Chapter 2
The Biological Basis of Behavior
 The brain is the control center of everything that we say and
 Complex organ
 Billons of cells
 Overlapping pathways and networks
 Plasticity= ability to adapt to new environmental
 Psychobiology= biological bases of behavior and mental
 Neuroscience= study of the brain and nervous system
 Neuropsychologists= study brain’s influence on
 Aka nerve cells
 Body contains approximately 100 billion
 Varies widely in size and shape
 Specialized to receive and transmit information
Neuron Types
 Sensory neurons= carry messages from sense organs to
the spinal cord or brain
 Motor neurons= carry messages from the spinal cord or
the brain to the muscles and glands
 Interneurons= carry messages from one neuron to
 Glial cells= hold neurons in place, provide nourishment,
remove waste, prevent harmful substances to passing into the
The Neural Impulse
 Yes-no, on-off electrochemical impulses
 Ions= electrically charged particles
 Resting Potential = electrical charge across a neuron
 Excess (+) ions on outside, (--) on the inside
 Neural Impulse= the firing of a nerve cell
 Polarization= a resting neuron; (--) on inside
 Depolarization= inflow of (+) sodium ions
 sets off a chain reaction
The Neural Impulse (cont)
 Threshold of Excitation= the level the impulse must
exceed to cause a neuron to fire
 All-or-none law= the neuron will fire or it won’t
 Absolute refractory period= time after a neuron has
fired that it WILL NOT fire not matter what the impulse
The Synapse
 Neurons are NOT connected
 Tiny space between called synaptic space
 Terminal button= end of axon branch
 Synaptic Vesicles = tiny sacs in terminal button that
release chemicals into the synapse
 Neurotransmitters= chemicals release by the synaptic
Neuron Toilet Worksheet
 Acetylcholine (Ach)= acts where neurons meet skeletal
 Role in arousal, attention, memory, & motivation
 Linked to Alzheimer’s disease
 Dopamine= assoc. with voluntary movement, learning,
memory & emotions
 Parkinson’s disease
 Serotonin= “mood molecule” (sets emotional tone)
 Half empty or half full
 Endorphins= turn down neurons that transmit pain messages
to the brain.
 **review chart on page 54**
 Imbalances have been linked to mental illness
 Schizophrenia (over abundance of dopamine)
 Depression (undersupply of serotonin & norepinephrine)
Nervous System Organization
 Includes the brain and the spinal cord
 Contains 90 % of the body’s neurons
 Peripheral Nervous System= division of the nervous
system that connects the CNS to the rest of the body
The Brain (cont.)
The Brain (cont.)
 Cerebellum= sense of balance and coordinating body’s
The Limbic System
The Limbic System is a
system of neural
structures at the border
of the brainstem and
cerebrum, associated
with emotions such as
fear, aggression and
drives for food and sex.
It includes the
hippocampus, amygdala,
and hypothalamus.
The Amygdala [ah-MIGdah-la] consists of two lima
bean-sized neural clusters
linked to the emotions of
fear and anger.
The Hypothalamus lies
below (hypo) the
thalamus. It directs
several maintenance
activities like eating,
drinking, body
temperature, and
control of emotions. It
helps govern the
endocrine system via
the pituitary gland.
The Brain (cont.)
 Midbrain= important for hearing and sight
 Pain is registered here (one of many)
 Thalamus= “relay station” for incoming messages from the
sense receptors (except for smell)
 Reticular Formation= ALERT system; network of neurons
 Pons- regulate sleep wake cycles
 Medulla= regulates respiration, heart rate, blood pressure