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What happens when I sleep?

The brain of an awake and relaxed person generates alpha waves, which give consistent oscillations at about 10 cycles per second. An awake and alert person generates beta waves, which are about two times as fast.

During sleep, two slower patterns - theta waves and delta waves - take over. The oscillations for theta waves are about 3.5 to 7 cycles per second. Delta waves oscillate less than 3.5 cycles per second. As a person starts to fall asleep and when sleep deepens, the brainwave patterns slow down. Slower brainwave patterns mean deeper sleep - a person deep in delta wave sleep is very hard to wake up.

At several points through the night, rapid eye movement (REM) sleep occurs. Most people have three to five intervals of REM sleep per night. Brainwaves during this period speed up to awake levels. Watch a person or a dog experience REM sleep. You will see the eyes flicker back and forth rapidly. In most dogs and some people, arms, legs and face muscles twitch during REM sleep. Periods of sleeping other than REM are called NREM (non-REM) sleep.

You dream during REM sleep. If you wake a person during REM sleep, that person can vividly recall dreams. During NREM sleep, however, generally the person will not be dreaming.

Everyone needs both REM and NREM sleep for a good night's sleep. A normal person will spend approximately 25 percent of the night in REM sleep. The rest is spent in NREM. A REM session - in other word's, a dream - lasts five to 30 minutes.

Your body doesn't simply shut down as soon as you fall asleep. In fact, it's hard at work helping every mental and physical aspect of you function properly. No wonder the day after a bad night's sleep seems so terrible -- you didn't get to properly recharge.

From memory, to mood, to heart health, to your immune system and metabolism, there's pretty much nothing that sleep doesn't benefit.

Continue Learning about Sleep Basics

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Is Skimping on Sleep Okay?
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.