Okay. So now that we understand how and why those ions move, let's take a look at where those ions actually are. And for context, we'll be looking at these ion concentrations in a cell that is at rest. So our neuron is not communicating, just taking a little break. So, when our cell is at rest, what we typically see is that for sodium, we have a relatively low intracellular concentration, so not very much sodium inside of our cell, but we do have a very high concentration of sodium outside the cell; and we see the opposite pattern for potassium.

So for potassium in a cell that is resting, we tend to have a very high concentration inside the cell and a low concentration outside the cell. Alright, so easy peasy lesson there, right? Let's dive right into our example to kind of visualize this and practice those gradients a bit. So what we're going to be doing here is, given what we just learned about those sodium and potassium concentrations, we'll be drawing an arrow in these boxes to indicate which direction the concentration and electrical gradients will be directing the flow of these ions. So to quickly orient you to our image here, in case you haven't seen this before, the orange here is our membrane.

This tan area is our negatively charged cytosol. This blue area is our positively charged extracellular fluid. We have our pink potassium ion and our little purple sodium ion and our little pink potassium leak channel there, and our sodium leak channel. Remember, these guys are always open. Ions are coming in and out, and just looking at these pink and purple sodium and potassium ions, I can see that these concentrations are what we just talked about.

So I'm counting 1, 2, 3, 4, 5 potassium ions in the cell, our high concentration, and 2 outside the cell, that's our low concentration, and the opposite pattern for sodium. So I see 1, 2, 3, 4, 5 sodium ions out of the cell. That's our high concentration and just 2 inside the cell. That's our low concentration. So let's start with those concentration gradients since we've been talking about that this whole time.

So remember, ions are like introverts. Right? They want to get out of a crowd, go from their high to low concentrations. So for potassium, that's going to be directing the flow out of the cell. Right? The high concentration is in. They want to get away from that, so they're going to be going out of the cell. And for sodium, we'll see the opposite pattern. So our high concentration is outside the cell, so they're going to want to move into the cell. And so the electrical gradients for these are actually going to be the exact same because they're both positively charged ions, and remember, opposites attract, right, so they're both attracted to this negatively charged cytosol.

And so for both of these ions, the electrical gradients will be directing the flow into the cell. Alright. And you can see kind of a nice example here of what I mentioned in our last video how sometimes these gradients can be opposing, and sometimes they can be more synergistic. So for our potassium, we have these opposing gradients with the concentration gradient directing the flow out and the electrical gradient directing the flow in. And this is a cartoon.

Obviously, we don't have enough information to figure out which one is stronger and would drive net flow, but it gives you kind of a nice idea and a nice comparison to sodium here where both gradients are directing the flow into the cell. So you can tell we're going to have a pretty strong net flow of sodium. Alright. So that is the sodium and potassium concentrations of a cell that is at rest, and I will see you guys in our next video.