What is "vasomotor center"

Vasomotor \Vas`o*mo"tor\, a. [L. vas a vessel + motor that which moves fr. movere to move.] (Physiol.) Causing movement in the walls of vessels; as, the vasomotor mechanisms; the vasomotor nerves, a system of nerves distributed over the muscular coats of the blood vessels.

Vasomotor center, the chief dominating or general center which supplies all the unstriped muscles of the arterial system with motor nerves, situated in a part of the medulla oblongata; a center of reflex action by the working of which afferent impulses are changed into efferent, -- vasomotor impulses leading either to dilation or constriction of the blood vessels.

The vasomotor center (VMC) is a portion of the medulla oblongata together with the cardiac center and respiratory center, that regulates blood pressure and other homeostatic processes. Vasomotor center is a fairly archaic term since this function relies not on a single brain structure ("center") but rather represents a presympathetic network of interacting neurons PMID 16760914. Upon increase in carbon dioxide level at central chemoreceptors, it stimulates the sympathetic system to constrict vessels. This is opposite to carbon dioxide in tissues causing vasodilatation, especially in the brain. Cranial nerves IX ( Glossopharyngeal nerve) and X Vagus nerve both feed into the vasomotor centre and are themselves involved in the regulation of blood pressure. The localization of VMC was determined by Filipp Ovsyannikov in 1871.