[MUSIC] Let's have a little primer for those of you who may have forgotten some of these terms, what various electrical terms mean. And so, let's consider the water analogy. In fact, electricity is very much like water for a lot of the terms. So let's consider that we have a landscape that's very flat. And there's a river or creek that's sitting here. If this is flat, is the water going anywhere? Eh, not so much, because all of this water is at the same level, and at the same level, it has the same potential. And so if the potential is, if there's no difference in their potential, then there's also no current. But now let's imagine that we come up here and we have a waterfall. Now there's going to be flow because we have a potential drop. This has a higher potential than this has, and water is going to go down and you're going to have a current. This potential drop will drive the current. Okay. And then consider what would happen if we had a higher waterfall. Well, this would have a greater potential than this would. And we would have more of a drop, more of a potential difference, and a higher current. One last thing to consider, if we now look down on this and we push this water through an opening that's this big, versus an opening that is this big, what have we changed? Well, we've changed the resistance. Here, there's more resistance, and so the amount of water that goes through there is going to be reduced. The current is going to be reduced here, and it will be greater in this larger channel. Electricity is just like that. And the things that we have to worry about when it comes to neuronal communication is potential. So potential in this context means what's the potential difference from inside the cell to outside the cell. And it's negative, let's say negative 65 millivolts. It varies. But around negative 65 millivolts. And remember that a millivolt is one one-thousandth of a volt. And the, another thing that we have to worry about is that we remember that there are ion channels that go and provide a way for ions to go in and out of a cell. And as they go in and out of the cell, they are carrying current. And finally, this whole cell has a resistance. If none of the channels are open, the resistance is very high, infinite, but if there are, let's say, three channels open, the resistance is high, but it's, and it's much lower if we now open, say, 100 channels. Okay? So those are the, in, within the context of a neuron, that's what we mean when we talk about potential. There's a potential difference across the membrane, across this, from the inside of the cell to the outside of the cell, there is current that goes through ion channels and there is a resistance between the inside of the cell and the outside of the cell. [MUSIC]