All right. So here we have a graph depicting the change in membrane potential during an action potential. So within this graph, we're going to be writing the state of the voltage-gated sodium and potassium channels, if they're open or closed, during each of the main phases of our action potential. And as a reminder, the main phases are when we start at rest, then we depolarize, and then we repolarize, and then we hyperpolarize. So let's start at rest.

Now keep in mind, we are working with voltage-gated channels. And when our cell is at rest, all of our voltage-gated channels are closed. So I'm going to put that here for sodium and for potassium. Both of them are closed. Now when our cell starts depolarizing and gets to negative 55, our voltage-gated sodium channels are going to open.

So I'm going to write open over here because during that depolarization phase, our voltage-gated sodium channels are open. And that's going to cause sodium, positive sodium, to come rushing into our cell, and that's going to bring up our membrane potential. Now, during this phase, the potassium channels are closed. Nothing's going on there. Now once our cell has depolarized up to about positive 30, remember we have that flip where now our sodium channels are going to be closed.

And at positive 30, our voltage-gated potassium channels open. So we're going to write open here. And that is going to cause repolarization because all that positive potassium is going to now leave our neuron, and the loss of all of those positive ions will make our cell become more negative again. Now, as we're doing that, we're going to overshoot that repolarization, and we're going to hyperpolarize. Now, at this stage, our sodium channels are in the same state.

Nothing has changed there, so they are closed. And remember, during hyperpolarization, our potassium channels are in the process of closing. So they start closing at around negative 50, and when we're hyperpolarizing, they're still closing. There might be a couple stragglers that are still open. So I'm going to write closing here just to help us remember that there might be a couple that are open, but they're in the process of closing.

And right as soon as all of them have finally closed, so all of our voltage-gated sodium and potassium channels are all closed, we'll get back to rest where everything is closed again. All right. So there you have it, and I will see you guys in the next one. Bye bye.