9. Stages of sleep

There are 5 stages of sleep.  The first stage is referred to as light sleep. During the first stage of sleep, muscle activity is lowered and people can be easily awakened from stage 1 sleep. The next stage is stage 2 sleep. In stage 2 sleep the breathing pattern and heart rate slow down. We spend most of our time sleeping in stage 2 sleep.  During stage 3 the brain produces delta waves. Breathing and heart rate go to their lowest level.  During stage 4 there is rhythmic breathing and very limited muscle activity. Stage 5 of sleep is known as REM (Rapid Eye Movement) sleep.  You lose consciousness during REM sleep.  You dream during this period of REM sleep. Also, your body becomes paralyzed all of your limbs lock in place. Your breathing rate and blood pressure rise as well.  During REM sleep your eyes move very rapidly back and forth under your eyelids. This is how the name REM was derived.