Biological Basis of
Behavior
The Neuron
Dendrites
Cell Body/Soma
Axon
(blue represents
myelin sheathinsulation for
electrical impulse)
Axon Terminus/
Terminal Buttons
Neuron Firing

At rest, the neuron is in a state of resting potential

Signal is received by receptors on the dendrite

If the signal reaches the threshold an action potential is initiated

Once an action potential is initiated there is an all-or-nothing response (it fires or it doesn’t)

The action potential is an electrical impulse that travels down the axon

When the electrical impulse reaches the terminal buttons, neurotransmitters or chemical
messengers are released into the synapse the space between the sending neuron and the
receiving neuron

The neurotransmitters then bind with the receptors on the dendrite of the next neuron


Excitatory neurotransmitters keep the signal going

Inhibitory neurotransmitters stop the signal from continuing
Once the action potential has been sent, the neuron must go through a refractory period
a time of rest between impulses. During this time reuptake of neurotransmitters occurs
when they are brought back into the original sending neuron in preparation to be used
again.
Neurotransmitters

Chemical messengers that send a signal from one neuron to the
next

Remember! The signal through one neuron is due to electricity, signals
between neurons is due to chemicals
Neurotransmitters
Function
Too Much
Too Little
Acetylcholine
(Ach)
Enables muscle action,
memory, and learning
Seizures
Alzheimer's
Dopamine
Learning, movement,
attention, emotion
Schizophrenia
Parkinson’s disease,
tremors, depression when
paired with low serotonin
Serotonin
Mood, hunger, sleep,
arousal
Depression
Norepinephrine
Alertness and arousal
Depression
GABA
Major inhibitory
neurotransmitter
Seizures, tremors,
insomnia
Glutamate
Major excitatory
neurotransmitter, involved
in memory
Endorphins
Released in response to
pain
Oxytocin
Enables feelings of love
and bonding
Migraines and seizures
Maladaptive social
interactions; aggression
Drugs and Neurotransmitters


Agonist drugs
The place of and serve the same function as a neurotransmitter

Used when there is too little of a neurotransmitter present
Antagonist
Take the place of a neurotransmitter but interrupt its function

Used when there is too much of something
Divisions of the Nervous System
The Endocrine System

Closely associated with the nervous system

Contains glands that release hormones into the blood stream

Together with the nervous system maintains homeostasis our body’s
internal balance

Pituitary Gland- located in the base of the brain, known as the master
gland because it controls all the others

Adrenal Glands- top of kidneys, release epinephrine and norepinephrine
in response to stress to trigger the fight or flight response
Neurotransmitters vs. Hormones
Neurotransmitters
Hormones

Chemical messengers

Chemical messengers

Nervous system

Endocrine system

Released from terminal buttons on
the neuron into the synapse

Released from endocrine glands
into the blood stream

Work fast

Work slowly

Don’t stay around long

Stay around for a while
Studying the Brain
Electroencephalogram EEG
 Records
the brain’s electrical activity
 Electrodes
 Can
detect brain-wave activity
assess brain damage and epilepsy
Computer Tomography (CT or CAT
Scan)

Examines the brain by taking x-ray photographs

Uses radiation

Can diagnose brain damage, bleeding, and
stroke
Magnetic Resonance Imaging
(MRI)

Uses a magnetic field that detects the
movement of electrons

Produces a detailed image of the soft tissue in
the brain

Can show unique features or abnormalities in
brain tissue
Functional MRI (fMRI)

Taking images before and after being asked to
do a task

Can show where blood is flowing during specific
tasks or when eliciting specific emotion
Positron emission tomography (PET)

Shows functional areas of the brain by observing
the presence of radioactive glucose

Similar to fMRI can show what area of the brain
is functioning during a specific task or emotional
response
Organization of the Brain
Older Brain Structures



Brainstem

Medulla- heartbeat and breathing

Pons- coordinates movement

Reticular formation- controls arousal
Thalamus
Sensory control center, receives information from senses and sends it to
the higher brain regions for processing

Receives higher brain’s relies and directs the medulla and cerebellum
Cerebellum

Nonverbal learning and memory

Coordinates voluntary movement
Limbic System

Hippocampus



Relay center for conscious memory processing; “save button”
Amygdala

Emotional memory processing

Specifically linked to fear and aggression
Hypothalamus

Bodily maintenance

Hunger, thirst, body temperature, sexual behavior

Also linked to emotion and reward
Cerebral Cortex

External area of the
brain

Where advanced
thinking and planning
occurs

Where memories are
stored
Occipital Lobes

Responds to visual
stimuli

Interprets what is
being “seen”
Temporal Lobes

Hearing

Language processing

Memory
Frontal Lobes

Personality

Intelligence

Voluntary movement
(centered in the
motor cortex)
Parietal Lobes

Spatial location

Attention

Processes information
about body sensation
(somatosensory
cortex)
Association Cortex

Neurons that make up
about 75% of the
cortex

Integrate sensory and
motor information