Friday, December 11, 2009

Stages of Sleep

Sleep is often some lucky people's best friend, while, there are people who yearn to befriend sleep.  I remember watching Insomnia, an Al Pacino movie, where he suffers from insomnia. All I can say is that it was a very well done movie. Whether there is a physical, mental or  an emotional problem, one of the body's natural reaction is an affected sleep. So while I took psychology 101, I studied about sleep. I dont want to write too much in detail here, but instead I just want to talk about stages of sleep in real simple terms.

So basically sleep can be broadly categorized into two types: 
  1. Non-Rapid Eye Movement (NREM)
  2. Rapid Eye Movement (REM)

Thanks to invention of EEG and other such devices which have helped in studies about sleep.  During each stage of sleep, the brain produces waves which have been studied to identify the various stages of sleep.
Sleep firstly begins with the brain producing beta waves, and you will be pretty much close to awake and alert. As the brain begins to relax and slow down, slower waves known as alpha waves are produced. During this stage we do experience certain hallucinations.- hypnagogic hallucinations to be precise. I will be talking in detail about hallucinations in a different post. People also have what is known as a myoclonic jerk.

Stage 1-NREM

Stage 1 sleep is the beginning stage of sleep. In Stage 1, the brain produces theta waves. This period of sleep lasts only around 5-10 minutes.

Stage 2-NREM

Stage 2 is the second stage of sleep and lasts for approximately 20 minutes.  During this stage, the brain begins to produce bursts of rapid, rhythmic brain wave activity known as sleep spindles. Body temperature starts to decrease and heart rate begins to slow.

Stage 3-NREM

Deep, slow brain waves known as delta waves begin to emerge during stage 3 sleep. It is during this stage, that body tends to get into a deep sleep.

Stage 4-NREM

Stage 4 is a deep sleep that lasts for approximately 30 minutes. Stage 4 is sometimes referred to as delta sleep because of the slow brain waves known as delta waves that occur during this time.

Stage 5 - REM

The 5th stage of sleep is known as rapid eye movement (REM) sleep. During this stage, there is eye movement, increased respiration rate, increased brain activity. REM sleep is also referred to as paradoxical sleep because while the brain and other body systems become more active muscles become more relaxed. Dreaming occurs due because of increased brain activity, but voluntary muscles become paralyzed.

Sleep basically occurs in cycles. Sleep begins in stage 1 and progresses into stages 2, 3, and 4. After stage 4 sleep, stage 3 and then stage 2 sleep are repeated before entering REM sleep. Once REM sleep is over, the body usually returns to stage 2 sleep. Sleep cycles through these stages approximately 4 or 5 times throughout the night. REM Sleep in itself is a vast topic and there a lot of funny phenomenon which we do experience once we are out of REM sleep, and I must say it is beyond the scope of this post ;).

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