nervous system

You hear a buzz, and swat at a mosquito. In that fraction of a second, a series of messages just traveled along your nervous system! First, signals raced from your ear to your brain, where you processed the sound and determined a mosquito was nearby. Then your brain sent messages along the nervous system to the muscles in your arm and hand--and the pesky insect is history!

Definition: a branching network of nerves linking your brain to every part of your body
Parts: brain, spinal cord, nerves
Cool Fact: Nerves carry signals in one direction. Some carry signals from the body to the brain. Others send messages from the brain to the body.
Cool Fact: The nervous system runs on electricity. But the levels are low. Brain signals involve less than one-tenth the voltage of an ordinary flashlight battery.

Image credits: main image, © AMNH/E.Hamilton.