Importance of the gerontology of elastic arteries in the development of essential hypertension.

After discussing the changes of elastic type vessels with age, several possibilities for the resetting of baroreceptors in elastic type vessels are proposed: (1) Short-term resetting. On the basis of the architecture of the wall of elastic type vessels and the physical behavior of tubes, a pressure control organ within the vessel wall is proposed, by which, due to change in contraction of the vascular smooth muscles, the stress of the baroreceptors is changed and with it their set point relative to the blood pressure. This change can occur within seconds. (2) Mid-term resetting. The wall of elastic type vessels thickens, after a prolonged forced increase of blood pressure, decreasing the ratio of radius to wall thickness. Since the wall stress is proportional to the ratio of radius to wall thickness and the baroreceptors depend on the wall stress, they will now regulate the blood pressure on an elevated level. This change will be accomplished within days or weeks. (3) Long-term resetting. With age the wall of elastic type vessels becomes stiffer. Due to the peculiar physical behavior of tubes, this means that the wall stress decreases at a given blood pressure. Therefore, to maintain the same mean blood pressure throughout life, the baroreceptors have to adjust to the continuously decreasing wall stress. If this does not occur, the blood pressure will rise. Actually, the calculated increase of proposed blood pressure due to the decreasing wall stress parallels the recorded increase in blood pressure with age of the general population.