The Autonomic Nervous System Controls
the Activities of Smooth Muscle, Cardiac
Muscle, and Glands 208
• The autonomic nervous system (ANS), as shown, regulates
involuntary functions that are vital to life. It consists of the
sympathetic division and the parasympathetic division.
Autonomic nervous system—sympathetic division • Figure 7.14
Effectors: glands, cardiac
muscle (in the heart), and
smooth muscle (mainly in
the walls of blood vessels)
' t r
• The motor nerves of the autonomic nervous system usually
consist of a preganglionic neuron that releases acetylcholine
and a postganglionic neuron that releases the neurotrans-
mitters epinephrine or norepinephrine (sympathetic) or
acetylcholine (parasympathetic) to the effector cells
(cardiac muscle, smooth muscle, or glands).
• Because of the use of different neurotransmitters, the
sympathetic and parasympathetic divisions have opposite
effects. The sympathetic division produces “fight-or-flight”
responses in target organs, while the parasympathetic divi-
sion produces “rest-and-digest” responses.