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Although scientists are still trying to learn exactly why people
need sleep, animal studies show that sleep is necessary for
survival. For example, while rats normally live for two to three
years, those deprived of REM sleep survive only about 5 weeks on
average, and rats deprived of all sleep stages live only about 3
weeks. Sleep-deprived rats also develop abnormally low body
temperatures and sores on their tail and paws. The sores may
develop because the rats' immune systems become impaired. Some
studies suggest that sleep deprivation affects the immune
system in detrimental ways.
Sleep appears necessary for our nervous systems to work
properly. Too little sleep leaves us drowsy and unable to
concentrate the next day. It also leads to impaired memoryand physical performance and reduced ability to carry out
math calculations. If sleep deprivation continues,
hallucinations and mood swings may develop. Some
experts believe sleep gives neurons used while we are awake a
chance to shut down and repair themselves. Without sleep, neurons
may become so depleted in energy or so polluted with byproducts of
normal cellular activities that they begin to malfunction. Sleep
also may give the brain a chance to exercise important neuronal
connections that might otherwise deteriorate from lack of
activity.
Deep sleep coincides with the release of growth hormone
in children and young adults. Many of the body's cells also show
increased production and reduced breakdown of proteins during deep
sleep. Since proteins are the building blocks needed for cell
growth and for repair of damage from factors like stress and
ultraviolet rays, deep sleep may truly be "beauty sleep."
Activity in parts of the brain that control emotions,
decision-making processes, and social interactions is drastically
reduced during deep sleep, suggesting that this type of sleep may
help people maintain optimal emotional and social
functioning while they are awake. A study in rats also showed
that certain nerve-signaling patterns which the rats generated
during the day were repeated during deep sleep. This pattern
repetition may help encode memories and improve learning.
National Institutes of Health
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