Disturbances in the normal coordination of light and darkness with wakefulness and sleep account for the temporary sleep disturbance of jet lag or the chronic disorders experienced by many shift workers. The daily cycles of light and darkness help set the body's internal clock. Melatonin, the "dark hormone," is produced by the brain's pineal gland during the night. Testosterone production peaks in the morning, growth hormone at night. Hormone levels also fluctuate cortisol secretion is highest during the morning. Similarly, sodium excretion and urine output are normally higher during the day than at night. For example, normal body temperature is lowest at about 5 a.m., when it averages 97° F, and highest at about 5 p.m., when it averages 99.4° F. Many other bodily functions also wax and wane cyclically in response to the 24-hour circadian rhythm. The sleep-wake cycle is controlled by the body's internal clock. Work hours for medical trainees are now strictly limited. Rest assured, whether you are a patient or on the roads, that corrective action has been taken. But even if overworked interns are not hazardous to their patients, they are hazardous to themselves: a 2005 Harvard study found that extended work shifts are linked to falling asleep at the wheel and having car crashes and near-crashes. Several studies suggest that sleep deprivation is linked to impaired clinical performance, though others show that young doctors can rise to the occasion and solve clinical problems. Medical interns and residents work long hours they have reduced time to sleep, and what sleep they get is often interrupted by medical calls. Whatever the cause, sleep deprivation has predictable consequences, including daytime somnolence, depression and irritability, impaired concentration and judgment, and diminished performance both on the job and off. Shift work is one example of a situation in which people who are capable of sleeping well are unable to get the sleep they need. Insomnia deprives men of restorative sleep, but there are many other causes of sleep deprivation. Sleep requirements change during the course of a lifetime most children need more sleep, most older adults, less. Still, most middle-aged people function best on seven to nine hours of sleep, while others need up to 11 hours. There is no "normal" amount of sleep what matters is how well, not how long you sleep. The two states continue to alternate, with four to six 90- to 110-minute cycles occurring during the course of a typical night's sleep. The sympathetic nervous system is active, stimulating production of adrenaline, the "stress hormone." Most men develop penile erections during REM sleep.Īfter about 30 to 45 minutes, sleep shifts back from REM to the non-REM pattern. Although the body is entirely relaxed, the heart rate and blood pressure fluctuate from low to high the heart pumps less blood to the body but more to the brain. But the brain is turned on dreaming occurs only during REM sleep. Breathing is very slow and may even pause briefly. In contrast, the limb muscles are completely limp and immobile. Although the eyes remain closed, they move rapidly in all directions. The muscles are relaxed, but body movements do occur.Īfter about 45 to 60 minutes, sleep shifts into its REM phase. The circulation slows, too, as the heart rate and blood pressure fall. During non-REM sleep, the mind slows down. They enter non-REM sleep first, moving gradually from light sleep (Stage 1) to deep sleep (Stage 4). Good sleepers fall asleep quickly, usually in less than 15 minutes. Sleep is divided into two major phases, rapid eye movement (REM) sleep and non-rapid eye movement (non-REM) sleep. But although it's restful, sleep is actually quite complex and busy in its own right. Sleep is essential for health, providing rest and restoration for mind and body. Fortunately, lifestyle changes and behavioral treatment can help many sufferers, and medication is available for those who need it. A lucky few get relief from counting sheep, watching late-night movies, or sipping warm milk (or something stronger) - but most people with insomnia need more assistance. But for many men, it's a nightly struggle. Nearly everyone has spent at least one night lying in bed wishing for sleep.
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