About Normal Sleep Cycles
Getting a good night's sleep is essential for your health. If you go for too long without adequate sleep you can develop serious health problems. There are different stages of sleep, which tend to go in cycles. There are four non-rapid eye movement cycles (NREM) and one rapid eye movement (REM) cycle.
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Stage One
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This is the stage where you start to feel drowsy. The eyes are closed but you can be awakened easily, and if awakened you may not even realize that you were asleep. This stage lasts for about five to ten minutes.
Stage Two
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This stage occurs during light sleep. There are periods of muscle activity and periods of muscle rest. Your heart rate and breathing rate slow, your body temperature drops and the body prepares for deep sleep. Approximately fifty percent of your time sleeping, is in this cycle.
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Stage Three and Stage Four
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Stage three is the first stage of deep sleep. Delta waves begin to appear in this stage along with faster waves. Stage four is the second stage of deep sleep. This is the stage where Delta waves are predominant and the body is working to restore itself.
REM Cycle
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This stage is where dreaming occurs. During REM sleep your muscles become immobilized, so you do not physically act out your dreams. However, your heart and breathing rate increases and brain wave activity is similar to someone who is wide wake. During a normal night's sleep you tend to go through about two hours of REM sleep per night.
Sleep Cycles
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The four stages of NREM sleep can last from five to fifteen minutes. Stages two and three repeat backwards before REM sleep occurs. REM sleep normally occurs about ninety minutes after sleep onset. The first stage of REM sleep lasts about ten minutes. It gets progressively longer with each cycle, with the last phase lasting about one hour. The whole process cycles about four to five times during and eight hour sleep period.
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