We just learned about Rapid Eye Movement.
Another part of sleep is the Circadian Clock.
The word circadian comes from the latin words Circa meaning about, and Dia meaning day. So circadian means about a day.
The circadian clock is like an clock inside the body that helps your body sleep at night and be awake during the day.
It is in the part of the body called the suprachiasmatic nucleus, or SCN.
This is a big bunch of nerves in the brain, that are hooked up to the eyeballs to sense daylight to know when it is night and day.
If your circadian clock gets out of order from too much TV at night, it can mess up your body's inside clock that helps you sleep.
(from: wikipedia - suprachiasmatic nucleus)
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