Learning Unit 4
BIOLOGICAL FOUNDATIONS OF BEHAVIOR

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Module 2.1
Neurons:
The Body’s
Wiring

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Neuron

Neuron – Nerve cells – basic building
block of the nervous system

Specialized cells that transmit info.
throughout the body in the form of
electrical impulses

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Neuron
Neurogenesis

◦ The process of developing new neurons

Repairing the brain
◦ Human brains have limited capacity to replace, rewire, or repair

damaged neurons after stroke, head wound, blow to the head

◦ People may regain some, but rarely all, of function after such an
incident

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PARTS OF THE
NEURON
Cell body (AKA Soma)

Large egg-shaped structure that provides
fuel, manufactures chemicals, and
maintains the entire neuron in working
order

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Parts of the
Neuron
Dendrite

◦ Branch/root-like extensions that arise from
the cell body

◦ Has receptor sites that enable them to
receive neurotransmitters released from
other neurons.

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PARTS OF THE
NEURON (CONT’D)
Axon:

◦ A single thread-like structure that
extends/carries signals away from the
cell body to neighboring neurons,
organs, or muscles

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Parts of the Neuron
Myelin sheath

◦ Looks like separate tube-like segments composed of fatty material
that wraps around and insulates an axon

Formed by glial cells – small cells that act like glue to hold
neurons together.

“Glial” – Greek “glue”

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PARTS OF THE NEURON (CONT’D)
Terminal Buttons

◦ Located at extreme ends of the axon’s branches

◦ Miniature container that stores & releases chemicals called
neurotransmitters (used to communicate with neighboring cells)

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KINDS OF
NEURONS

Sensory Neurons– transmit information about the outside
world TO the spinal cord & brain.

Motor Neurons– transmit messages FROM the brain and
spinal cord to the muscles that control the movements of
your body.

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KINDS OF NEURONS

Interneurons AKA Associative Neurons – connect neurons
to neurons.

◦ Most common neuron in the nervous system.

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That took a
lot of nerve!

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Synapse
Infinitely small fluid-filled gap – Less than a millionth of an
inch wide

Exists between a terminal button and its adjacent body
organ (heart), muscles (head), or cell body/dendrite

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How Neurons
Communicate

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How Neurons Communicate
The resting potential is the electrical potential across the cell membrane of a neuron in its
resting state.

◦ The resting potential of a neuron is about -70 millivolts (mV).

When the cell is stimulated, sodium gates at the base of the axon open. Positively charged
sodium ions rush into the cell, which causes the area inside the cell membrane at the point of
excitation to become less negatively charged.

◦ This process is called depolarization.

An action potential is an abrupt change from a negative to a positive charge of a nerve cell, also
called a neural impulse.

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Neurotransmitters
• Neurotransmitters are chemical messengers

• Each type of neurotransmitter fits into only one kind of receptor site.

• Reuptake is the process by which neurotransmitters are reabsorbed by

the transmitting neurons.

• Other neurotransmitters may be broken down by enzymes.

• Neuromodulators are chemicals that either increase or decrease the

sensitivity of the receiving neuron to neurotransmitters.

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Antagonists

Drugs or chemicals that block the
actions of neurotransmitters by
occupying their receptor sites.

Prevent transmission of the
messages the neurotransmitter
carries.

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Agonists

Drugs or chemicals that enhance
the activity of neurotransmitters.

Increase the availability or
effectiveness of neurotransmitters
by binding to their receptor sites
and mimicking their actions.

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Neurotransmitters

Endorphins – “morphine within” natural, opiate-
like neurotransmitters linked to pain control and
pleasure.

◦ Runners high

◦ Indifference to pain that sometimes follows severe
injuries.

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Mirror Neurons
Neurons that fire both when an action is
performed and when the same action is
merely observed.

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Module 2.2
THE NERVOUS SYSTEM: YOUR BODY’S INFORMATION
SUPERHIGHWAY

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The Central Nervous System:
Your Body’s Master Control Unit (1 of 2)

The nervous system consists of two components:

• the central nervous system, composed of the brain
and spinal cord, and

• the peripheral nervous system.

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The Central Nervous System:
Your Body’s Master Control Unit (2 of 2)

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The Peripheral Nervous System:
Your Body’s Link to the Outside World
(1 of 2)

The peripheral nervous system (PNS) is the part of the
nervous system that connects the spinal cord and brain with
the sensory organs, muscles, and glands.

The PNS is divided into two parts:
◦ Somatic nervous system

◦ Autonomic nervous system (ANS)

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The Peripheral Nervous System:
Your Body’s Link to the Outside
World (2 of 2)

The ANS is composed of two divisions, or
branches, that have largely opposite effects:

◦ The sympathetic nervous system

◦ The parasympathetic nervous system

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Organization of the
Nervous System

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The Brainstem

➢Responsible for automatic survival functions

➢Functions occur without any conscious effort – our brain
processes most info. outside of our awareness

➢Brainstem begins where the spinal cord enters the skull and
swells slightly forming the medulla.

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Parts of the Brain: Hindbrain
The hindbrain is the lowest and, in evolutionary terms, oldest
part of the brain.

The hindbrain includes:
◦ Medulla

◦ Pons

◦ Cerebellum

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Hindbrain

• Medulla
• Located on top of the spinal cord

• Includes a group of cells that control vital
reflexes, such as respiration, heart rate,
and blood pressure

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Hindbrain

• Pons

• Functions as a bridge to
interconnect messages
between the spinal cord and
brain.

