What are the effects of the plateau phase of the contractile cell action potential?

Video transcript

Hi everyone. Let's take a look at this practice problem together which of the following statements about the plateau phase of a cell's action potential is true. The answer options are a, it shortens the duration of an action potential. B it ensures repolarization for a sufficient period. C voltage gated calcium channels closed during this time and D it helps prevent Teton contractions. So recall that the plateau phase of a cell's action potential is when that membrane potential remains almost constant. And that is due to slow calcium channels. These channels allow calcium influx while there's only a little bit of potassium efflux. So what is true about this plateau phase? Well, option A, it shortens the duration of the action potential. This is incorrect, slow calcium channels in the plateau phase actually prolongs the action potential. So option A, we can eliminate option B, it ensures rep polarization for a sufficient period during the plateau phase. Again, those slow calcium channels allow for depolarization to be maintained, not repolarization. So we can also eliminate option B. Option C, the voltage gated calcium channels are closed. This is also incorrect during that plateau phase. The slow calcium channels are open and that is what helps to maintain that plateau. So the correct answer has to be that it helps prevent tetanic contractions. Recall that these contractions are a continuous and sustained contraction. Now, what the plateau phase does is it makes that refractory period longer. And that means that there's a longer period of time where the cell will not respond to additional stimuli. So the correct answer is option d it helps prevent tetanic contractions. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.