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A specialised patch of muscle in the wall of the right atrium starts each heartbeat on its own, earning it the title 'pacemaker'. This structure is which node?
AAtrioventricular node
BBundle of His
CSino-atrial node
DPurkinje fibres
Answer & Solution
Correct answer: C. Sino-atrial node
1. The pacemaker initiates the impulse and sits in the right atrium wall.
2. The AV node relays the impulse later, so it is not the initiator, ruling out option A.
3. Bundle of His and Purkinje fibres conduct the impulse to ventricles, not start it, ruling out options B and D.
4. The self-starting pacemaker is the sino-atrial node, option C.
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 14 Transportation in Plants and Circulation in Animals "Initiation and conduction of Heart beat", p.216_
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