WHAT IS SLEEP?
Sleep is defined as a state of unconsciousness from which a person can be aroused.
SLEEP AND ARISTOTLE
The Greek philosopher Aristotle actually came up with the first scientific theory of sleep in 350 B.C. He wrote, “A person awakes from sleep when digestion is complete.” This turned out to be untrue, but science wouldn’t refute that for another 2000 years.
CIRCADIAN RHYTHMS
In 1729 a French astronomer identified our biological rhythms by tracking stars. As misguided as it was, it led the way for the study of the Circadian clock that controls our sleep cycles. This is an internal time-keeping device that the human brain uses to control body temperature and release certain chemicals at the right time. The fact that Circadian rhythms exist tells us that regular sleep is essential to human (and animal) survival.
FOUR THEORIES OF SLEEP
For Resting: To gain relief from the hyperactive state of being awake during which our bodies grow and repair the immune and nervous systems, as well as our muscles and bones.
For Healing: Sleep deprivation affects our immune system and our metabolism. Our body uses sleep to help keep these systems functioning properly and saves energy for when we most need it.
For Learning: Sleep experiments have shown that our ability to perform certain skills is dependent on REM sleep. Similarly, our knowledge of facts relies on Slow Wave Sleep.
For Dreaming: Dreaming appears to be a by-product of REM sleep. We still don’t know why we dream. It could be a result of random impulses, to organize the brain, to help solve problems, or to cope with trauma.
THE STAGES OF SLEEP
Stage 1: Light Sleep Brainwave frequencies descend from waking alpha waves to drowsy theta waves. Muscle activity slows causing twitches and jerks. You begin to lose self-awareness.
Stage 2: Light Sleep Eye movement stops and brain waves become slower. You lose nearly all muscle tone.
Stage 3 and 4 : Deep Sleep Extremely slow delta brainwaves are interspersed with smaller, faster waves. It is very difficult to waken someone from this stage. There is no eye movement or muscle activity. This is the stage where sleepwalking occurs.
REM Sleep: Brainwave frequency jumps to highly active beta waves during three to five intervals per night. You have bursts of Rapid Eye Movement and muscle twitches. The most vivid dreams happen during REM sleep. REM sleep represents 20-25% of the total sleep time.