Vasoconstrictor systems supplying skeletal muscle, skin, and viscera.

Stimulation of afferent inputs from the body surface and from the interior of the body elicits distinct reflex patterns in post- and preganglionic vasoconstrictor neurons supplying skeletal muscle, skin and viscera of the cat. These patterns are due to characteristic organizations of the vasoconstrictor systems in the neuraxis and may serve as functional labels for the neurons but also as conceptual leads in experimental investigations of the vasoconstrictor systems in the neuraxis. These systems may be generally organized in a hierarchical manner. The lowest level of the hierarchy consists of separate common final sympathetic pathways, the pre-postganglionic channels, with some integrating processes in the ganglia. Then there is the spinal level with the spinal sympathetic motor units. Different functional motor units overlap and receive their inputs from the periphery via primary afferents and from brain stem and hypothalamus via spinal descending systems. Brain stem and hypothalamus organize spinal motor units into global functional units.