Sleep has 2 main phases: rapid eye movement (REM) sleep and non-rapid eye movement (non-REM) sleep.
When you are in non-REM sleep, you go through 4 stages. During stage 1, you are in transition between being awake and asleep, and wake easily. During stages 2, 3 and 4, your eye movements stops, your body temperature falls, and you are deeply asleep.
In REM sleep, your eyes move rapidly, your blood pressure and heart rate go up, and your brain becomes very active. REM sleep is when most dreaming happens, and is thought to be important for learning and creating new memories.
REM sleep happens about every 90 minutes during the night. Adults usually spend about one fifth of the night in REM sleep and the remaining 4 fifths in non-REM sleep. Infants spend at least half of the time they’re asleep in REM sleep.
Information sourced from Health Direct
