MEDICAL PHYSIOLOGY

Detailed explanation-1: -Pacemaker current occurs due to the slow influx of Na+ ions through the hyperpolarization-activated cyclic nucleotide-gated channel (HCN channel). [9] This pacemaker current causes the membrane potential to change from-60mV to reach the threshold potential of-40mV.

Detailed explanation-2: -FUNNY Na ion channels are responsible for the spontaneous depolarization seen in pacemaker cells, which OPENS during REPOLARIZATION so it prevents the membrane potential from becoming more negative and provides a constant positive inflow.

Detailed explanation-3: -Therefore, action potentials in non-pacemaker cells are primarily determined by relative changes in fast Na+, slow Ca++ and K+ conductances and the corresponding ion currents.