Cerebral autoregulation maintains constant cerebral blood flow (CBF) over a mean arterial pressure (MAP) range of approximately:
- A 60–150 mmHg ✓
- B 40–60 mmHg
- C 100–180 mmHg
- D 50–200 mmHg
Explanation
Normal cerebral autoregulation maintains CBF (~750 mL/min or 50 mL/100g/min) constant between MAP of approximately 60–150 mmHg through myogenic and metabolic mechanisms in cerebral arterioles. Below 60 mmHg, vasodilation is maximal and CBF falls passively; above 150 mmHg, vasoconstriction is overcome and cerebral 'breakthrough' hyperperfusion occurs (hypertensive encephalopathy). In chronic hypertension the autoregulatory curve shifts rightward (to ~100–180 mmHg), explaining why rapid antihypertensive treatment can cause ischaemia in hypertensive patients if MAP falls below their shifted lower limit.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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