocrine system: Made up of glands that pour chemicals
directly into the bloodstream or lymph system
 Hormones: Chemicals in blood that are carried throughout
the body that affect internal activities and behavior.
Endocrine System
 Glands that pour chemicals (hormones) directly
into the bloodstream or lymph system
 Pituitary Gland: Master gland that regulates
growth via growth hormone
 Too little means person will be smaller than
average
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Hypopituitary Dwarfs: As adults, perfectly proportioned
but tiny
Treatable by using human or synthetic growth hormone; will add a
few inches
 Treatment is long and expensive
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Endocrine System (cont.)
 Too much growth hormone leads to giantism
 Excessive body growth
 Acromegaly: Enlargement of arms, hands, feet, and
facial bones
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Caused by too much growth hormone secreted late in
growth period
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Andre the Giant
 Pituitary also governs functioning of other glands,
especially thyroid, adrenals, and gonads
PRINCESS BRIDE
Endocrine System (cont.)
 Pineal Gland: Regulates body rhythms and sleep
cycles.
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Releases hormone melatonin, which responds to daily
variations in light
 Thyroid: In neck; regulates metabolism
 Hyperthyroidism: Overactive thyroid; person tends to be
thin, tense, excitable, nervous
 Hypothyroidism: Underactive thyroid; person tends to be
inactive, sleepy, slow, obese
The Adrenal Glands
 Adrenals: Arouse body, regulate salt balance,
adjust body to stress, regulate sexual functioning;
located on top of kidneys
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Releases epinephrine and norepinephrine (also known as
adrenaline and noradrenaline)
Epinephrine arouses body; is associated with fear
 Norepinephrine arouses body; is linked with anger
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The Adrenal Glands (cont.)
 Adrenal Medulla: Inner core of adrenals; source of
epinephrine and norepinephrine
 Adrenal Cortex: Produces hormones known as corticoids
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Regulate salt balance
Deficiency in some types will cause powerful salt cravings
Also help body to adjust to stress
Secondary source of sex hormones
 Oversecretion of adrenal sex hormones can cause
virilism: exaggerated male characteristics (Bearded
woman)
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May also cause premature puberty if oversecretion occurs early in
life
Neurogenesis and Plasticity
 Neurogenesis: Production of new brain cells
 Plasticity: Brain’s ability to change its structure and
functions
Right or left?
 Read pages 75-78
Fig. 2.31 Neuroscientists are searching for
ways to repair damage caused by strokes and
other brain injuries. One promising technique
involves growing neurons in the laboratory
and injecting them into the brain. These
immature cells are placed near damaged
areas, where they can link up with healthy
neurons. The technique has proved
successful in animals and is now under study
in humans.
Fig. 2.27 A direct brain-computer link may provide a way of communicating for people who are paralyzed and unable
to speak. Activity in the patient’s motor cortex is detected by an implanted electrode. The signal is then amplified and
transmitted to a nearby computer. By thinking in certain ways, patients can move an on-screen cursor. This allows
them to spell out words or select from a list of messages, such as “I am thirsty.”
Researching the Brain
 Ablation: Surgical removal of parts of the brain
 Deep Lesioning: A thin wire electrode is lowered into
a specific area inside the brain; Electrical current is
then used to destroy a small amount of brain tissue
 Electrical Stimulation of the Brain (ESB): When an
electrode is used to activate target areas in the brain
 Electroencephalograph (EEG): Detects, amplifies, and
records electrical activity in the brain
Researching the Brain (cont.)
 Computed Tomographic Scanning (CT): Computer-
enhanced X-ray of the brain or body
 Magnetic Resonance Imaging (MRI): Uses a strong
magnetic field, not an X-ray, to produce an image of
the body’s interior
 Functional MRI: MRI that makes brain activity visible
 Positron Emission Tomography (PET): Computergenerated color image of brain activity, based on
glucose consumption in the brain
© Huntington Magnetic Resonance Center, Pasadena, California
An MRI scan of the brain.
Washington University School of Medicine, St.
Louis
PET scans.
Washington University School of Medicine, St. Louis
The bright spots you see here were created by a PET scan. However, here they have been placed over an
MRI scan so that the brain’s anatomy is visible. The three bright spots are areas in the left brain related to
language. The spot on the right is active during reading. The top-middle area is connected with speech. The
area to the left, in the frontal lobe is linked with thinking about a word’s meaning (Montgomery, 1989).
Fig. 2.10 The functions of brain structures are explored by selectively activating or removing them. Brain
research is often based on electrical stimulation, but chemical stimulation is also used at times.
Fig. 2.11 An EEG recording.
Brain Drain
 Great Brain Drain worksheet
Take Home Test!