- A Contraction of the ventricular myocardium during systole as generally observed
- B Opening of the atrioventricular valves during diastole in typical laboratory settings
- C Closure of the atrioventricular valves at the start of systole under normal conditions
- D Closure of the semilunar (aortic and pulmonary) valves at the start of diastole
Correct answer: D. Closure of the semilunar (aortic and pulmonary) valves at the start of diastole
Explanation: The second heart sound ('dub') is produced by the closure of the semilunar valves (aortic and pulmonary) at the beginning of ventricular diastole.
Concept context
Blood, lymph, the heart, the cardiac cycle, blood pressure, and ECG. High NEET weightage.