Today we are less dependent on sun-to-sun lighting cycles, although many scientific experiments have shown people are still genetically hard-wired and exquisitely attuned to the natural cycles of day-and-night throughout the seasons.
Nevertheless, we can exert far more control on our periods of sleep and wakefulness than could previous generations.
The ability to easily control sleep periods, by itself, can cause problems if any of a multitude of distractions crop up to interfere with sleep. However, the ability to control also creates powerful opportunities to address those distractions.
In the STS you will soon leverage these powerful opportunities to control – by learning how to create an optimal environment for restful, quality sleep.
Stages of Sleep
Sleep is far more than just an unconscious mental state. Sleep researchers have determined that several stages of sleep with varying amounts of physical and mental activity occur predictably each night. These stages of sleep have been extensively studied, and are divided into two main types –
Rapid Eye Movement (REM) sleep, and
Non-Rapid Eye Movement (NREM) sleep.
REM sleep is characterized by tiny back-and-forth movements in the eye, and typically are accompanied by the visual and emotional world of vivid dreams. The eyes move in tandem, as they do normally during an awakened state. The tiny muscles in our inner ears move as if we're hearing, even in complete silence. REM sleep typically comprises about 20-25% of sleep for most adults, although that percentage declines somewhat as we age. All of us dream, even though we may not remember the dreams.
REM sleep makes it appear as if we are watching and listening to what’s going on as we dream. Some scientists believe that the eye movements of REM sleep relate to the visual images of dreams, but why they exist and what function they serve, if any, remain unknown.
REM sleep includes very active brain activity, and if awakened during REM sleep many people will vividly remember their dreams. Our bodies are also much more active during REM sleep, with a higher heart rate, breathing, and blood pressure than during deep sleep. REM sleep is also characterized by a natural form of muscle paralysis, although this is the sleep phase when males often experience an erection, and females experience clitoral engorgement.