The Nervous System

body · brain · super fast

Two main parts. The central nervous system is your brain and spinal cord, while the peripheral nervous system is the network of nerves reaching the rest of your body.

Speedy messengers. Nerves carry signals as bundles of long fibers called axons, connecting your brain to everything from your toes to your fingertips.

Two-way traffic. Sensory nerves send information from your body to your brain, and motor nerves carry the brain's commands back out to your muscles.

Calm or alarm. The sympathetic system fires up in emergencies to give you energy, while the parasympathetic system helps you relax and rest.

Ancient origins. Nervous tissue first appeared in wormlike creatures about 550 to 600 million years ago.