Answer: Ventricular contraction.
- A Ventricular contraction
- B Atrial contraction
- C Ventricular relaxation
- D Closure of semilunar valves
Correct answer: A. Ventricular contraction
Explanation: The QRS complex marks the depolarisation of the ventricles, which initiates ventricular contraction (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.