Question

Which of the following ion channels must open for a cardiac pacemaker cell to depolarize to threshold for an action potential?

A) funny channels only
B) L-type calcium channels only
C) T-type calcium channels only
D) both funny channels and L-type calcium channels
E) both funny channels and T-type calcium channels

Answer 1

Both funny channels and L-type calcium channels must open for a cardiac pacemaker cell to depolarize to threshold for an action potential.

Step-by-step explanation:

The ion channels that must open for a cardiac pacemaker cell to depolarize to threshold for an action potential are both funny channels and L-type calcium channels. Funny channels, also known as hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, allow a slow influx of sodium ions which causes the membrane potential to rise slowly. L-type calcium channels, on the other hand, allow the entry of calcium ions, further depolarizing the cell.