Yep, it’s true. There’s always a weak amount of electricity flowing in everyone’s body. Imagine you’re playing baseball. When your eyes see a ball rolling toward you, what do you think happens inside your body? Your nerves send a weak electric signal to your brain about what you see or what you want your body to do. For example, the nerves send a signal saying “A ball is coming”. Then your brain sends an electric signal saying “Pick up the ball” to your nerves. Your nerves relay the signal to the muscles in your hands and legs. This is how your body moves to pick up the ball.

In the similar way, doctors can figure out the condition of your body by the state of the electricity flowing in your body. For example, doctors use machines that measure electric signals in the brain called brain waves or electric signals created by heartbeats. The machines draw the signals as a picture called an electrocardiogram, or ECG. ECGs are useful because doctors can look at them and check for illnesses.