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Bio Biology

BiologyNEB 2075 (old course)

What is the function of the 'pacemaker' in the human heart?

1

Answer

· Based on the official syllabus and past papers
Updated

The pacemaker (sinoatrial node, or SA node) in the human heart is a specialized group of cardiac muscle cells located in the right atrium, near the entrance of the superior vena cava. Its primary functions are:

  1. Initiation of Heartbeat: The SA node generates electrical impulses (action potentials) spontaneously and rhythmically (60–100 times per minute in adults), setting the heart rate.
  2. Coordination of Atrial Contraction: These impulses travel through the atria, causing them to contract and pump blood into the ventricles.
  3. Regulation of Cardiac Cycle: The SA node acts as the natural pacemaker, ensuring synchronized contraction of the heart chambers via the atrioventricular (AV) node and Purkinje fibers.
  4. Adaptation to Physiological Needs: It adjusts impulse frequency in response to autonomic nervous system signals (e.g., accelerating during exercise via sympathetic stimulation or slowing during rest via parasympathetic input).

Disruption in SA node function (e.g., bradycardia or arrhythmias) can lead to irregular heart rhythms, necessitating artificial pacemakers.

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