Brain and Nerves

Core Idea

Your brain is the control center of your body. It lets you think, feel, remember, and make decisions. Nerves are like wires that connect your brain to every part of your body. They carry messages back and forth so your brain knows what is happening and can tell your body what to do.

How It's Best Learned

Play a reflex game — have a partner drop a ruler and catch it as fast as you can. Discuss how your eyes saw the ruler falling, nerves sent a message to your brain, your brain decided to grab it, and nerves told your hand to close. Draw a simple diagram of brain-to-hand messaging.

Common Misconceptions

• Children may think the brain only does thinking and does not control physical movement.
• Some children think messages travel instantly (they are fast but not instant — that is why reaction time exists).
• Children may not realize the brain works even when they are asleep (it controls breathing, heartbeat, and dreaming).

Explainer

Inside your head, protected by your hard skull, sits the most important organ in your body: your brain. Your brain is where all your thinking happens — remembering your best friend's name, solving a math problem, imagining a story, deciding what to eat for lunch. But thinking is only part of what your brain does. It also controls everything your body does, from wiggling your toes to beating your heart.

Your brain needs a way to talk to the rest of your body, and that is what nerves do. Nerves are like tiny wires that run from your brain through your spine and out to every part of your body — your fingers, toes, eyes, ears, skin, and organs. There are billions of nerves in your body, forming a giant communication network.

Messages travel along nerves in two directions. When you touch something soft, nerves in your fingertips send a message up to your brain: "This feels soft!" When you want to kick a ball, your brain sends a message down through nerves to your leg muscles: "Kick now!" These messages travel incredibly fast — about 250 miles per hour in some nerves. That is why you can pull your hand away from something hot almost before you even feel the pain.

Your brain is always working, even when you do not think about it. Right now, your brain is keeping your heart beating, your lungs breathing, your food digesting, and your body balanced in your chair — all without you telling it to. When you sleep, your brain keeps all these systems running and also sorts through your memories and creates dreams. Your brain is the busiest organ you have, and nerves are the highways that connect it to everything else.