Answer: Tricuspid and bicuspid (atrioventricular) valves.
- A Valves present within the vena cava
- B Semilunar valves at the start of diastole
- C Tricuspid and bicuspid (atrioventricular) valves
- D Walls of the pulmonary artery during systole
Correct answer: C. Tricuspid and bicuspid (atrioventricular) valves
Explanation: The first heart sound (lub) results from the closure of the atrioventricular valves (tricuspid and bicuspid) at the start of ventricular systole.
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.