system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the electricity in our body get there?

I’m referring to the electricity that is involved with the heart beating and brain signals. How does it get into us to begin with when we are a fetus, and how does it keep being produced?
gpt
Think of electricity as the flow of charge between a high-energy area and a low-energy area. This is very similar to holding a ball up in the air and letting go: while you're holding the ball, the potential energy is high (it has the potential to fall some distance) relative to when it's on the ground (the potential for it to fall is zero) - the act of falling is the "electricity".

So our bodies create electricity by using "electrolytes", the major players of which are Sodium (Na) and Potassium (K). If we take a single nerve cell and look at how it sends an electric signal down its length, we'll see that the inside of the nerve has a lot of K and the outside of the nerve has a lot of Na. The amount of these is different, and there's a LOT more Na than there is K. Both of these are positively charged, but because there's a LOT more positive charge outside the cell... those ions really want to get in.

So that's our potential. Lots of Na outside, less K inside, the ions want to move in to make everything nice and even. Channels open for the Na to rush inside and K to rush out, and now, because they're moving, electricity is formed. Our bodies are able to use this electricity for a bunch of things, mainly cells sending signals to other cells. When the signal is done, those channels close up and pumps (Na-K ATPase) push Na back out of the cell and K into it to reset. This requires chemical energy, rather than electrical, which comes from breaking down sugar.