1. A 65-year-old man complains of dizziness when he stands up quickly from bed. His BP is 130/80 mmHg in supine position and 100/60 mmHg after standing for 2 minutes. What is the most likely physiological cause?
A. Increased vagal tone
B. Impaired baroreceptor reflex
C. Increased ADH secretion
D. Increased renin secretion
B. Impaired baroreceptor reflex
Explanation:
- Standing triggers baroreceptors to increase HR and vasoconstriction. In elderly patients, this reflex may be blunted causing orthostatic hypotension.