parasympathetic (redirected from parasympathetic cholinergic vasodilator fibers)

parasympathetic /para·sym·pa·thet·ic/ (-sim″pah-thet´ik) see under system.

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par·a·sym·pa·thet·ic (pr-smp-thtk)

adj.

Of, relating to, or affecting the parasympathetic nervous system.

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para·sympa·theti·cal·ly adv.

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parasympathetic

[-sim′pəthet′ik]

Etymology: Gk, para + sympathein, to feel with

pertaining to the craniosacral division of the autonomic nervous system, consisting of the oculomotor, facial, glossopharyngeal, vagus, and pelvic nerves. The actions of the parasympathetic division are mediated by the release of acetylcholine and primarily involve the protection, conservation, and restoration of body resources. Preganglionic parasympathetic fibers, which emerge from the hypothalamus, other brain areas, and sacral segments of the spinal cord, form synapses in ganglia located near or in the walls of the organs to be innervated. Reactions to parasympathetic stimulation are highly localized and tend to counteract the adrenergic effects of sympathetic nerves. Parasympathetic fibers slow the heart; stimulate peristalsis; promote the secretion of lacrimal, salivary, and digestive glands; induce bile and insulin release; dilate peripheral and visceral blood vessels; constrict the pupils, esophagus, and bronchioles; and relax sphincters during micturition and defecation. Postganglionic parasympathetic fibers extend to the uterus, vagina, oviducts, and ovaries in females and to the prostate, seminal vesicles, and external genitalia in males, innervating blood vessels of pelvic organs in both sexes; stimulation of these nerves causes vasodilation in the clitoris and labia minora and erection of the penis.

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parasympathetic (par″sim″p-thet´ik),

adj pertaining to the part of the autonomic nervous system that controls craniosacral activity.

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parasympathetic

pertaining to the parasympathetic nervous system.

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parasympathetic cholinergic vasodilator fibers

cause dilatation of blood vessels in tissues including cerebral vessels, tongue, salivary glands, external genitalia, bladder, rectum.

parasympathetic nervous system

part of the autonomic nervous system, the preganglionic fibers of which leave the central nervous system with cranial nerves III, VII, IX and X and several sacral nerves (depending on species); postganglionic fibers are distributed to the heart, smooth muscles, and glands of the head and neck, and thoracic, abdominal and pelvic viscera. Almost three-quarters of all parasympathetic nerve fibers are in the vagus nerves, which serve both the thoracic and abdominal regions of the body.

The predominant secretion of the nerve endings of the parasympathetic nervous system is acetylcholine, which acts on the various organs of the body to either excite or inhibit certain activities. For example, stimulation of the parasympathetic system causes constriction of the pupil of the eye and contraction of the ciliary muscle; increase of the glandular secretion of enzymes, as in the case of the pancreas; increased peristalsis; and a slowed heart rate. Excitation of the sympathetic nervous system often results in an effect opposite to that of the parasympathetic system; however, most organs are predominantly under the control of either one or the other of the two nervous systems that compose the autonomic nervous system.

parasympathetic outflow

the total of parasympathetic nerves which leave the central nervous system. Includes the cranial and sacral outflows.

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parasympathetic

adjective Pertaining to the subdivision of the autonomic nervous system concerned with activities that, in general, inhibit or oppose the physiological effects of the sympathetic nervous system