The nervous system is your body's communication network, a vast collection of nerves and specialized cells that send messages between your brain and every part of your body. When you touch something hot, your nervous system instantly alerts your brain, which sends back a command to pull your hand away, all in a fraction of a second.

Your nervous system has two main parts. The central nervous system includes your brain and spinal cord, which act like a command center, processing information and making decisions. The peripheral nervous system is made up of all the nerves that branch out from your spine to reach your muscles, skin, and organs, like cables connecting a computer to its keyboard, mouse, and monitor.

Without your nervous system, you couldn't think, move, feel, or even breathe. It controls everything from conscious actions like kicking a soccer ball to automatic functions like your heartbeat and digestion. When you learn something new, your nervous system creates connections between brain cells. When you practice a skill repeatedly, those connections strengthen, which is why practice makes you better at sports, music, or math.

Scientists estimate that the human nervous system contains about 86 billion nerve cells, called neurons, which communicate through tiny electrical and chemical signals traveling at speeds up to 268 miles per hour.