The REM stage of sleep is the time when dreams occur. This stage is called rapid eye movement because scientists have studied the brain waves of people who are dreaming and have noted that sleepers actually move their eyes back and forth under their eyelids at that time, almost as if they were watching a movie.
The body may release Cortisol in this stage (although cortisol can be released anytime during sleep). Cortisol is a hormone released by the adrenal glands. It controls blood pressure, blood sugar, and other key body functions. Some people with FMS may have overly low levels of cortisol in the daytime, leading to excessive fatigue, and overly high levels at night (causing insomnia). Cortisol production peaks early in the morning, shortly before you awake.
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