sympathetic nervous system

Main Entry: sympathetic nervous system
Function: noun
: the part of the autonomic nervous system that is concerned especially with preparing the body to react tosituations of stress or emergency, that contains chiefly adrenergic fibers and tends to depress secretion, decrease the tone and contractility of smooth muscle, increase heart rate, and that consistsessentially of preganglionic fibers arising in the thoracic and upper lumbar parts of the spinal cord and passing through delicate white rami communicantes to ganglia located in a pair of sympatheticchains situated one on each side of the spinal column or to more peripheral ganglia or ganglionated plexuses and postganglionic fibers passing typically through gray rami communicantes to spinal nerveswith which they are distributed to various end organs called also sympathetic system; —compare PARASYMPATHETIC NERVOUS SYSTEM

sympathetic nervous system n.
The part of the autonomic nervous system originating in the thoracic and lumbar regions of the spinal cord that in general inhibits or opposes the physiological effects of the parasympathetic nervous system, as in tending to reduce digestive secretions or speed up the heart.