Role of baroreceptor resetting in cardiovascular regulation: acute resetting.

Recent studies show that the arterial baroreceptor reflex cannot be defined by a single buffer curve. The reflex blood pressure and heart rate curves depend on the pressure to which the baroreceptors are exposed. If arterial pressure is elevated for longer than 3-5 min the threshold and the entire buffer curve are shifted to higher pressures. On the other hand, a reduced arterial pressure shifts the buffer curve to lower pressures. Part of this phenomenon, which has been called rapid or acute resetting, may be explained by changes in the baroreceptor discharge in response to exposure to sustained alterations in pressure. The reflex response, however, resets more than can be explained by changes in the baroreceptor discharge. A central component to the resetting process is suggested. Resetting allows the baroreceptor reflex to operate over a wide range of arterial pressures rather than being confined to a single range defined by one buffer curve. Resetting is not complete. That is, if the receptors are exposed to a change in pressure of 30 mm Hg the buffer curves shift by less than 30 mm Hg. Thus a signal concerning mean pressure is not eliminated by the resetting process.