Mean arterial pressure is regulated by changes in cardiac output and systemic vascular resistance . The following scheme summarizes the factors that regulate cardiac output and systemic vascular resistance. Cardiac output is determined by the product of stroke volume and heart rate .
Stroke volume is determined by inotropy and preload .
The latter determines where the heart operates on the the Frank-Starling curve . Ventricular preload is altered by changes in venous compliance and blood volume. The latter is regulated by renal function, particularly renal handling of sodium and water. Heart rate, inotropy, venous compliance, and renal function are all strongly influenced by neurohumoral mechanisms . Furthermore, changes can occur in the relative number of parallel and series resistance elements.