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Chapter Overview
 Neural and Hormonal Systems
 Tools of Discovery and Older Brain Structures
 The Cerebral Cortex and Our Divided Brain
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Neural and Hormonal Systems: Biology,
Behavior, and Mind
 Everything psychological—every idea, every
mood, every urge—is biological.
 Psychologists working from a biological perspective
study the links between biology and behavior.
 Humans are biopsychosocial systems in which
biological, psychological, and social-cultural factors
interact to influence behavior.
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Neural and Hormonal Systems: Biology,
Behavior, and Mind
 Understanding of the relationship between
the brain and mind has evolved over time.
 Plato: Mine located in spherical head
 Aristotle: Mind found in heart
 Gall: Phrenology revealed mental abilities and
character traits
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A WRONGHEADED THEORY
Despite initial acceptance of Franz Gall’s speculations, bumps on the
skull tell us nothing about the brain’s underlying functions.
Nevertheless, some of his assumptions have held true. Though they
are not the functions Gall proposed, different parts of the brain do
control different aspects of behavior, as suggested here (from The
Human Brain Book).
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Neural and Hormonal Systems: Biology,
Behavior, and Mind
 During the past century, researchers
discovered
 Nerve cells conduct electricity and communicate
through chemical messages across tiny separating
gaps
 Specific brain systems serve specific functions and
information is integrated to construct a wide range of
experiences
 The adaptive brain is wired by experience
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Neuron’s Structure: Terms to Learn
 Neuron
 Refractory period
 Dendrites
 Threshold
 Axon
 All-or-none response
 Glial cells (glia)
 Neurotransmitters
 Synapse
 Reuptake
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Putting It All Together
Neurons are the elementary
components of the nervous
system—the body’s speedy
electrochemical system.
The neuron’s reaction is an all-ornone process.
Neurons receives signals through
branching dendrites and send
signals through its axons.
If a combined signal received by a
neuron exceed a minimum
threshold, the neuron fires,
transmitting an electrical impulse
down its axon through a chemicalto-electricity process.
Some axons are encased in a
myelin sheath, which enables
faster transmission.
Glial cells provide myelin and
support, nourish, and protect
neurons. These also play a role in
thinking and learning.
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Neurons and Neuronal Communication:
The Structure of a Neuron
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Action potential:
Neural impulse that travels down an axon
like a wave
2. This depolarization
produces another
action potential a little
farther along the
axon.
1. Neuron stimulation
causes a brief change in
electrical charge. If
strong enough, this
produces depolarization
and an action potential.
3. As the action potential
continues speedily down
the axon, the first section
has now completely
recharged.
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How Do Neurons Communicate With Each
The action
Other?
potential
travels down
the axon
from the cell
body to the
terminal
branches.
The neuron receives
signals from other
neurons; some are
telling it to fire and
some are telling it not
to fire.
When the threshold
is reached, the
action potential
starts moving. It
either fires or it does
not; more
stimulation does
nothing.(“all-ornone” response”).
2-3 How do nerve cells communicate with each other?
The signal is
transmitted
to another
cell but must
find a way to
cross a gap
(synapse)
between
cells.
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How Neurotransmitters Influence Behavior
 Neurotransmitters travel designated
pathways in the brain and may influence
specific behaviors and emotions.
 Acetylcloline (ACh) affects muscle action, learning
and memory.
 Endorphins are natural opiates released in response
to pain and exercise.
 Drugs and other chemicals affect brain chemistry at
synapses.
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How Drugs and Other Chemicals Alter
Neurotransmission
 Agonist: Molecule that increases a
neurotransmitter’s action.
 Antagonist: Molecule that inhibits or blocks a
neurotransmitter’s action.
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HOW NEUROTRANSMITTERS INFLUENCE US
Each of the brain’s differing chemical messengers has
designated pathways where it operates, as shown here for
serotonin and dopamine (Carter, 1998).
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Some Neurotransmitters and Their Functions
Neurotransmitter
Function
Examples of
Malfunctions
Acetylcholine (ACh)
Enables muscle action, learning, and memory
With Alzheimer’s disease, ACh producing neurons deteriorate.
Dopamine
Influences movement, learning, attention, and
emotion
Oversupply linked to schizophrenia.
Undersupply linked to tremors and loss
of motor control in Parkinson’s disease.
Serotonin
Affects mood, hunger, sleep, and arousal
Undersupply linked to depression.
Some drugs that raise serotonin levels
are used to treat depression.
Norepinephrine
Helps control alertness and arousal
Undersupply can depress mood.
GABA (gammaaminobutyricacid)
A major inhibitory neurotransmitter
Undersupply linked to seizures,
tremors, and insomnia.
Glutamate
A major excitatory neurotransmitter; involved in
memory
Oversupply can overstimulate the brain,
producing migraines or seizures (which
is why some people avoid MSG,
monosodium glutamate, in food).
