| 释义 |
DictionarySeeparasympathetic nervous systemparasympathetic nerve
par·a·sym·pa·thet·ic nerveone of the nerves of the parasympathetic nervous system.par·a·sym·pa·thet·ic nerve (par'ă-sim'pă-thet'ik nĕrv) One of the nerves of the parasympathetic nervous system. parasympathetic nerveA nerve composed of axons of the parasympathetic division of the autonomic nervous system. Parasympathetic innervation is always a chain of two consecutive axons. The first axon, the preganglionic parasympathetic axon, has its cell body in the brainstem or in the intermediate gray column of spinal cord segments S2–S4; the first axon leaves the brainstem through the oculomotor (CN III), facial (CN VII), glossopharyngeal (CN IX), or vagus (CN X) nerve, or it leaves the sacral spinal cord through a pelvic splanchnic nerve. The second axon in the chain, the postganglionic parasympathetic axon, has its cell body in a peripheral ganglion near its target tissue. The main transmitter used by both pre- and postganglionic parasympathetic axons is acetylcholine. In general, stimulation of parasympathetic nerves relaxes the body tone. See also: nerve |