Sleep, Actually
REM and non-REM sleep
Sleep comes in two broad kinds: non-REM (three stages, from light to deep) and REM, where most vivid dreaming happens.
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NHLBI describes sleep in two broad types: non-REM sleep, which has three stages, and REM sleep — rapid eye movement sleep — where the eyes move quickly behind closed lids and most vivid dreaming occurs.
During REM, breathing and heart rate become more variable and most voluntary muscles are temporarily inactive, which is why people usually do not act out dreams.
In a typical night, sleep moves through non-REM stages first and then into REM, repeating through the night.
Definitions on this page
- REM sleep
- Rapid eye movement sleep, when most vivid dreaming happens.
- Non-REM sleep
- The three stages of sleep outside REM, from light to deep.
What does that mean?
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