Autoregulation

Autoregulation is a process within many biological systems, resulting from some internal adaptive mechanism that works to adjust (or mitigate) the systems response to stimuli. While most systems of the body show some degree of autoregulation, it is most clearly observed in the kidney, the heart, and the brain. Perfusion of these organs (especially the latter two) is essential for life, and through autoregulation the body can divert blood (and thus, oxygen) where it is most needed.

Cerebral autoregulation
More so than most other organs, the brain is very sensitive to overperfusion, and cerebral autoregulation plays an important role in maintaining an appropriate blood pressure to that region. More detail is available at Cerebral perfusion pressure.

Homeometric autoregulation
Homeometric autoregulation, in the context of the circulatory system, is the heart's ability to increase contractility and restore stroke volume when afterload increases. This is in contrast to heterometric regulation.

Coronary circulatory autoregulation
Since the heart is a very aerobic organ, needing oxygen for the efficient production of ATP & Creatine Phosphate from fatty acids (and to a smaller extent, glucose & very little lactate), the coronary circulation is auto regulated so that the heart receives the right flow of blood & hence sufficient supply of oxygen. If a sufficient flow of oxygen is met and the resistance in the coronary circulation rises (perhaps due to vasoconstriction), then the coronary perfusion pressure (CPP) increases proportionally, to maintain the same flow. In this way, the same flow through the coronary circulation is maintained over a range of pressures. This part of coronary circulatory regulation is known as auto regulation and it occurs over a plateau, reflecting the constant blood flow at varying CPP & resistance. The slope of a CBF (coronary blood flow) vs. CPP graph gives 1/Resistance.

Renal autoregulation
There is "autoregulation" of renal blood flow and glomerular filtration rate in isolated kidneys. Howevever it is likely that both these parameters change to some extent in vivo, eg hypotension, during exercise. Autoregulation is the relative independence, from systemic blood pressure, of glomerular filtration rate and renal blood flow over the physiological range of mean arterial pressure (c.80-180 mmHg)