MEDICAL PHYSIOLOGY

Detailed explanation-1: -The sinus node continuously generates electrical impulses, thereby setting the normal rhythm and rate in a healthy heart. Hence, the SA node is referred to as the natural pacemaker of the heart.

Detailed explanation-2: -SA node pacemaker cells depolarize at a rate of 60 to 100 per minute, while the AV node at 40 to 60 per minute. The pacemaker with the highest rate of depolarization takes over as the primary pacemaker. In healthy individuals, this is the SA node.

Detailed explanation-3: -Closure of ion channels causes ion conductance to decrease. As ions flow through open channels, they generate electrical currents that change the membrane potential. In the SA node, three ions have a major role in generating the pacemaker action potential.