Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The Sino-atrial node (SAN) is called the pacemaker of the human heart. Reason (R): The SAN can generate the maximum number of action potentials ( 70-75 per minute) among all nodal tissues. In the light of the above statements, choose the most appropriate answer from the options given below:

Step-by-step solution

The Sino-atrial node (SAN) is a specialised patch of cardiac musculature that has the ability to generate action potentials without any external stimuli (autoexcitable). Among all the nodal tissues, the SAN generates the maximum number of action potentials, which is 70-75 per minute. Because it generates the highest number of action potentials, it initiates and maintains the rhythmic contractile activity of the heart. For this reason, the SAN is called the pacemaker. Therefore, both the Assertion and the Reason are