All or none

So imagine you have a light switch like the one in your room. When you turn it on, the light comes on - this is the "all" part. There's no in-between, it's either on or off.

The same thing happens in the body with certain cells called neurons. These neurons send signals to the brain and other parts of the body to tell them what to do. When a neuron sends a signal, it's like turning on the light switch - the signal goes all the way through or it doesn't go at all. This is the "none" part.

So it's like pressing a button - you either press it all the way down and the signal goes through, or you don't press it at all and the signal doesn't go through. There's no halfway point. It's a simple way for the body to make sure signals get where they need to go without getting jumbled up.