The brain produces enough electrical energy to power a 40-watt light bulb for 24 hours. That’s a lot of energy for a human organ a little bigger than a softball.
The brain is constantly active, even when we are asleep. As a matter of fact, asleep or awake, the brain requires 20 percent of the heart’s output of fresh blood and 20 percent of the blood’s oxygen and glucose to keep functioning properly. Glucose is a type of sugar that is our brain’s primary fuel.