BP is regulated by an integrated set of physiological control mechanisms.
Immediate control over the course of 10–20 s is produced
by feedback mechanisms which respond to pressure
changes sensed by the carotid and aortic baroreceptors in the
high-pressure systemic arterial system. Regulation over the
course of minutes to hours is the domain of the circulating volume
control mechanisms based around low-pressure receptors
in the atria and great veins. Signals from these receptors are
responsible for feedback control of anti-diuretic hormone and
atrial natriuretic factor release and also modulate the control
of renin release by the sympathetic nervous system. The
long-term control of BP is primarily effected through the renin–
angiotensin–aldosterone system (RAAS) controlling natriuresis
and consequent diuresis. The RAAS feedback loop has a very
high gain, that is to say, small changes in pressure elicit a vigorous
feedback response to return the BP to its set point.