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The Sleep Cycle

Hi everyone!

Last week I wrote about the REM stage in the sleep cycle. But I realized not many people (me included) understand what the other cycles even are. So today’s blog post is all about the non-REM stages of sleep.

There are five total sleep stages, the fifth being REM sleep. The first four are often referred to as non-REM stages. There has been some controversy as to whether the non-REM stages actually consist of fourth distinct stages. Some believe the third and fourth should just be combined into a third and final stage of non-REM sleep and others argue that the third and fourth are unique stages and should be kept separate. This blog post follows the latter and goes by the five-stage sleep cycle, that of which having four separate stages in the non-REM sleep stages.

Stage One: This stage lasts under ten minutes. This time period is considered to be the transition between being awake and sleeping.  In this stage the brain forgoes “Alpha Waves” and sends high amplitude “Theta Waves”, which are very slow moving brain waves.  During this time, muscle contractions (hypnic myoclonia, or hypnic jerks) can cause the feeling of falling.

Stage Two: This stage is about 20 minutes and it is the time when your body is preparing itself for a deep sleep.  No eye movement occurs in this stage and dreaming is not common, in fact it is quite rare. Your body slows the heart rate and lowers your overall body temperature. This is the stage where the brain has rapid, rhythmic brain activity referred to as sleep spindles.

Stage Three:  This is the transitional period between light and deep sleep, when slow-moving “Delta Waves” come into play. Dreaming is common in this non-REM stage, where it is not as common in the previous two stages.

Stage Four: This stage lasts about 30 minutes. “Delta Waves” are flowing in this stage just like in Stage Three. Dreaming is also common in this stage and if a person is woken up at this time, they may be unsure of their surroundings for a little while. Toward the end of this stage is when sleepwalking happens.

Throughout the night these stages repeat, along with the REM Stage, and form the sleep cycle as we know it.

Hope this helps!

~Nadette

 

Sources:

http://en.wikipedia.org/wiki/Non-rapid_eye_movement_sleep

http://psychology.about.com/od/statesofconsciousness/a/SleepStages.htm

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