Control of the coronary circulation during exercise.

Abstract

The cardiovascular response to exercise is typified by increases in heart rate, cardiac output, inotropic state of the cardiac chambers, whole body oxygen consumption, and blood flow to the active skeletal muscles. In most ani­ mals, some form of vasoconstriction occurs in the splanchnic region and inactive skeletal muscles. In the dog, splanchnic vasoconstriction does not occur; but contraction of the spleen does occur with exercise, and this increases the oxygen carrying capacity of the blood. The response of each organ system (e.g. heart, splanchnic organs, and skeletal muscle) is an eqUilibrium between the metabolic demand for oxygen by the organ and the neural control of organ blood flow exerted by the autonomic nervous sys­ tem. The efferent autonomic nervous system activity (principally sympa­ thetic nervous system) is increased during exercise to the heart, inactive skeletal muscle, and splanchnic region. The control of the coronary circulation during exercise appears to involve a combination of neural and metabolic events. Recent reviews have dealt with the metabolic control of the coronary circulation in great detail (5,40), so this topic is not covered extensively here. Other topics reviewed recently are cardiovascular adjustments during exercise (57), coronary vascular receptors (45), coronary reflexes (27), and control of coronary flow (29). With these reviews as background, the major focus here is the relationship between the increasing autonomic nervous system activity and the control of coronary blood flow during exercise. Recent publications suggest that, like the changes in organ blood flow to active and inactive regions of the body, the neural regulation of coronary blood flow may represent an impor­ tant component of the adjustment to exercise. The major role of the neural regulation of the coronary circulation during exercise may be to limit the