Now, just as quickly as these sodium voltage gated channels open, they close. Remember, because they're time dependent, they are only open for a very small fraction of a second. So as soon as we reach this highest point of positive 30 millivolts, these sodium voltage gated channels basically close very quickly. And at the same time, potassium voltage gated channels begin to open. But they begin to open very slowly. And so this is described in the following diagram.