Stages of Sleep

The stages in your sleep cycle are organized by the changes in specific brain activity.

STAGE 1:

• Light Sleep
• Non-rapid eye movements
• (NREM) 
• Muscle relaxation
• Lowered body temperature 
• Heart rate slows down

Your body is preparing to enter a deep sleep. 

STAGE 2:

• (NREM)
• Body temperature decreases more 
• Relaxation of the muscles decrease more as well
• Immune system works on repairing the day's damage
• Endocrine glands - secrete growth hormones (Put hormones in the blood)
• Blood is sent to the muscles to recondition 

You are now completely asleep. 

STAGE 3:

• (NREM) 
• Deeper sleep

STAGE 4:

• Eyes move back and forth erratically (Like you're watching something from underneath your eyelids)
• REM SLEEP - 90-100 minutes after you fall asleep
• Blood pressure rises
• Heart rate speeds up 
• Breathing increases
• Brain activity increases
• Involuntary muscles become paralyzed 
• Your emotions are being tuned and played with

Dreaming usually occurs in this stage, and if you wake up during this stage then you will most likely remember your dreams or most of them. 

These 4 stages repeat themselves during the night as you sleep. 

While they repeat, you will spend less time in stages 1, 2 & 3 and most in 4.

http://www.dreammoods.com/dreaminformation/dreamresearch.htm