NEET Zoology Question (2026) — Solution

Step-by-step solution

The sino-atrial node (SAN) is a specialised patch of cardiac musculature present in the right upper corner of the right atrium. It has the ability to generate action potentials without any external stimuli, making it autoexcitable. The SAN can generate the maximum number of action potentials, which is 70-75 per minute in a healthy human. This rate of action potential generation is responsible for initiating and maintaining the rhythmic contractile activity of the heart, which is why the SAN is called the pacemaker. Consequently, the normal human heart beats 70-75 times per minute (average 72 beats per minute).