MICROANATOMY

Detailed explanation-1: -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-2: -Final answer: The maximum action potential generated by the sinoatrial node is 70-75/min.

Detailed explanation-3: -SA nodal action potentials are divided into three phases. Phase 4 is the spontaneous depolarization (pacemaker potential) that triggers the action potential once the membrane potential reaches threshold between-40 and-30 mV).

Detailed explanation-4: -Abstract. The cell of the sinoatrial (SA) node have a resting potential of-30 to-50 mV. This is a relatively low value compared to working myocardium. The response of the cells of the SA node to change in the extracellular potassium-concentration was small, viz, below 5 mM.