Different Stages of Sleep Cycle
Many people have no clue what the body and mind are up to when they fall asleep. Obviously, you are resting when you sleep, but this is not true for all parts of your body. The brain remains quite active, and continues to send various signals out that control the different stages of sleep. Other changes in activity include eye movement and muscle activity.
There are five documented stages of sleep, and you will experience all of them more than once during a good night of sleep. The first four of these stages can all be categorized as non-rapid eye movement sleep, or NREM. REM, or rapid eye movement sleep is the fifth stage.
Differences in brain wave activity are what determine the different stages of sleep. Several other conditions, including irregular and rapid breathing, rapid heartbeat, increased blood pressure, increased brain activity, and limited muscle activity are also indicators of REM sleep.
During any given sleep period, all stages of sleep will take place. NREM sleep is usually experienced during the first third of the night, while the third third of the night usually consists of REM sleep. It is usually REM sleep that you awaken from.
Stage 1 is a light transitional sleep that you can be easily awakened from. It is during this stage that you may find yourself waking up and falling asleep several times. This is the time when you begin to to feel sleepy. Your eye movement will begin to slow and you experience decreased muscle control. You may also experience some muscle jerking, which is also referred to as hypnic myoclonia.
Around half of the sleep period will be occupied by stage 2. In this stage, the brain waves will slow down and the eyes will stop moving. Body temperatures and heart rates will also slow during this time. There may, however, be sudden bursts of eye movement.
Stages 3 and 4 are what are known as a deep sleep. In addition to no movement of the muscles and eyes, the brain is at a low level of activity as well. This is characterized by extremely slow delta brain waves.
REM sleep will be experienced at different times throughout the sleep period. This type of sleep consists of about on quarter of the time spent sleeping and always follows a period of NREM sleep. The first occurrence of REM lasts about 10 minutes and happens at the end of Stage 1. The final period of REM lasts for about one hour. REM will be experienced 4 or 5 times during a typical 8 or 9 hour sleep period. Dreams will also happen during REM.
This repetition of sleep stages is commonly known as sleep cycles. During any given sleep period, these cycles can be experienced several times. As these cycles progress further into the sleep period, more time is spent in REM sleep. The best quality sleep takes place when there is limited interruptions in the cycles.
Intro to Sleeping Well
How Much Sleep Do We Need
Circadian Rhythm and Sleep
Melatonin and Sunlight
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