Separation of responses of arteries and veins to sympathetic stimulation.

• The sympathetic innervation of the vascular tree consists of postganglionic fibers derived from the sympathetic ganglion cells in the cervical, thoracic, and lumbar regions of the sympathetic trunks. In most vascular beds the blood vessels receive their innervation from postganglionic nerves which accompany the main arterial vessels supplying the bed. Information is sparse, however, regarding the derivation of the sympathetic innervation of the individual vessels, i. e., the arteries, arterioles, and veins, making up the vascular tree. Kuntz sums up current knowledge regarding innervation of the peripheral vasculature with the statement "The peripheral vessels are supplied by sympathetic fibers that join them through the somatic nerves that lie in closest proximity to them." One would surmise from this that arteries and veins could be innervated by anatomically separate nerve trunks; however, physiological evidence confirming this is needed.