Question

Match the channel type with the appropriate description.

These channels open during the plateau phase of the cardiac contractile cell action potential.

A) voltage-gated sodium channels
B) potassium channels
C) funny channels
D) T-type calcium channels
E) L-type calcium channels

Answer 1

During the plateau phase of the cardiac contractile cell action potential, L-type calcium channels open, allowing calcium to enter the cell and prolonging the contraction phase.

Step-by-step explanation:

The proper channel type that opens during the plateau phase of the cardiac contractile cell action potential is the L-type calcium channels. The sequence of events starts with the rapid depolarization phase where voltage-gated sodium channels open and allow an influx of Na+ ions. This action potential rise to about +30 mV before it enters the plateau phase. During this phase, the L-type calcium channels open, allowing a slow, continued influx of Ca2+ ions while very few potassium channels are open. This phase lasts for an extended period, during which the cell sustains contraction. After the plateau phase comes the repolarization phase, where the L-type calcium channels close and potassium channels open, allowing K+ ions to exit, returning the membrane potential to resting levels.