Hypotensive Drugs

Abstract

Based on a Dissertation read before the Royal Medical Society on Friday, 23rd October 1959.The arterial blood pressure is controlled by the autonomic nervous system. Information about the level of the arterial pressure is obtained by the stretch receptors of the aortic arch and the carotid sinus. An increase in pressure is registered as an increase in sensory discharge frequency and vice-versa. The sensory impulses reach the medulla by the carotid sinus nerves, the cardia-aortic nerves and the vagi. The central nervous mechanisms are such that changes in the arterial pressure evoke compensatory changes in the dynamics of the circulation. A fall in carotidsinus pressure, for example, evokes peripheral arteriolar constriction, an increase in venous tone and an increase in heart rate. Generalised arteriolar constriction increases total peripheral resistance. An increase in venous tone tends to increase the venous tilling pressure and the stroke volume of the heart. The combined increase in stroke volume and heart rate produces a rise in cardiac output, which, together with the increase in peripheral resistance,restores the original arterial pressure