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Learn about the 4 main sleep stages and circadian rhythms. By Carole Yue. More free lessons at:

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These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.

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    There are five stages in the sleep cycle. These stages include non REM and REM sleep. REM stands...

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current07:57, April 22, 2015Thumbnail for version as of 07:57, April 22, 201507:57480 × 269 (20 KB)Ash204 (wall | contribs)created video


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