Describe generation of pacemaker action potentials

Question

What will be an ideal response?

Answer 1

Pacemaker potentials in nodal pacemaker cells depend on three currents: an increased inward sodium current, a decreased outward potassium current, and an increased inward calcium current. These pacemaker potentials precede the action potential and drive the cell toward threshold. The initial inward sodium current is through voltage-gated channels, but these channels are unusual (and are called funny channels) because they open when the membrane potential becomes hyperpolarized. This occurs at the end of a previous action potential and immediately starts the membrane potential moving toward threshold again. At the same time, potassium permeability is decreasing as the potassium channels that opened during the falling phase of the previous action potential close. The combination of the two events contributes to a depolarizing potential and movement toward threshold. The next phase of the pacemaker potential is dependent upon the opening of T-type calcium channels. As these channels open, calcium enters the cell, further depolarizing it and driving it toward threshold.