A 65-year-old man complains of dizziness when he stands up quickly from bed. His BP is 130/80 mmHg supine 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: Normally, standing triggers baroreceptors to
increase HR and vasoconstriction. In elderly patients, this reflex may be
blunted → orthostatic hypotension.
A trauma patient loses ~20% of blood volume. Initially, BP is maintained.
Which mechanism helps maintain BP early?
A. Decreased sympathetic activity
B. Increased parasympathetic tone
C. Baroreceptor-mediated tachycardia
D. Decreased peripheral resistance
C.
Baroreceptor-mediated tachycardia
Explanation: Blood loss ↓ BP → baroreceptors trigger ↑ HR and
vasoconstriction to maintain BP.