Answer: Closed.
- A Open
- B Closed
- C Partially open
- D Absent
Correct answer: B. Closed
Explanation: When the ventricles contract, rising pressure closes the AV valves (producing the first heart sound) and forces open the semilunar valves so blood is ejected.
A single ECG cycle: the P wave marks atrial depolarisation (contraction signal), the large QRS complex marks ventricular depolarisation, and the T wave marks ventricular repolarisation (recovery) before the next cycle begins.
Concept context
Blood, lymph, the heart, the cardiac cycle, blood pressure, and ECG. High NEET weightage.