Answer: atrioventricular valves.
- A atrioventricular valves
- B the semilunar heart valves
- C the main aorta wall
- D the vena cava vein
Correct answer: A. atrioventricular valves
Explanation: "Lubb" is caused by the atrioventricular (bicuspid and tricuspid) valves closing.
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.