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Chapter Four
Biology
Of
Behavior
By Courtney Graul
Now for the stuff we all know and
love… the brain’s components and how
they affect us.
The brain has two primary
responsibilities:
1)control of behavior
2)regulation of our body’s
physiological functions
In order for us to
understand how the brain
carries out these to main
functions we need to
understand how the brain
itself works.
Two Important Divisions
The Central
Nervous
System
The Peripheral
 Brain and spinal Nervous
cord
System
 Cranial and
spinal nerves
Central Nervous System
Three main structures of the brain:
1) Brain stem
2) Cerebellum
3) Cerebral hemispheres
Cells of the Nervous System

Neurons (nerve
cells) - the parts of
the nervous system
that bring sensory
information to the
brain, store
memories, reach
decisions, and
control the activities
of muscles

Glial cells – found in
the CNS and
provide support for
neurons and
supplies them with
needed chemicals
Principal Parts of a Neuron
– or cell body, contains
mechanisms that controls
metabolism and maintenance
of the cell. The soma also
receives messages from
other neurons.
Soma
Principal Parts of a Neuron
Dendrites – branch
from the soma to
receive messages from
other neurons and
transmit that
information to the
soma.
 Axon – (nerve fiber)
carries messages
away from the soma
toward the cells the
neuron is
communicating with
=action potential


Terminal button –
rounded swelling at
the end of the axon
of a neuron;
releases transmitter
substance
The Action potential
message carried by the axon –
a quick reversal in the electrical
charge of the axon, causing the
release of transmitter substance.
 The
 The
outside of the membrane is
positively charged (and the inside is
negatively charged) because the
axon contains ions. When the axon
is resting, its ion channels are
closed, so ions cannot move in or
out of the axon. An action potential
is caused by the opening of some
ion channels in the membrane at the
end of the axon nearest the soma.

Ion – a positively or
negatively charged
particle; produced
when many
substances dissolve
in water

Ion channel – a
special protein
molecule located in
the membrane of a
cell; controls the
entry or exit of
particular ions.
Communication
Neurons
can communicate with
the help of synapses.
Synapse – the junction between
the terminal button of one
neuron and the membrane of a
muscle fiber, a gland, or another
neuron.
Types of Neurons

Presynaptic Neurona neuron whose
terminal buttons
form synapses with
and excite or inhibit
another neuron.

Postsynaptic
Neuron – a neuron
with which the
terminal buttons of
another neuron form
synapses and that is
excited or inhibited
by that neuron.
Types of Neurons

Motor neurons – a
neuron whose
terminal buttons
form synapses with
muscle fibers.
When an action
potential travels
down its axon, the
associated muscle
fibers will twitch.

