Just like eating, sleep is necessary for survival. Sleep gives your body a rest and allows it to prepare for the next day. It's like giving your body a mini-vacation. Sleep also gives your brain a chance to sort things out.
Studies have shown that kids who regularly get an adequate amount of sleep have improved attention, behavior, learning, memory, and overall mental and physical health. Not getting enough sleep can lead to high blood pressure, obesity and even depression. Sleep is an essential function1 that allows your body and mind to recharge, leaving you refreshed and alert when you wake up. Healthy sleep also helps the body remain healthy and stave off diseases. Without enough sleep, the brain cannot function properly. Many biological processes happen during sleep: The brain stores new information and gets rid of toxic waste. Nerve cells communicate and reorganize, which supports healthy brain function. The body repairs cells, restores energy, and releases molecules like hormones and proteins.
When we shut our eyes to fall asleep, we begin to relax and fall into a very light sleep, which has been called "stage one" sleep. Our eyes begin to move left and right, back and forth, very slowly, many times, and very smoothly. It's called "slow-rolling eye movements" - and it's something we cannot do when we are awake. During stage one sleep, our brains start to produce slightly bigger waves, and fewer of them.
Next is "stage two sleep", which is a slightly deeper sleep than stage one sleep. There's not much that is special about what our eyes are doing, but there's a special wave that our brain makes called a "sleep spindle". It's a bit like the brainwaves seen in stage one sleep, but short, sharp and shiny.
The next stages of sleep are deep ones, and they are called stage three and four sleep. These stages are really deep, and hard to wake up from. The brainwaves become big - like those you might have seen at the beach.
Finally, one of the most interesting stages of sleep is called "REM sleep". REM stands for Rapid Eye Movement - so it means our eyes are moving all over the place during sleep - like when we're awake. And our brain waves are very similar to when we're awake. But it's during REM sleep that we dream.
Our brains move through the different stages of sleep - from one, two, three, four, and then back to REM sleep. We go up and down through these stages all night until we wake in the morning.
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