Sleep, is a normal state of relaxation and is identified by less body movement and reduced awareness of surroundings. Sleep is a different from other sleeplike states, for example, hibernation or coma, because it gets disturbed easily external stimulation, such as a loud noise. While the exact purpose of sleep remains a mystery, sleep researchers have made enormous strides in understanding how sleep occurs in humans and other animals, and the nature of sleep disorders. In the 1950s American physiologists Eugene Aserinsky and Nathaniel Kleitman reported that periods of eye movement and twitching occur during sleep.( Mougin, F., Simon-Rigaud, M. 1991) They named these periods rapid eye movement (REM) sleep. Aserinsky and Kleitman found that when subjects were awakened during REM sleep, they reported vivid dreams. Scientists believe that REM sleep is closely related to wakefulness because brain wave activity during REM sleep is marked by short, rapid wave patterns similar to brain wave activity of the waking state. Sleep characterized by little or no eye movement is called nonrapid eye movement (NREM) sleep.( Mougin, F., Simon-Rigaud, M. 1991) During NREM sleep, breathing and heart rates slow down, and body temperature and blood pressure often decrease. When awakened from periods of NREM sleep, subjects are much less likely to report vivid, action-packed dreams.
Sleep is as important to the human body as food and water, but most of us don't get enough sleep. Insufficient sleep or disruptions to the sleep-wake cycle (such as those that occur with shift work or traveling to a different time zone) cause the physiological state known as fatigue. A fatigued person is accident prone, judgment impaired and more likely to make mistakes and bad decisions.( Pierce, E., McGowan,R., Barkett, E., Fry, R. 1993) Staying awake for 24 hours leads to a reduced hand-to-eye coordination which is similar to having a blood alcohol content of 0.1................