Sensory neuron –
detects changes in
the external or
internal environment
and sends
information about
these changes to
the central nervous
system.
Regions of Primary Sensory
and Motor Cortex
 Three
areas of the cerebral cortex
receive information from sensory
organs:
1)primary visual cortex – receives visual
information and is located in occipital
lobes
2)primary auditory cortex – receives
auditory information and is located in
the temporal lobes
somatosensory cortex –
receives information directly from
the somatosensory system (touch,
pleasure, vibration, pain, and
temperature); and is located in the
front part of the parietal lobes
 Primary
 The
three regions of primary
sensory cortex in each hemisphere
receive information from the
opposite side of the body. These
connections between the sensory
organs and the cerebral cortex are
said to be contralateral.
Various areas of the brain:
motor cortex – directly
controls the movements of the body,
located in the back part of the frontal
lobes.
 Frontal lobe – The front portion of the
cerebral cortex, including Broca’s
speech area and the motor cortex;
damage impairs movement, planning
and flexibility in behavioral strategies.
 Primary
lobe – located in the
cerebral cortex behind the frontal
lobe and above the temporal lobe;
contains the somatosensory cortex;
is involved in spatial perception and
memory.
 Parietal
lobe – the portion of the
cerebral cortex below the frontal
and parietal lobes and containing
the auditory cortex.
 Temporal
lobe – the rearmost portion of
the cerebral cortex; contains the primary
visual cortex.
 Sensory association cortex – receives
information from the primary sensory
areas.
 Motor association cortex – those
regions of the cerebral cortex that
control the primary motor cortex;
involved in planning and executing
behaviors.
 Occipital
More vocabulary
callosum – a large bundle of
axons that connects the cortex of the
two cerebral hemispheres.
 Corpus
– the process by which
important physiological characteristics
are regulated so they remain at their
optimum level.
 Homeostasis
The Brain Stem
 The
brain is made up of three main
structures including:
1)medulla – closest to the spinal cord;
controls vital functions such as heart
rate and blood pressure.
2)Pons – just anterior to the medulla;
involved in the control of sleep.
The Brain Stem
– just anterior to the pons;
involved in control of fighting and sexual
behavior (and decreased sensitivity to
pain during these behaviors).
 Midbrain
Cerebellum
 Plays
an important role in the control of
movement.
 Monitors information concerning posture
and balance and produces eye
movements that correlate with changes
in the position of the head.
 Damage to the cerebellum could result
in jerky, uncoordinated movements.
May also have difficulty speaking
because control of speech muscles
muscles may have been affected.
Structures within the Cerebral
Hemispheres
– all sensory information
except olfactory information is sent here
and then relayed to the cerebral cortex.
 Hypothalamus – located just above the
pituitary gland; controls the autonomic
nervous system and many behaviors
related to regulation and survival, such
as eating, drinking, fighting, shivering,
and sweating.
 Thalamus
Nervous System – the
portion of the peripheral nervous system
that controls the functions of the glands
and internal organs.
 Autonomic
branch – portion of the
ANS that activates functions that
accompany arousal and expenditure of
energy.
 Sympathetic
Nervous System –
The portion of the ANS that activates
functions that occur during a relaxed
state (such as digestion of food).
 Limbic system – a set of interconnected
structures of the brain important in
emotional and species-typical behavior;
includes the amygdala, hippocampus,
and limbic cortex.
 Parasympathetic
– part of the limbic system of
the brain located deep in the temporal
lobe; damage causes changes in
emotional and aggressive behavior.
 Amygdala
– also a part of the limbic
system, located in the temporal lobe;
plays important role in learning.
 Hippocampus
DRUGS
 Drugs
can affect the release or
production of transmitters substances.
 Drugs can mimic the effects of
transmitter substances on receptor
molecules, block these effects, or
interfere with the reuptake of a
transmitter substance once it has been
released. These changes can alter
perceptions, thoughts, and behaviors
controlled by certain transmitters
substances.
Barbiturates
 This
is a drug that causes sedation by
depressing the brain’s activity by
stimulating a certain category of
neuromodulator receptors.
 In
low doses can have a calming effect,
but as the dose increases may produce
difficulty in walking, talking, may lead to
unconsciousness, coma, and death.
 Abused
by people searching for
something to calm them.
 Sometimes
prescribed as sleep
medications, but they have serious
downfalls such as:
-inhibit or suppress dreaming
-produce unrefreshing sleep
-a dose prescribed to allow sleep is not
much lower than one causing death –
not very safe.
Benzodiazepine
 Many
antianxiety drugs belong to the
benzodiazepine family of drugs
 Includes Valium and Librium
 Are very effective at reducing anxiety
and are sometimes used to treat people
who are afflicted by periodic attacks of
severe anxiety
Cocaine and Amphetamine
 Both
inhibit the reuptake of dopamine
therefore strengthen the effectiveness
of synapses that use this transmitter
substance.
 The drugs mimic the effects of
reinforcing stimuli and cause many to
abuse them
 If
these drugs are taken over a period of
several days in large enough doses the
result could be symptoms of paranoid
schizophrenia.
 Those using the drugs regularly may
suffer from hallucinations and their
thoughts may be confused and difficult
to control.
The End