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parasympathetic nervous system
parasympathetic nervous systemn. The part of the autonomic nervous system originating in the brainstem and the lower part of the spinal cord that, in general, inhibits or opposes the physiological effects of the sympathetic nervous system, as in tending to stimulate digestive secretions, slow the heart, constrict the pupils, and dilate blood vessels.par·a·sym·pa·thet·ic nervous system (păr′ə-sĭm′pə-thĕt′ĭk) The part of the autonomic nervous system that tends to act in opposition to the sympathetic nervous system, as by slowing down the heart and dilating the blood vessels. It also regulates the function of many glands, such as those that produce tears and saliva.parasympathetic nervous systemThe part of the autonomic nervous system that controls rest and digestion.ThesaurusNoun | 1. | parasympathetic nervous system - originates in the brain stem and lower part of the spinal cord; opposes physiological effects of the sympathetic nervous system: stimulates digestive secretions; slows the heart; constricts the pupils; dilates blood vesselsparasympatheticnervous system, systema nervosum - the sensory and control apparatus consisting of a network of nerve cellsANS, autonomic nervous system - the part of the nervous system of vertebrates that controls involuntary actions of the smooth muscles and heart and glands | Translations
parasympathetic nervous system
parasympathetic nervous system: see nervous systemnervous system, network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system. ..... Click the link for more information. .Parasympathetic nervous system A portion of the autonomic system. It consists of two neuron chains, but differs from the sympathetic nervous system in that the first neuron has a long axon and synapses with the second neuron near or in the organ innervated. In general, its action is in opposition to that of the sympathetic nervous system, which is the other part of the autonomic system. It cannot be said that one system, the sympathetic, always has a excitatory role and the other, the parasympathetic, an inhibitory role; the situation depends on the organ in question. However, it may be said that the sympathetic system, by altering the level at which various organs function, enables the body to rise to emergency demands encountered in flight, combat, pursuit, and pain. The parasympathetic system appears to be in control during such pleasant periods as digestion and rest. The alkaloid pilocarpine excites parasympathetic activity while atropine inhibits it. See Autonomic nervous system, Sympathetic nervous system Parasympathetic Nervous System the part of the autonomic nervous system whose ganglia are located very close to or in the innervated organs. The centers of the parasympathetic nervous system are found in the mesencephalon and medulla oblongata and in the sacral part of the spinal cord. The fibers of the parasympathetic nervous system proceed to the viscera as part of the third (oculomotor), seventh (facial), ninth (glossopharyngeal), and especially the tenth (vagus) cranial nerves and as part of the pelvic nerve. In many cases, the parasympathetic and sympathetic nervous systems are directly opposed to one another in their effect on organs. Whereas sympathetic stimulation will act to accelerate and intensify heart contractions, raise the blood pressure, and dilate the pupils, parasympathetic stimulation will act to slow and weaken the heartbeat, lower arterial pressure, and contract the pupils. Efferent neurons of the parasympathetic nervous system are typically situated in the innervated organ proper and not in the separate trunk, as is the case in the sympathetic nervous system. The mediator substance formed in the nerve endings of the parasympathetic nervous system is acetylcholine; the predominant mediator substance in the sympathetic nervous system is norepinephrine. O. M. BENIUMOV parasympathetic nervous system[¦par·ə‚sim·pə′thed·ik ′nər·vəs ‚sis·təm] (neuroscience) The craniosacral portion of the autonomic nervous system, consisting of preganglionic nerve fibers in certain sacral and cranial nerves, outlying ganglia, and postganglionic fibers. parasympathetic nervous system
parasympathetic nervous system part of the autonomic nervous system" >autonomic nervous system, the preganglionic fibers of which leave the central nervous system with cranial nerves III, VII, IX, and X and the first three sacral nerves; postganglionic fibers are distributed to the heart, smooth muscles, and glands of the head and neck, and thoracic, abdominal, and pelvic viscera. (See also Color Plates.) Almost three-fourths of all parasympathetic nerve fibers are in the vagus nerves, which serve the entire thoracic and abdominal regions of the body. The predominant secretion of the nerve endings of the parasympathetic nervous system is acetylcholine, which acts on 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. It often happens that excitation of the sympathetic nervous system results in an effect opposite that of the parasympathetic system; however, most organs are under the almost exclusive control of either one or the otherof the two nervous systems that compose the autonomic nervous system.parasympathetic nervous systemn. The part of the autonomic nervous system originating in the brainstem and the lower part of the spinal cord that, in general, inhibits or opposes the physiological effects of the sympathetic nervous system, as in tending to stimulate digestive secretions, slow the heart, constrict the pupils, and dilate blood vessels.par·a·sym·pa·thet·ic ner·vous sys·tem (par'ă-sim'pă-thet'ik nĕr'vŭs sis'tĕm) The branch of the autonomic nervous system that sends motor signals to glandular smooth muscle, and cardiac tissue, during recovery from threat. Compare: sympathetic nervous systemparasympathetic nervous system One of the two divisions of the AUTONOMIC NERVOUS SYSTEM. The parasympathetic system leaves the central nervous system in the 3rd, 7th, 9th and 10th CRANIAL NERVES and from the 2nd to the 4th SACRAL segments of the spinal cord. Parasympathetic action constricts the pupils of the eyes, promotes salivation and tearing, slows the heart, constricts the BRONCHI, increases the activity of the intestines, contracts the bladder wall and relaxes the SPHINCTERS and promotes erection of the penis. See also SYMPATHETIC NERVOUS SYSTEM.Parasympathetic nervous systemThe division of the autonomic (involuntary or unwilled) nervous system that slows heart rate, increases digestive and gland activity, and relaxes the sphincter muscles that close off body organs.Mentioned in: Cholinergic Drugs, Sympathectomypar·a·sym·pa·thet·ic ner·vous sys·tem (par'ă-sim'pă-thet'ik nĕr'vŭs sis'tĕm) Branch of the autonomic nervous system that sends motor signals to glandular smooth muscle, and cardiac tissue, during recovery from threat. AcronymsSeePSNSparasympathetic nervous system
Synonyms for parasympathetic nervous systemnoun originates in the brain stem and lower part of the spinal cordSynonymsRelated Words- nervous system
- systema nervosum
- ANS
- autonomic nervous system
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