• Helps regulate states of sleep
& wakefulness

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Hindbrain

• Cerebellum – “Little Brain”

• Balance & Coordination

• Involved in coordinating motor movements but not
in initiating voluntary movements

• Processes sensory input & coordinates movement
output & balance

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Midbrain

• Lies above the hindbrain, connects nerve
pathways that connect the hindbrain with
the forebrain.

• Parts of the midbrain make up the
brainstem

• Reticular formation – neural network that
rises from the hindbrain & passes through
the midbrain to the thalamus in the
forebrain.

• Regulates attention, alertness, &
arousal

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Forebrain

• The forebrain is the largest and uppermost part of the
brain.

• The forebrain includes:

• Thalamus

• Basal ganglia

• Hypothalamus

• Limbic system

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Forebrain

• The largest part of the brain.

• Major structures include the thalamus, hypothalamus, limbic system, & cerebral
cortex.

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Forebrain: Limbic System

• Thalamus – (switchboard/relay station) involved in
receiving sensory information from all of the senses
except for smell.

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Forebrain: Limbic
System
• Hypothalamus – regulates many

motivational behaviors, eating, drinking,
sleep cycles, & sexual arousal, emotional
responses – fight & flight (bodily
response to stress), emotional states, &
aggressive behavior & the secretion of
hormones.

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Forebrain:
Limbic System

Amygdala – 2 almond-shaped neural
clusters located at the tip of the temporal
lobe, that influence aggression, fear &
processing of emotional memories.

• Plays a role in evaluating emotional
significance of stimuli & facial
expressions – particularly fear,
distress, or threat.

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Forebrain: Limbic
System

• Hippocampus – a curved structure
shaped like a sea horse, located in the
temporal lobe that is involved in
saving memories & putting them into
permanent storage in various parts of
the brain.

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Forebrain
•Cerebral Cortex – (Latin – “Cover”) – Wrinkled surface of brain

•Intricate covering of interconnected neural cells that forms a thin surface
layer over your cerebrum, the largest part of the forebrain which consists
of 2 large masses, the right & left cerebral hemispheres.
• Brain’s outer “bark” layer.

•Corpus Callosum – Latin “Thick Body” connects cerebral hemispheres &
share information.

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Forebrain
• Located in front part of brain

•Called the “Executive Center”

• Many functions

• voluntary motor movements, interpreting and performing emotional behaviors,
behaving normally in social situations, maintaining a healthy personality, paying
attention to things in the environment etc.

•Frontal lobes shrink as we age.

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Damage to the
Frontal Lobe
Phineas Gage

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Forebrain
Frontal Lobe
•Motor Cortex – Narrow strip of cortex
that’s located on the back edge of the
frontal lobe and extends down its side

•Involved in the initiation of all voluntary
movements
• Right side controls left

• Left side controls right

•Organization and function of motor
cortex

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Motor Cortex
Body parts that utilize precision control
or fine motor skills (fingers, tongue)
occupy the greatest amount of cortical
space.

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Forebrain
Parietal Lobes
oParietal Lobes –Processes sensory
information from body parts, touching,
locating positions of limbs, feeling
temperature & pain

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Forebrain
Parietal Lobes
Somatosensory cortex – narrow
strip of cortex located on the
front edge of the parietal lobe &
down it’s side.

◦ Processes sensory information
about touch, location of limbs,
pain & temperature.

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Cerebral Cortex –
Sensory Cortex
Stimulate 1 point on the top of this band of
tissue and the person may report being touched
on the shoulder, stimulate some point on the
side and the person may feel something on the
face.

The more sensitive a body region, the larger the
area of the sensory cortex devoted to it. Lips
project to a larger brain area than your toes

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Forebrain
Occipital Lobes
❖Occipital Lobe – Located at the back

of the brain. Involved in processing
visual information, which includes
seeing colors and perceiving and
recognizing objects, animals, &
people.

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Forebrain
Temporal Lobes
•Temporal Lobe – Receive &
process sensory information
from the ears, producing the
experience of hearing.
• Involved in hearing, speaking

coherently and
understanding verbal &
written material.

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Cortex
•Association Areas – areas of the cerebral
cortex that piece together sensory
information to form meaningful
perceptions of the world and perform
higher mental functions.

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OVERALL VIEW
OF THE CORTEX

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Module 2.4
METHODS OF STUDYING THE BRAIN

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Brain
Plasticity
➢Plasticity – the ability of the
brain to adapt itself after
trauma or surgical alteration.

➢Plasticity is strongest during
childhood.

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Electroencephalograph (EEG)

•Electrodes attached to scalp

•Records electrical activity in the brain.

•Measures electrical currents or brain waves.

•Often used to study sleep brain wave patterns & electrical
activity in brain of people with physical or psychological
disorders.

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CT (Computed Tomography) Scan AKA CAT
Scan (Computed Axial Tomography)

•Imaging technique in which a computer measures the
reflection of a narrow X-ray beam from various angles as it
passes through the brain or other bodily structures

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Positron Emission Tomography
Scan (PET Scan)

A visual display of brain activity that detects
where a radioactive form of glucose goes while
the brain performs a given task.

Observe which parts of the brain light up when
given different tasks.
◦ Red & yellow indicate high activity while blue &

green indicate lower levels of activity.

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Images from radiologyinfo.org

Magnetic Resonance
Imaging (MRI)
Technique uses magnetic fields and radio
waves to produce computer-generated
images that distinguish among different
types of soft tissue

Allows us to see the anatomy of the
brain.

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Functional MRI (fMRI)

Can reveal brain’s structure & functioning

Reveals blood flow and brain activity by comparing
successive MRI scans

Shows brain function – measures changes in activity of
specific neurons that are functioning during cognitive
tasks, such as thinking, listening, or reading.

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