A closed circulatory system model.

The model to be described is a “closed” system, comprised of four principal components : a pump, an arterial capacitance, a peripheral resistance, and a venous capacitance. The pump is servo-controlled, such that “cardiac output” is a function of venous pressure (FrankStarling mechanism). Also, because the model is a closed system, the venous pressure is a function of the cardiac output. The model therefore assists the student in gaining insight into the interrelationships between cardiac output and venous return. The student is able to construct “cardiac output” and “venous return’” curves, as described by Guyton (1,2), and to determine how these curves are affected by changes in a variety of circulatory variables, such as peripheral resistance, blood volume, and myocardial contractility.