Now, if we have some type of protein channel that opens up inside our cell membrane, then our sodium or any other ion can move across the cell membrane and they will always move down their electrochemical gradient. So, for example, if our sodium channels open up that carry sodium channels across the membrane, then the sodium channels will move down their electrochemical gradient from a higher concentration to a lower concentration from the outside to the inside. The same thing is true for calcium. The same thing is true for these other two. But for potassium, they will move in the opposite, because potassium has a higher concentration on the inside than on the outside. Now, when the cell is resting, our sodium as well as the calcium voltage gated channels are closed, but the potassium is able to actually leak into this or actually outside of the cell.