Why Do We Need Sleep?
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 memory
and 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 by-products 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
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
What Happens When You Sleep?
The Different Stages of Sleep
Source: National Institute of Neurological Disorders and