A patient with longstanding essential hypertension has a baseline mean arterial pressure of 130 mmHg yet reports no postural symptoms when sitting up suddenly. The physiological basis for this tolerance is:

• A The baroreceptors have become permanently denervated by sustained wall stress
• B Arterial baroreceptors have reset their operating range upward over weeks to months, so they now defend the elevated pressure as normal ✓
• C Chemoreceptors have taken over short-term pressure regulation from the baroreceptors
• D Renal fluid retention has abolished the need for neural buffering of acute pressure changes

Explanation

Baroreceptors adapt or reset within one to two days of a sustained pressure change, restabilizing firing at the new level. In chronic hypertension the entire stimulus-response curve shifts rightward, so the elevated pressure sits at the center of the new operating range and is defended normally against acute perturbations. Denervation does not occur, chemoreceptors regulate ventilation rather than serving as the primary pressure buffer, and renal mechanisms act too slowly to explain acute postural stability.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.