Look at the dominoes in the picture. If you push over the last domino, what happens? Each domino falls into the next, one at a time. This is similar to the way neurons carry messages from your brain to the other parts of your body.

What if several people knocked over dominoes in different parts of the path? What a mess! Some messages would get sent at the wrong time. Some messages would not be able to get through because their paths were blocked by the other dominoes.