Cardiac Conduction System (SA, AV Nodes) · NCERT Biology

Which structure acts as the primary pacemaker of the human heart?

  1. Atrioventricular (AV) node
  2. Purkinje fibres
  3. Sinoatrial (SA) node
  4. Bundle of His
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Correct answer: Sinoatrial (SA) node

The sinoatrial (SA) node initiates electrical impulses that set the basic rhythm of the heart. It has the highest intrinsic rate of spontaneous depolarisation among all cardiac tissues, so it functions as the primary pacemaker.

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