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Neural and Hormonal Systems: The
Nervous System
 Nervous system
 Body’s speedy, electrochemical communication
network, consisting of all the nerve cells of the central
and peripheral nervous systems
 Central nervous system (CNS)
 Brain and spinal cord are body’s decision maker
 Peripheral nervous system (PNS)
 Sensory and motor neurons connecting the central nervous
system (CNS) to the rest of the body for gathering and
transmitting information
 Somatic nervous system and autonomic nervous system
2-5 What are the functions of the nervous system’s main divisions, and what are the
three main types of neurons?
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Autonomic nervous
system subdivisions
• Sympathetic subdivision
arouses and expends energy
and enables voluntary
control of skeletal muscles.
• Parasympathetic subdivision
calms and conserves energy,
allowing routine maintenance
activity and control
involuntary muscles and
glands.
The autonomic nervous system
arouses and calms
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Types of Neurons
 Neurons cluster into working networks and
include three types.
 Sensory neurons
 Carry messages from body’s tissues and sensory receptors
inward to your spinal cord and brain for processing.
 Motor neurons
 Carry instructions from your central nervous system out to
body’s muscles
 Interneurons within brain and spinal cord
 Communicate with one another and process information
between the sensory input and motor output
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The Central Nervous System
 Adult brain has about 86 billion neurons
(Azevedo et al., 2009).
 Brain accounts for about 2 percent of body
weight and uses 20 percent of energy.
 Neural networks and pathways govern reflexes
through highly efficient electrochemical
information system
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The Peripheral Nervous System
 Two parts with subdivisions
 Somatic nervous system
 Autonomic nervous system
 Sympathetic nervous system
 Parasympathetic nervous system
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The Functional Divisions of the Human
Nervous System
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A Simple Reflex
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The Endocrine System: Transmitting and
Interacting
Endocrine system is set of
glands that secrete
hormones into the
bloodstream.
In an intricate feedback
system, the brain’s
hypothalamus influences
the pituitary gland, which
influences other glands,
which release hormones and
influence the brain.
Hormones travel through the
body and affect other
tissues, including the brain.
The pituitary is the master
gland that influences
hormone release by other
glands, including the
adrenal glands.
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The Endocrine
System
FEEDBACK SYSTEM
• Brain → pituitary→ other
glands → hormones
→body and brain
• This reveals the interplay
between the nervous and
endocrine systems.
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Having Our Heads Examined
 Scientists can selectively destroy or
electrically, chemically, or magnetically
stimulate the brain.
 EEG (Electroencephalogram)
 PET (Positron emission tomography)
 MRI (Magnetic resonance imaging)
 fMRI (Functional MRI)
 Less complex brain in primitive vertebrates
handle basic survival functions.
 More complex brain in advanced mammals
(including humans) contain new brain
systems built on the old.
Stefan Klein/imagebroker/Alamy
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Older Brain Structure
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The Brainstem and Thalamus
The brainstem, including the medulla and pons, is an extension of
your spinal cord. The thalamus is attached to its top. The reticular
formation passes through both structures.
The Brainstem
THE BODY’S CROSSWIRING
Nerves from one side of the
brain are mostly linked to
the body’s opposite side.
Andrew Swift
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• Brainstem
• Is oldest and
innermost brain
region
• Medulla
• Is located at base
of the brainstem;
controls heartbeat
and breathing
• Pons
• Sits above medulla
and helps
coordinate
movement
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The Brain
 Reticular formation
 Involves nerve network running through the brainstem
and thalamus; plays an important role in controlling
arousal.
 Thalamus
 Is area at the top of the brainstem; directs sensory
messages to cortex and transmits replies to the
cerebellum and medulla
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The Cerebellum
 Aids in judgment of time, sound and texture
discrimination, and emotional control
 Coordinates voluntary movement and life-
sustaining functions
 Helps process and store information outside of
awareness
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The Limbic System
 This neural system sits between brain’s older parts and
its cerebral hemispheres
 Neural centers include
hippocampus, amygdala, and hypothalamus
 Is linked to emotions, memory, and drives
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The Limbic System
 Amygdala
 Consists of two lima-beansized neural clusters in the
limbic system; linked to
emotion.
 Hypothalamus
 Is neural structure lying
below the thalamus
 Directs several
maintenance activities
 Helps govern endocrine
system via the pituitary
gland, and is linked to
emotion and reward.
PAIN FOR PLEASURE This rat
has an electrode implanted in a reward
center of its hypothalamus. It will cross
an electric grid, accepting painful
shocks, in order to press a lever that
sends impulses to its reward center.
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New Ways of Using
Brain Stimulation
 Animal research
 Using brain
stimulation to control
animals’ actions in
search-and-rescue
operations
RATBOT ON A PLEASURE
CRUISE
Researchers used a remote
control brain stimulator to
guide rats across a field and
even up a tree.
