6 Salient Sleep Specifics

1.  Sleep is essential to survival. It is the third arm in the triangle of health that also includes diet and exercise.  During sleep, several neurons have the opportunity to shut down and repair themselves while the brain may also exercise other neuronal connections that would deteriorate without this periodic activity.  Areas responsible for social and emotional functioning also shut down during sleep.  There is a reduction in the breakdown and an increase in the production of protein, a major building block of the body.  It is also believed that memories are encoded in the brain at this time.  All of these activities demonstrate the restorative nature of sleep for our physical and mental health.

2.  Sleep is cyclical.  The regular changes in our mental and physical characteristics that occur over the course of a (24-hour) day constitute circadian rhythm.  This rhythm is controlled by a region of the brain called the suprachiasmatic nucleus (SCN) which lies close to where the optic nerves cross.  Photoreceptors (or nerve cells specialized to sense light) send signals from this area  to the SCN.  As a result our Circadian Rhythm is strongly tied to the sunlight.  This means we were truly designed to sleep during the night.  In addition, the activity of sleep itself is also characterized by a 5-stage cycle that generally lasts from 90 to 110 minutes and repeats throughout an 8-hour (on average) period of sleep.  Generally, through the course of any given night we move from stage 1 or light sleep into stage 2 followed by the restorative deeper sleep of stage 3 and stage 4 and finally REM (rapid eye movement) stage.  The entire cycle lasting just under 2 hours but repeating three or four more times before morning.

3. Sleep is dynamic.  Sleep studies in which an individual is monitored with an EEG (electroencephalogram) which measures brain activity as they sleep have shown us that the sleep is characterized by several distinct brain waves.  During stage 2 slowed brainwaves are interrupted by occasional burst of rapid waves called sleep spindles.  During stage 3, the extremely slow brain waves called delta waves are interrupted by smaller faster waves until stage 4, which is characterized exclusively by delta waves.  Finally, the onset of REM brings rapid jerking of the eyes in various directions and the phenomenon we call dreaming.

4. Sleep deprivation is dangerous.  It not only impairs memory, but can also affect hand-eye coordination sometimes more severely than alcohol. Prolonged sleep deprivation can compromise the immune system leading to an overall decline in physical health.

5. Sleep is sensitive to drugs. Many antidepressants suppress REM sleep. caffeine, decongestants and appetite suppressants all stimulate parts of brain that cause insomnia. The depressant character of alcohol will allow light sleep but robs people of REM and deep sleep.  Heavy smokers generally awake four hours into their sleep cycle due to nicotine cravings.

6. Sleep and coma are not the same.  While sleep is characterized by lots of electrical activity from complex active brain wave patterns, a comatose person or someone under anesthesia has very slow and weak brain waves, sometimes nearly imperceptible.

Source: National Institute of Neurological Disorders and Stroke
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