cardiac output control. The circulatory system is provided with an extensive system for controlling
the arterial blood pressure. For instance, if at any time the pressure falls significantly below the normal
level of about 100 mm Hg, within seconds a barrage of nervous reflexes elicits a series of circulatory
changes to raise the pressure back toward normal. The nervous signals especially (a) increase the force
of heart pumping, (b) cause contraction of the large venous reservoirs to provide more blood to the
heart, and (c) cause generalized constriction of most of the arterioles throughoutthe body so that more
blood accumulates in the large arteries to increase the arterial pressure.
