Understanding Psychology (10th Ed)

R E C A P / E V A L U A T E / R E T H I N K
R E C A P
Why do psychologists study the brain and nervous system?
• A full understanding of human behavior requires knowl-
edge of the biological infl uences underlying that behav-
ior, especially those originating in the nervous system. 
Psychologists who specialize in studying the effects of 
biological structures and functions on behavior are 
known as behavioral neuroscientists. (p. 60) 
What are the basic elements of the nervous system?
• Neurons, the most basic elements of the nervous system, 
carry nerve impulses from one part of the body to an-
other. Information in a neuron generally follows a route 
that begins with the dendrites, continues into the cell 
body, and leads ultimately down the tubelike extension, 
the axon. (p. 61) 
How does the nervous system communicate electrical and 
chemical messages from one part to another?
• Most axons are insulated by a coating called the myelin 
sheath. When a neuron receives a message to fi re, it 
releases an action potential, an electric charge that travels 
through the axon. Neurons operate according to an 
all-or-none law: Either they are at rest, or an action 
potential is moving through them. There is no in-between 
state. (p. 62)
• Once a neuron fi res, nerve impulses are carried to other 
neurons through the production of chemical substances, 
neurotransmitters, that actually bridge the gaps—known 
as synapses—between neurons. Neurotransmitters may 
be either excitatory, telling other neurons to fi re, or 
inhibitory, preventing or decreasing the likelihood of 
other neurons fi ring. (p. 65)
• Endorphins, another type of neurotransmitter, are 
related to the reduction of pain. Endorphins aid in the 
production of a natural painkiller and are probably 
responsible for creating the kind of euphoria that joggers 
sometimes experience after running. (p. 68)