Question

During phase 4 of the pacemaker action potential, which ion channel closes?

1) Sodium channel
2) Potassium channel
3) Calcium channel
4) Chloride channel

Answer 1

During phase 4 of the pacemaker action potential, the calcium channel closes.

Step-by-step explanation:

During phase 4 of the pacemaker action potential, the calcium channel closes. In phase 4, the membrane potential is at its lowest point (around -60 mV) and the calcium channels that were open during the previous phases close, preventing further influx of calcium ions. This closure of the calcium channels allows the membrane potential to remain stable until the next action potential is triggered.