Regulation of the Heart's Functions

If a regulating system consists of a mechanism for sensing the essential parameters, detecting deviations from a “set” value, and initiating corrective action, then the arterial pressure-regulating mechanism is the only regulating system described for the circulation in any detail. This mechanism appears to be important in maintaining a level of mean arterial pressure within a narrow range. It does not appear, however, to play a dominant role in adjusting the level of the circulation to meet spontaneously changing circulatory demands under many circumstances. During spontaneous activity by intact dogs, an increase in systolic ventricular pressure (and mean arterial pressure) is frequently accompanied by tachycardia as though some other mechanism were overriding the pressoreceptor mechanism. Thus, it appears that the circulatory system as a whole is largely controlled by neural mechanisms, usually initiated by higher levels of the nervous system. Very little is known of the sensory limbs of reflex arcs that can serve to regulate the cardiovascular system as a whole.