Coronary blood flow is maintained constant over a range of perfusion pressures (approximately 60 to 180 mmHg) despite changes in mean arterial pressure. This phenomenon is best termed?
- A Autoregulation ✓
- B Reactive hyperemia
- C Active hyperemia
- D Pressure natriuresis
Correct answer: A. Autoregulation
Explanation
Autoregulation maintains relatively constant coronary blood flow over a range of perfusion pressures (approximately 60 to 140 mmHg in coronaries). It is mediated by myogenic responses and metabolic factors (adenosine, nitric oxide) that adjust arteriolar tone. Reactive hyperemia is the transient increase in flow after ischemia. Active hyperemia is flow increase due to metabolic demand. Pressure natriuresis is a renal mechanism unrelated to coronary flow.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
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