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.