Sleep cycle...

KNOW  YOUR  SLEEP CYCLE.........

The 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)