9-3. CHEMICAL TRANSMISSION IN THE CHOLINERGIC (PARASYMPATHETIC)
The chemical transmitter at both the preganglionic synapse and at the effector
organ is acetylcholine. Transmission of impulses is terminated by the destruction of
acetylcholine by the enzyme acetylcholinesterase.
9-4. EFFECTS PRODUCED BY THE CHOLINERGIC NERVOUS SYSTEM
The general effects of parasympathetic stimulation are conservation and
restoration of energy. The specific effects of the cholinergic nervous system are listed
a. Eye (Pupil). Contraction of the pupil (miosis) is produced by cholinergic
b. Heart. A decrease in the heart rate and a slight increase in the contraction
strength of the heart are cholinergic effects.
Bronchi. The bronchi are contracted by cholinergic stimulation.
d. Blood Vessels. The blood vessels of the skin and mucosa and skeletal
muscles are dilated by stimulation by the cholinergic nervous system.
e. Salivary Glands. Cholinergic stimulation of the salivary glands leads to
profuse, watery secretions.
f. Stomach. Cholinergic stimulation of the stomach leads to increased motility
and tone and relaxed (usually) sphincters.
g. Intestines. Increased intestinal motility and tone and stimulated secretion of
intestinal fluids are products of cholinergic stimulation.
h. Urinary Bladder. Contraction of the bladder wall and relaxation of the
sphincter are products of cholinergic stimulation. The result is that urination is
9-5. THERAPEUTIC USE OF CHOLINERGIC AGENTS
The cholinergic (parasympathomimetic) agents mimic the action of acetylcholine.
These drugs represent a relatively small class of therapeutic agents with very specific
clinical indications. For the most part, cholinergic agents are used in the treatment of
glaucoma (see lesson 5) and in the treatment of certain urinary tract disorders (they
help produce urination and the emptying of the bladder).