Which node is known as the pacemaker of the heart?

Which node is known as the pacemaker of the heart?

• A. Sinoatrial (SA) node.
• B. Atrioventricular (AV) node.
• C. Purkinje fibers.
• D. Bundle of His.

Answer: (A)

The main idea is that the heart’s natural pace is set by the sinoatrial node because it has the highest rate of automaticity among the conduction system. Located in the right atrium near the superior vena cava, its pacemaker cells spontaneously depolarize fastest, generating impulses about 60–100 times per minute under normal conditions. This rapid, regular firing sets the rhythm that initiates atrial contraction and drives the rest of the conduction pathway. From there, the impulse travels to the atrioventricular node, which provides a brief delay to ensure the ventricles fill properly, before moving through the His bundle and Purkinje system to cause ventricular contraction. The AV node and Purkinje fibers have slower intrinsic rates and act as backup or conduction pathways rather than the primary pace. If the SA node fails, the heart can still beat, but usually at a slower rate set by the AV node or Purkinje system.

The main idea is that the heart’s natural pace is set by the sinoatrial node because it has the highest rate of automaticity among the conduction system. Located in the right atrium near the superior vena cava, its pacemaker cells spontaneously depolarize fastest, generating impulses about 60–100 times per minute under normal conditions. This rapid, regular firing sets the rhythm that initiates atrial contraction and drives the rest of the conduction pathway.

From there, the impulse travels to the atrioventricular node, which provides a brief delay to ensure the ventricles fill properly, before moving through the His bundle and Purkinje system to cause ventricular contraction. The AV node and Purkinje fibers have slower intrinsic rates and act as backup or conduction pathways rather than the primary pace. If the SA node fails, the heart can still beat, but usually at a slower rate set by the AV node or Purkinje system.