A model of some short term mechanisms controlling systemic pressure

In this work we analyze the role of the reflex control of total systemic vascular capacity through an original mathematical model of the human cardiovascular system. The model includes the elastic and resistive properties of systemic and pulmonary arteries and veins, the dependence of cardiac output on atrial pressure, and the action of the carotid sinus baroreflex on both systemic resistance and heart rate as well as on systemic venous unstressed volume. The values of model feedback gains were assigned to simulate the results of some experiments performed on vagotomized animals in an open loop condition. The effect of the carotid sinus baroreflex on unstressed volume, cardiac output and arterial pressure is correctly reproduced by the model. Analysis of the interactions between the mechanisms involved in the short-term arterial pressure control demonstrates that a mechanism acting on systemic venous capacity may have a significant role in cardiovascular homeostasis. It may especially contribute to the regulation of arterial pressure by modulating central venous pressure, hence improving cardiac performance and buffering the effect of acute hemodynamic changes.