The vasomotor center (VMC) is a portion of the medulla oblongata. Together with the cardiovascular center and respiratory center, it regulates blood pressure. It also has a more minor role in other homeostatic processes. 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 and X both feed into the vasomotor centre and are themselves involved in the regulation of blood pressure.