- Parasympathetic nervous system
- A part of nervous system that serves to slow the heart rate, increase the intestinal and gland activity, and relax the sphincter muscles. The parasympathetic nervous system, together with the sympathetic nervous system (that accelerates the heart rate, constricts blood vessels, and raises blood pressure), constitutes the autonomic nervous system.
* * *parasympathetic nervous system n the part of the autonomic nervous system that contains chiefly cholinergic fibers, that tends to induce secretion, to increase the tone and contractility of smooth muscle, and to slow the heart rate, and that consists of (1) a cranial part made up of preganglionic fibers leaving and passing the midbrain by the oculomotor nerves and the hindbrain by the facial, glossopharyngeal, vagus, and accessory nerves and passing to the ciliary, sphenopalatine, submandibular, and otic ganglia of the head or to ganglionated plexuses of the thorax and abdomen and postganglionic fibers passing from these ganglia to end organs of the head and upper trunk and (2) a sacral part made up of preganglionic fibers emerging and passing in the sacral nerves and passing to ganglionated plexuses of the lower trunk and postganglionic fibers passing from these plexuses chiefly to the viscera of the lower abdomen and the external genital organs called also parasympathetic system compare SYMPATHETIC NERVOUS SYSTEM
* * *the craniosacral division of the autonomic nervous system, its preganglionic fibers traveling with cranial nerves III, VII, IX, and X, and with the second to fourth sacral ventral roots; it innervates the heart, the smooth muscle and glands of the head and neck, and the thoracic, abdominal, and pelvic viscera. The ganglion cells with which these fibers synapse are in or near the organs innervated. In TA terminology, called pars parasympathica divisionis autonomici systematis nervosi. Called also craniosacral division and craniosacral part of autonomic nervous system. See Plate 42.
Medical dictionary. 2011.