autonomic division of nervous system

(redirected from divisio autonomica systematis nervosi peripherici)

au·to·no·mic di·vi·sion of ner·vous sys·tem

(aw'tō-nom'ik di-vizh'ŭn nĕr'vŭs sis'tĕm)
That part of the nervous system that represents the motor innervation of smooth muscle, cardiac muscle, and gland cells. It consists of two physiologically and anatomically distinct, mutually antagonistic components: the sympathetic and parasympathetic parts. In both of these parts the pathway of innervation consists of a synaptic sequence of two motor neurons, one of which lies in the spinal cord or brainstem as the presynaptic (preganglionic) neuron, the thin but myelinated axon of which (preganglionic [presynaptic] or B fiber) emerges with an outgoing spinal or cranial nerve and synapses with one or more of the postsynaptic (postganglionic or, more strictly, ganglionic) neurons comprising the autonomic ganglia; theunmyelinated postsynaptic fibers in turn innervate the smooth muscle, cardiac muscle, or gland cells. The presynaptic neurons of the sympathetic part lie in the intermediolateral cell column of the thoracic and upper two lumbar segments of the spinal gray matter; those of the parasympathetic part comprise the visceral motor (visceral efferent) nuclei of the brainstem as well as the lateral column of the second to fourth sacral segments of the spinal cord. The ganglia of the sympathetic part are the paravertebral ganglia of the sympathetic trunk and the lumbar and sacral prevertebral or collateral ganglia; those of the parasympathetic part lie either near the organ to be innervated or as intramural ganglia within the organ itself except in the head, where there are four discrete parasympathetic ganglia (ciliary, otic, pterygopalatine, and submandibular). Impulse transmission from presynaptic to postsynaptic neuron is mediated by acetylcholine in both the sympathetic and parasympathetic parts; transmission from the postsynaptic fiber to the visceral effector tissues is classically said to be by acetylcholine in the parasympathetic part and by noradrenalin in the sympathetic part; recent evidence suggests the existence of further noncholinergic, nonadrenergic classes of postsynaptic fibers.
Synonym(s): divisio autonomica systematis nervosi peripherici [TA] , autonomic nervous system.