During sleep, our bodies proceed through a series of stages, with each stage serving a function in restoration and rejuvenation of different areas of the body.  As people move from waking state through deeper stages of sleep, brainwaves become slower and more rhythmic and we move from awake to non-REM sleep to REM sleep.  After a period of REM sleep, we descend again through the initial stages with a complete cycle of REM and non-REM occurring approximately every 90 minutes.   As the night progresses we spend less time in deeper sleep and more time in REM sleep.

Sleep Science - Brain xRay

What happens in the brain?

“Out like a light” couldn’t be further from the truth in regards to brain activity during sleep.  Groups of cells within the hypothalamus and the parafacial zone in the brain stem, when switched on, trigger a loss of consciousness.  During REM, when dreaming occurs, our muscles become paralyzed and deeply rested, preventing involuntary movements and breathing and heart rate become erratic.  Interestingly, despite our understanding of the biochemistry and neurobiology that occurs, the exact purpose of REM sleep remains undefined.

Sleep Science - activity scan

When your body goes on night shift

During non-REM sleep, our heart rate and blood pressure reduces, allowing for our hearts to have a rest from the amount of activity they have to do during the day.  The intestines quiet down and the liver goes from trying to detoxify during wakefulness to build and synthesize when we’re sleeping.   Our breathing slows and becomes more regular, giving our lungs a rest and our muscles have a chance to repair thanks certain growth hormones released during sleep.

How much sleep should I get?

The National Sleep Foundation recommends the following sleep requirements over a lifespan.

Development StageAgeHours
Older Adult> 65 years7 – 8 hours
Adult26 – 64 years7 – 9 hours
Young Adult18 – 25 years7 – 9 hours
Teenager14 – 17 years8 – 10 hours
School Age6 – 13 years9 – 11 hours
Preschool3 – 5 years10 – 13 hours
Toddler1 – 2 years11 – 14 hours
Infant4 – 11 months12 – 15 hours
Newborn0 – 3 years14 – 17 hours

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