 Human research
 Stimulating brain’s
reward circuits
 Reward deficiency
syndrome
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The Cerebral Cortex
CEREBRAL CORTEX
Two hemispheres
Each hemisphere has four lobes: Frontal, parietal, occipital, temporal
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Functions of the Cortex
 Motor cortex
 Fritsch and Hitzig: Discovered motor cortex at rear pf
frontal lobes
 Forester and Penfield: Mapped motor cortex and
discovered body areas requiring precise control and
mouth occupied most cortical space;
 Motor functions
 Electrically stimulating motor cortex can cause body
part movement
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Functions of the Motor Cortex
Left hemisphere tissue devoted to each body part in the motor cortex and the
somatosensory cortex
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The Cerebral Cortex: Brain-Computer
Interfaces
 Recording electrodes in monkey motor cortexes allowed
researchers to match brain signals with arm movements
and match brain signals with arm movements: mind
reading (Nicolelis, 2011)
 Follow-up experiments, both monkeys and humans have learned
to control a robot arm that could grasp and deliver food
(Collinger et al., 2013)
 Current clinical trials of cognitive neural prosthetics for
paralysis and amputation patients (Anderson et al.,
2010)
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BRAIN-COMPUTER INTERACTION
A patient with a severed spinal cord has electrodes planted in a
parietal lobe region involved with planning to reach out one’s
arm. The resulting signal can enable the patient to move a
robotic limb, stimulate muscles that activate a paralyzed limb,
navigate a wheelchair, control a TV, and use the Internet.
(Graphic adapted from Andersen et al., 2010.)
NeuroImage, Vol. 4, V.P. Clark, K. Keill, J. Ma. Maisog, S.
Courtney, L. G. Ungerleider, and J. V Magnetic Resonance
Imaging of Human
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Functions of the
Cortex
 Sensory functions
THE BRAIN IN ACTION
This fMRI (functional MRI) scan
shows the visual cortex in the
occipital lobes activated
(color represents increased
bloodflow) as a research
participant looks at a photo.
When the person stops looking,
the region instantly calms down.
 Somatosensory
cortex processes
information from skin
senses and body
parts movement
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Functions of the Cortex
 Sensory functions
 The visual cortex of the occipital lobes at the rear of
your brain receives input from your eyes.
 The auditory cortex, in your temporal lobes—above
your ears—receives information from your ears.
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Functions of the Cortex
 Association areas of the cortex
 Are found in all four lobes
 Found in the frontal lobes enable judgment, planning,
and processing of new memories
 Damage to association areas
 Result in different losses
Let’s take a closer look a one case.
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Collection of Jack and Beverly Wilgus
A BLAST FROM THE PAST
(a) Phineas Gage’s skull was kept as a medical record. Using
measurements and modern neuroimaging techniques, researchers
have reconstructed the probable path of the rod through Gage’s brain
(Van Horn et al., 2012).
(b) This recently discovered photo shows Gage after his accident.
(This image has been reversed to show the features correctly. Early
photos, including this one, were actually mirror images.)
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The Brain’s Plasticity
 Brain damage effects
 If one hemisphere is damaged early in life, other will
assume many function by reorganizing or building
new pathways.
 Plasticity diminishes later in life.
 Brain sometimes mends itself by forming new
neurons through neurogenesis
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The Cerebral Cortex and The Brain’s
Plasticity
 Constraint-induced therapy aims to rewire
brains and improve dexterity of brain-damaged
people
 Blindness or deafness make unused brain areas
available for other uses
 Similar reassignment occurs when disease or
damage frees up other brain areas normally
dedicated to specific functions
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THE CORPUS CALLOSUM
This large band of neural fibers connects the two brain hemispheres. To
photograph this half brain, a surgeon separated the hemispheres by
cutting through the corpus callosum and lower brain regions. The
high-resolution diffusion spectrum image on the right, showing a top
view, reveals brain neural networks within the two hemispheres, and the
corpus callosum neural bridge between them.
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Our Divided Brain
 Split brain hemisphere
 Isolated by cutting the fibers (mainly those of the corpus
callosum) connecting them
 Intact brain
 Data received by either hemisphere are quickly
transmitted to the other side, across the corpus
callosum.
 Severed corpus callosum brain
 This information sharing does not take place.
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Right-Left Differences in Intact Brains
 Each hemisphere performs distinct
functions. Humans have unified brains with
specialized parts.
 Left hemisphere is good at making quick, exact
interpretations of language.
 Right hemisphere excels in making inferences,
modulating speech, and facilitating self-awareness
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Handedness
 Nearly 90 percent of people are right-handed and
process speech primarily in left hemisphere.
 Universal prevalence of right-handers suggests a
genetic or prenatal influence.
 Left-handedness more likely to have reading
disabilities, allergies, and migraines BUT more
common among musicians, mathematicians, and
many athletes and artists.
 Pros and cons of left-handedness seem about
equal.