You may be surprised to learn that we still don’t fully understand why people need to sleep and what purpose sleep serves. Doctors and researchers had thought many years ago that sleep was a single state of being that was distinguished from waking. However, we now know that sleep itself is divided into two distinctly different states: REM, or rapid eye movement sleep, and non-REM sleep.
Non-REM sleep is the state of sleep entered when we first start to doze off. Non-REM sleep state has four stages with each stage lasting from 5-15 minutes. This stage of sleep is probably the closest to what we usually think of as “sleep.” The first stage of non-REM sleep is the state of drowsiness. In this stage one can be awakened easily, and is usually referred to as “daydreaming.” As you continue into a deeper sleep, you may notice or be awakened by a sudden jerk of your whole body called hypnic mycological, a normal response for most people. Stage three and finally stage 4, are deeper and deeper levels of sleep. During these stages it will be much more difficult to wake up and if you are woken up, you may feel disoriented for a minute or so. In non-REM sleep, your muscles are more relaxed than when you are awake. You still have the ability to move, however, you lie still because your brain is not sending messages to your muscles to move. The body usually goes through one or two cycles of non-REM sleep before entering the next phase of sleep, called REM sleep.
REM sleep usually occurs 90 minutes after you fall asleep and varies greatly from non-REM sleep. The first period of REM sleep typically last 10 minutes, while the final one may last up to an hour. Intense dreaming occurs during REM sleep as a result of heightened brain activity. REM sleep is an active state requiring significantly more oxygen than the non-REM phase, a sign that you are expending more energy during REM sleep. The most striking feature of REM sleep is the bursts of rapid eye...
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