Which of the following specialised cardiac musculatures has the intrinsic ability to generate the maximum number of action potentials without any external stimuli and is responsible for initiating the rhythmic contractile activity of the heart?

Step-by-step solution

The entire nodal musculature is autoexcitable, meaning it can generate action potentials without any external stimuli. However, the sino-atrial node (SAN) generates the maximum number of action potentials, i.e., 70-75 per minute. This makes it responsible for initiating and maintaining the rhythmic contractile activity of the heart, which is why the SAN is called the pacemaker. The atrio-ventricular node (AVN), bundle of His, and Purkinje fibres also possess autoexcitability but have progressively lower intrinsic r