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The number of action potentials generated by sino-arterial node (SAN) in a healthy human is ___ per minute.
SAN Action Potentials = Normal Heartbeat = 70–75 beats/min!
A specialized cardiac musculature called nodal tissue is distributed in the heart. A patch of this tissue called the Sino-atrial node (SAN) is located in the upper right corner of the right atrium.
Different parts of the conducting system can generate action potentials at different inherent frequencies: SAN generates 70–75 min⁻¹, AVN generates 40–60 min⁻¹, and Purkinje fibers generate 20–40 min⁻¹. Because SAN possesses the highest intrinsic rate, it commands heart contraction.
Option (1) gives 28-30 (characteristic of severe heart block / slow Purkinje rhythm). Option (3) gives 100-110 (tachycardia). Option (4) gives 120-140 (strenuous exercise). The basal rate is 70-75.
Diagnose every choice: Know exactly why the right option works and why distractors fail.
Incorrect. Represents ectopic ventricular/Purkinje fiber intrinsic firing rate.
100% accurate. Canonical NCERT rate of SAN autorhythmicity.
Incorrect. Represents sinus tachycardia, not normal resting generation.
Incorrect. Exceeds standard physiological baseline.
The NEET question paper misprinted "sino-atrial node" as "sino-arterial node". Students should never get distracted by obvious typographical errors in anatomy names.
"The sino-atrial node (SAN) generates 70–75 action potentials per minute, establishing it as the primary pacemaker of the mammalian heart."
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