What Is Sleep?

Expert reviewed on
February 02, 2024
woman sleeping

There was a time when people thought that sleep was simply a time when the body and brain “shut off” and idled for the night in preparation for the next day. But now scientists understand that neither the body nor the brain “shut down” when we sleep; in fact, they are actively, refining brain circuits, clearing metabolic waste products, repairing injury, growing bones and building muscles. 

Circadian rhythm

Imagine you have a tiny clock inside your brain, consistently sending reminders to the rest of your body. This clock, called your circadian rhythm, runs on a roughly 24-hour cycle, like a day-night cycle inside you, even without any sun!

Think of the days light-dark cycle like a traffic signal for your body. Sunlight acts like the green light, telling your clock to speed up and make you energetic (like morning rush hour). When it's dark, the clock turns yellow and then red, slowing things down and making you sleepy (like bedtime).

This internal clock isn't just about sleep. It's a master timer for all of your body functions, controlling when you feel hungry, when your gut moves, making sure hormones are released at the right time and even helping you be at your creative peak when you sit down to write or think. When you have a healthy circadian rhythm it keeps everything running smoothly throughout the day and night.

So, the next time you feel a surge of energy in the morning or sleepiness at night, remember your tiny clock inside. It's just trying to keep your body in sync with the world around you. By understanding your circadian rhythm and respecting its cues, you can feel better and be more productive throughout the day. Abnormalities in the circadian rhythm can lead to sleep disorders like insomnia at night and excessive sleepiness during the day.