Psychology2016

60 CHAPTER 2

*involuntary: not under deliberate control.

Figure 2.7 The Peripheral Nervous System

Brain (CNS)

Nerves (PNS)

Spinal cord (CNS)

They are called “voluntary” because they can be moved at will

but are not limited to only that kind of movement.)

Involuntary* muscles, such as the heart, stomach, and

intestines, together with glands such as the adrenal glands and

the pancreas, are all controlled by clumps of neurons located on

or near the spinal column. (The words on or near are used quite

deliberately here. The neurons inside the spinal column are part of

the central nervous system, not the peripheral nervous system.)

These large groups of neurons near the spinal column make up

the autonomic nervous system.

THE AUTONOMIC NERVOUS SYSTEM The word autonomic

suggests that the functions of this system are more or less auto-

matic, which is basically correct. Whereas the somatic division

of the peripheral nervous system controls the senses and volun-

tary muscles, the autonomic division controls everything else in

the body—organs, glands, and involuntary muscles. The auto-

nomic nervous system is divided into two systems, the sympa-

thetic division and the parasympathetic division. (See Figure 2. 8 .)

(For a schematic representation of how all the various sections

of the nervous system are organized, look back at Figure 2.5.)

THE SYMPATHETIC DIVISION The sympathetic division of the

autonomic nervous system is primarily located on the middle

of the spinal column—running from near the top of the rib-

cage to the waist area. It may help to think of the name in these

sympathetic division
part of the ANS that is responsible
for reacting to stressful events and
Dodily arousal pfight-or-flight system.q

Figure 2.8 Functions of the Parasympathetic and Sympathetic Divisions of the Nervous System

bladderInhibits

contraction

Decrdigestiveeases

functions

of stomach,

pancrandeas,

intestines

Constricts

pupils andstimulates

tear glands

Slows

heart rate

Constricts bronchi

Incrdigestiveeases

functions

of stomach,pancreas,

and

intestines

Allows bladder

contraction

Parasympathetic Division Sympathetic Division

and inhibits tearDilates pupils

glands

Decrsalivationeases

Increases

heart rate

Dilates

bronchi

Increases

salivation

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