| The amount of sleep
an individual requires varies from person to person, but most
adults average eight hours of sleep.
 Sleep plays a vital role in our daily
regimen, as during this dormant period, it recharges
and rejuvenates weary body organs and tissues, and
restores the body to an alert state. A person's lifestyle is
another variable in the amount of time he needs to achieve
this healthy balance, and to feel well rested upon
awakening.
The quality of a person's sleep also factors into the sleep
equation. When we drift off to sleep, we either fall into a
deep, restful sleep, or into a shallow, light sleep. One who
normally requires eight hours of sleep, but sleeps shallowly,
will most likely awaken feeling tired. In contrast, if the
same individual sleeps fewer hours, but lapses into a state of
deep sleep, he may well awaken refreshed and
invigorated.
A lucky few can bypass shallow sleep altogether, and fall
directly into deep sleep on an as needed basis. Alexander the
Great's military prowess may have been due, in part, to
his ability to take a "cat nap."
Yet one more variable factors into the amount of sleep we
require: that of the brain and of the body sleeping
simultaneously. Under normal circumstances, the brain's sleep
center blocks off the nerves to the brain and to the body to
make sleep possible. The brain has no interest in doing
anything, and could not even if it did, because the sleep
center has shut down the internal organs, the arms, and the
legs. Sometimes, however, the sleep center is unsuccessful in
shutting down both the brain and the body at the same time.
For example, in times of war, it is not unusual for soldiers
suffering from sleep deprivation and from combat
fatigue to continue to march, despite the fact that their
brains have halted. Thankfully, such a situation is an
anomaly, and does not occur with great
frequency. |
regimen: 生活制度
rejuvenate:使恢復,使年輕
invigorated:精神煥發(fā)的
prowess:威力
deprivation:剝奪
anomaly:不正常的 |
