about 90 minutes after you fall asleep. The table below summarizes the difference in the processes that occur during the sleep cycle. Table 1. Comparison of Physiological Changes During NREM and REM Sleep Physiological During NREM During REM Process increases in motor and sensory brain activity decreases from wakefulness areas, while other areas are similar to NREM increases and varies compared heart rate slows from wakefulness with NREM increases (up to 30 percent) and blood pressure decreases from wakefulness varies from NREM increases by 50 to 200 percent blood flow to does not change from wakefulness from NREM, depending on brain brain in most regions region increases and varies from NREM, respiration decreases from wakefulness but may show brief stoppages (apnea); coughing suppressed airway increases and varies from increases from wakefulness resistance wakefulness is regulated at lower set point than is not regulated; no shivering or body wakefulness; shivering initiated at sweating; temperature drifts temperature lower temperature than during toward that of the local wakefulness environment increases from NREM (in both sexual arousal occurs infrequently males and females) () Additional information on details of the function of the endocrine and renal systems and alimentary activity can be found at the National Institutes of Health Teacher’s Guide (see the URL above). Studies on rats show that their normal life spans of two to three years have been shortened to five months when they are deprived of REM (see section below on sleep). When deprived of all sleep, they may die in as little as three weeks. Some scientists consider lack of sleep as injurious to health as lack of food. () More on the quality of sleep and the NREM/REM cycles It is not only the nine hours of sleep before the alarm that are important for teens, but it is also the adequate quality of this sleep time that is required to produce a refreshed and alert morning wake up. There are four main stages of sleep: The Stages of Sleep
about 90 minutes after you fall asleep. The table below summarizes the difference in the processes that occur during the sleep cycle. Table 1. Comparison of Physiological Changes During NREM and REM Sleep Physiological Process During NREM During REM brain activity decreases from wakefulness increases in motor and sensory areas, while other areas are similar to NREM heart rate slows from wakefulness increases and varies compared with NREM blood pressure decreases from wakefulness increases (up to 30 percent) and varies from NREM blood flow to brain does not change from wakefulness in most regions increases by 50 to 200 percent from NREM, depending on brain region respiration decreases from wakefulness increases and varies from NREM, but may show brief stoppages (apnea); coughing suppressed airway resistance increases from wakefulness increases and varies from wakefulness body temperature is regulated at lower set point than wakefulness; shivering initiated at lower temperature than during wakefulness is not regulated; no shivering or sweating; temperature drifts toward that of the local environment sexual arousal occurs infrequently increases from NREM (in both males and females) () Additional information on details of the function of the endocrine and renal systems and alimentary activity can be found at the National Institutes of Health Teacher’s Guide (see the URL above). Studies on rats show that their normal life spans of two to three years have been shortened to five months when they are deprived of REM (see section below on sleep). When deprived of all sleep, they may die in as little as three weeks. Some scientists consider lack of sleep as injurious to health as lack of food. () More on the quality of sleep and the NREM/REM cycles It is not only the nine hours of sleep before the alarm that are important for teens, but it is also the adequate quality of this sleep time that is required to produce a refreshed and alert morning wake up. There are four main stages of sleep: The Stages of Sleep
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