Cardiovascular reflexes: Valsalva: practice question

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Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Blood pressure overshoots above baseline and heart rate falls, because sympathetic vasoconstriction persists while venous return is restored and the baroreflex responds

During straining, venous return and cardiac output fall, blood pressure drops and baroreceptor-driven sympathetic activity rises. When the strain is released, cardiac output recovers into a vasoconstricted circulation, so pressure overshoots; the baroreflex then slows the heart (reflex bradycardia) until values normalise.

Option by option

• A. Blood pressure and heart rate both rise, because of cardiac sympathetic overactivity

  Heart rate falls after the overshoot because baroreceptors are stimulated; it does not rise.

• B. Blood pressure overshoots above baseline and heart rate falls, because sympathetic vasoconstriction persists while venous return is restored and the baroreflex responds (correct)

  Correct. Restored output into constricted vessels causes the overshoot, followed by reflex bradycardia.

• C. Blood pressure falls and heart rate rises, because venous return is reduced

  This describes phase II, the straining phase, not release.

• D. Blood pressure and heart rate return to baseline at once with no overshoot

  A transient overshoot with bradycardia is the normal response; instant return is not seen.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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