The brain may simply be the bossiest part of the body: It tells virtually every other part of your body what to do, all the time, whether you’re aware of it or not. It controls what you think and feel, how you learn and remember, and the way you move. It also controls things you might not think about — like the beating of your heart and whether you feel sleepy or awake.
If the brain is like a central computer that controls all the functions of your body, then the nervous system is like a network that sends messages back and forth from the brain to different parts of the body. It does this via the spinal cord, which runs from the brain down through the back and contains threadlike nerves that branch out to every organ and body part.