Invitation to Psychology

122 Chapter 4 Neurons, Hormones, and the Brain

speeding motorcyclist, sympathetic nerves increase

your heart rate. Afterward, parasympathetic nerves

slow it down again and keep its rhythm regular.

Watch the Video Divisions of the Nervous

System at mypsychlab

parasympathetic system is more like a brake: It

tends to slow things down and keep them running

smoothly, enabling the body to conserve and store

energy. In everyday life, the two systems work in

harmony. If you have to jump out of the way of a

You are about to learn...

•    which cells function as the nervous system’s

communication specialists, and how they “talk”

to each other.

•    how cells once thought to be merely “glue” in

the brain have other important functions as well.

•    why researchers are excited about the discovery

of stem cells in the brain.

•    what happens when levels of neurotransmitters

are too low or too high.

•    which hormones are of special interest to

psychologists, and why.

•    which brain chemicals mimic the effects of mor-

phine by dulling pain and promoting pleasure.

Communication in the

Nervous System Lo 4.2

The blueprint we just described provides only

a general idea of the nervous system’s structure.

Now let’s turn to the details.

Your brain and other parts of the nervous

system contain two types of cells. Neurons, or nerve

cells, are the communication specialists, transmit-

ting information to, from, and within the central

nervous system. glia, or glial cells (from the Greek

word for “glue”), hold the neurons in place.

Glial cells used to get much less attention than

neurons, but we now know that these cells are much

more than just “glue.” They provide the neurons

glia [gLY-uh or
gLee-uh] Cells that
support, nurture, and
insulate neurons, remove
debris when neurons
die, enhance the forma-
tion and maintenance
of neural connections,
and modify neuronal
functioning.

neuron A cell that con-
ducts electrochemical
signals; the basic unit of
the nervous system; also
called a nerve cell.

Recite & Review

Recite: Put your nervous system into high gear by saying out loud everything you can remember

about the central, peripheral, somatic, autonomic, sympathetic, and parasympathetic nervous

systems.

Review: Next, go back and read this section again.

Now take this Quick Quiz by mentally filling in the missing parts of the nervous

system “house.” and be sure, once more, that you can describe what each part does.

Study and Review at mypsychlab

• peripheral: trans2. central: processes, interprets, and stores information and issues orders to muscles, glands, and organs1.

spinal cord: serves as a bridge between the brain and the peripheral nervous system, 3. mits information to and from the CNS

sympathetic: mobilizes the body for action, energy output5. somatic: controls the skeletal muscles4. produces reflexes

parasympathetic: conserves energy, maintains the body in a quiet state 6.

Brain

Nervous

System

Autonomic

Nervous

System

Nervous

System

6.?

Nervous

System

1.?

Nervous

System

5.?

Nervous

System

3.? 4.?

Nervous

System

2.?

Answers: