(Transition Statement) Understanding the sleep cycle is the first part of understanding dreams and how dreams happen. The average human being spends eight hours a day, fifty-six hours a week, two hundred twenty-four hours a month, and two-thousand, six hundred eighty-eighty hours a year sleeping.
I. (First Main Point) Sleep is divided into two main blocks: NREM sleep and REM sleep.
A. When we sleep, we go through five stages lasting approximately 90-120 minutes, repeating itself several times throughout the night.
1. We first experience Non-Rapid Eye Movement, or (NREM) sleep, which can be divided into four stages.
a. Stage 1 - Very light sleep, in which it is easy to wake up
Stage 2 - Slightly deeper sleep
Stages 3/4 - Our deepest sleep
b. Our brain activity through these stages gradually slow down, so that by deep sleep - we experience our slowest brain waves.
c. About 90 minutes after we go to sleep and after the fourth sleep stage, we begin REM sleep.
2. Rapid-Eye Movement, or (REM) sleep is the final stage of our sleep cycle.
a. During REM sleep several physiological changes take place.