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sympathetic nervous system

(Science: anatomy, physiology) One of the two divisions of the vertebrate autonomic nervous system (the other being the parasympathetic nervous system).

The sympathetic preganglionic neurons have their cell bodies in the thoracic and lumbar regions of the spinal cord and connect to the paravertebral chain of sympathetic ganglia. Innervate heart and blood vessels, sweat glands, viscera and the adrenal medulla. most sympathetic neurons, but not all, use noradrenaline as a post ganglionic neurotransmitter. Originates in the thoracic regions of the spinal cord; opposes physiological effects of the parasympathetic: reduces digestive secretions; speeds the heart; contracts blood vessels.The part of the [[nervous system which takes over in 'fight or flight' circumstances where an immediate and effective response is required. The sympathetic nervous system works alongside the [[parasympathetic nervous system and is known as the involuntary system because the actions caused by it are not consciously executed.