The human cardiovascular model upon which RCVSIM is based includes three major components. The first component is a lumped parameter model of the pulsatile heart and circulation which may be implemented as an intact preparation, a heart-lung unit preparation designed for measuring cardiac function curves, or a systemic circulation preparation designed for measuring venous return curves. The second component is a short-term regulatory system model which includes an arterial baroreflex system, a cardiopulmonary baroreflex system, and a direct neural coupling mechanism between respiration and heart rate. The final component is a model of resting physiologic perturbations which includes respiration, autoregulation of local vascular beds (exogenous disturbance to systemic arterial resistance), and higher brain center activity impinging on the autonomic nervous system(1/f exogenous disturbance to heart rate).