Part 1: cardiovascular responses to orthostatic stress and a valsalva maneuver. The auto-regulatory response is mediated by two sets of baroreceptors that are involved in the regulation of blood pressure and cardiac function. The arterial baroreceptors, which are found in the carotid sinus and the aortic arch are responsible for regulating heart rate and cardiac contractility through sympathetic and parasympathetic channels stemming from the cns. The other set of baroreceptors are the cardio-pulmonary baroreceptors, which are found in the right atrium, ventricles and pulmonary arteries. With slight decreases in blood pressure below normal values there is a venous pooling effect seen in the lower region of the body (hypovolemia) which causes a decrease in central venous pressure. This decrease in central venous pressure triggers the cardiopulmonary baroreflex to elicit a sympathetic mediated vasoconstrictor response in the muscles associated with an decrease in venous compliance and an increase in peripheral vascular resistance, allowing for greater venous return.