Reversal potential

Imagine you and your friend are playing a game of catch with a ball. You are standing still and your friend throws the ball to you. You catch it easily. Now, imagine your friend throws the ball to you again, but this time he throws it really hard. You try to catch it, but it bounces off your hands and falls to the ground.

The reason you couldn't catch the ball the second time is because the ball was moving too fast for you to catch it. Similarly, in our body, cells use special channels to move tiny electrically charged particles called ions in and out. These channels work like doors that open and close, allowing ions to move in and out of the cell.

The reversal potential is like a "speed limit" for ions flowing through these channels. When ions move through these channels, they create a little electrical charge. This charge can push or pull other ions in and out of the cell as well. And when the overall charge of the cell changes, it can affect how the cell behaves.

So just like the ball moving too fast for you to catch, if ions are moving too fast or in the wrong direction through these channels, it can change the overall charge of the cell and affect how it functions. The reversal potential is the point at which the electrical charge of the inside of the cell equals the electrical charge of the outside of the cell. When ions reach the reversal potential, they stop moving because there is no longer an electrical difference to push or pull them.

Think of it like trying to fill a bucket with water. Once the bucket is full, you can't add any more water because the water level is the same inside the bucket and outside of the bucket. The same goes for ions moving through channels in a cell. Once they reach the reversal potential, they can't move any further because the electrical charge is the same inside and outside of the cell.