Psychology: A Self-Teaching Guide

34 PSYCHOLOGY

On the other hand, when you pick up a pen you are using efferent nerves. Mes-

sages are being carried away from the brain.

(a) When a neuron releases neurotransmitters it is either said to “fire” or to.

(b) Nerves that move away from a source are called.

Answers: (a) depolarize; (b) efferent.

The Nervous System: The Body’s Communication

Network

Neurons are not, of course, scattered at random in the body. They are organized.

This organization is called the nervous system.The nervous system is the

body’s communication network. Its function is often compared to the country’s

telephone system or the Internet. The nervous system allows any part of the

body to be in contact with any other part of the body within a fraction of a

second.

The nervous system has two main divisions. These are the central nervous

systemand the peripheral nervous system.The central nervous system con-

sists of the brain and the spinal cord. The brain is the subject of the next section.

Let’s turn our attention to the peripheral nervous system.

This peripheral nervous system itself has two divisions. These are the auto-

nomic nervous systemand somatic nervous system.The word autonomicis

similar to the word automatic,and it does in fact have a similar meaning. The auto-

nomic nervous system is somewhat independent or self-moving. This means it

doesn’t always have to have instructions coming from the brain. Some of its activ-

ities are said to be involuntary.

(a) The two main divisions of the nervous system are the and

the.

(b) The two divisions of the peripheral nervous system are the and the

.

Answers: (a) central nervous system; peripheral nervous system; (b) autonomic nervous

system; somatic nervous system.

The autonomic nervous system is involved in the regulation of such bodily

processes as digestion, blood pressure, pulse, breathing, and internal temperature.

This system has two additional divisions. These are the sympathetic division

and the parasympathetic division.

The sympathetic division is active primarily when there is an increase in