Monday, 29 April 2013

Sleep cycle...


The Sleep Cycle 

Sleep Cycle

The Sleep Cycle moves from Stage I to REM then it starts all over again, continuing throughout the night. Most people complete 3 to 5 cycles each night, each cycle lasts from 90 to 110 minutes. Towards the end of sleeping, the individual does not reach stages III or IV as the body prepares to wake up.

Non REM sleep
Stage I
Light sleep
Eye and muscle activity slow
Brain activity decreases by 50%
Individual may experience sudden muscle contractions
On this stage the individual and be easily aroused
Stage II
Eye movement stops
Muscle activity stops
Brain waves slow down
Small burst of brain activity begin (also known as Sleep spindles)
Stage III
Deep sleep Starts
Brain begins to produce slow delta waves
There is no eye or muscle movement
Stage IV
Deep sleep
Brain produces only delta waves
No muscle or eye movement
Hard to awaken
REM sleep
Heart and breathing rates increase
Eye movement is quick and irregular
Blood pressure rises
Breathing becomes shallow
Almost complete loss of muscle control
Penile erections (males) and vaginal moistening (females)
Sleeper begins to dream (more intense, vivid dreams)

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