Sleep begins with NREM sleep, progressing through the three basic NREM sleep stages, sleep stages 1 and 2 and slow wave sleep. NREM sleep is then followed by a relatively short REM sleep episode. The time between falling asleep and the end of the REM episode constitutes a sleep cycle.
NREM Sleep
Stage 1
Sleep is very light sleep and it occurs during transitions from awake to asleep. Your muscle tone begins to decrease during this stage but slow eye movement continues. Most people don’t even notice that they’re sleeping at this point.
Sleep is very light sleep and it occurs during transitions from awake to asleep. Your muscle tone begins to decrease during this stage but slow eye movement continues. Most people don’t even notice that they’re sleeping at this point.
Stage 2
During this stage of sleep, eye movements stop, and brain waves slow—with intermittent rapid wave bursts called “sleep spindles”. Most people when woken-up from stage 2 sleep realize that they were sleeping. If you’ve ever woken someone up during this stage, you probably noticed that the person slowly opened their eyes, looked around confusedly, and then went back to sleep.
During this stage of sleep, eye movements stop, and brain waves slow—with intermittent rapid wave bursts called “sleep spindles”. Most people when woken-up from stage 2 sleep realize that they were sleeping. If you’ve ever woken someone up during this stage, you probably noticed that the person slowly opened their eyes, looked around confusedly, and then went back to sleep.
Stages 3 and 4 (slow-wave sleep)
In these stages brain waves slow further to a pattern called “delta waves” mixed with occasional spurts of faster waves. Heart rate and body temperature continue to drop, along with blood pressure and muscle tone. Eye movements remain absent. This is the deepest most restorative stage of sleep. If your alarm clock goes off during slow-wave sleep, you may feel confused and groggy for several minutes after waking up.
In these stages brain waves slow further to a pattern called “delta waves” mixed with occasional spurts of faster waves. Heart rate and body temperature continue to drop, along with blood pressure and muscle tone. Eye movements remain absent. This is the deepest most restorative stage of sleep. If your alarm clock goes off during slow-wave sleep, you may feel confused and groggy for several minutes after waking up.
REM Sleep
This is when you do most of your dreaming, and is a time when your brain is actively encoding lessons that you learned and memories that you made throughout the day. Some people have called this type of sleep “paradoxical sleep” because it involves relatively fast brain activity and irregular heart rate and blood pressure, as well as characteristic rapid eye movements. During REM sleep your limbs are temporarily paralyzed, perhaps to keep your body from acting out action packed dreams.
Your sleep progresses through these cycles of NREM and REM sleep about every 90 minutes. Your brain engages in most slow wave sleep earlier in the night, which will ensure you get enough of this most restorative sleep state even if you cut your night short by an early morning meeting. If this happens to be the case, just remember that you can always catch up on sleep with a short nap during the day!
- StanfordOnline SOM, Staying Fit
No comments:
Post a Comment