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Sleep—Luxury or Necessity?Awake!—2003 | March 22
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Approximately two hours after we fall asleep, our eyes begin to quiver quickly back and forth. The observation of this phenomenon led scientists to divide sleep into two basic phases: REM (rapid eye movement) sleep and non-REM sleep. Non-REM sleep can be subdivided into four stages of progressively deeper sleep. During a healthy night’s sleep, REM sleep occurs several times, alternating with non-REM sleep.
Most dreaming occurs during REM sleep. The body also experiences maximum muscle relaxation, which allows the sleeper to wake up feeling physically refreshed. In addition, some researchers believe that newly acquired information is consolidated as part of our long-term memory during this sleep stage.
During deep sleep (non-REM sleep stages 3 and 4), our blood pressure and heart rate reach lower ranges, providing rest for the circulatory system and helping to ward off cardiovascular disease. In addition, the production of growth hormone peaks during non-REM sleep, with some teenagers producing as much as 50 times more growth hormone at night than during the day.
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Sleep—Luxury or Necessity?Awake!—2003 | March 22
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[Graph on page 5]
(For fully formatted text, see publication)
THE STAGES OF SLEEP
Simplified graph
Stages of sleep
Awake
REM
Non-REM
Light sleep 1
2
3
Deep sleep 4
1 2 3 4 5 6 7 8
Hours of Sleep
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