6-5. ORGANIZATION OF THE AUTONOMIC NERVOUS SYSTEM
The autonomic nervous system is divided into two divisions: the sympathetic and
the parasympathetic. Figure 6-3 illustrates this division.
Figure 6-3. Divisions of the autonomic nervous system.
a. Sympathetic Nervous System. The sympathetic nervous system is
frequently referred to as the adrenergic nervous system. Because of its transmitter
epinephrine, which is more commonly known by its trade name "Adrenalin," it prepares
the body for stress situations. Stimulation of the adrenergic nervous system has the
general effect of expending energy. When a person is scared, this system prepares the
body for the fight or flight response. In other words, it prepares the body to either fight
or run. More information on this important system will be provided later in this lesson.
b. Parasympathetic Nervous System. The parasympathetic nervous system
is usually referred to as the cholinergic nervous system. The cholinergic nervous
system is responsible for bringing the body back to normal after the fight or flight
response. The effects of the cholinergic nervous system are generally the opposite of
those produced by the adrenergic nervous system. More information on the cholinergic
nervous system will be provided later in this lesson.
Section III. THE SYMPATHETIC NERVOUS SYSTEM
6-6. INTRODUCTION TO THE SYMPATHETIC NERVOUS SYSTEM
You have already been told that the sympathetic nervous system is one
component of the autonomic nervous system. Although this system is essential for a
person in normal living, it is not crucial for a person to have this system if that individual
is in a controlled environment (no stress, excitement, change in temperature, and so
forth). Without the presence of this system, one's temperature would not adjust to the
environmental temperature, one's level of blood glucose would not increase during
times of stress, and one's resistance to fatigue would decrease.