Answer: SA node.
- A SA node
- B AV node
- C Purkinje fibre
- D bundle of His
Correct answer: A. SA node
Explanation: The sino-atrial (SA) node initiates each heartbeat.
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.