TEXT IV
Sleep (slēp):
A natural state of rest, occurring at regular
intervals, in which the eyes usually close, the
muscles relax, and
responsiveness to external events decreases.
Growth and repair of the tissues of the body are
thought to occur duringsleep, and energy is
conserved and stored. In humans and some other
animals, scientists have identified one phase of
sleep (called REM sleep) as the phase in which
dreams occur.
Did You Know? Shakespeare had it right. He
said that sleep was the "balm of hurt minds" and
that sleep "knits up the ravel'd sleeve of care." In
other words, sleep helps overcome the stress of
everyday life. So the third of your life you spend
asleep is not a waste of time. All warm-blooded
animals have the need to sleep. Studies have
shown that animals that are not allowed to sleep
for a long enough time can actually die. Babies,
human and animal, sleep even more than adults
do. Researchers think that babies may sleep so
much because it helps the young body continue to
develop quickly. Not only are babies' bodies
growing, but their brains are, too – and sleep is
very important for the brain. During sleep, the brain
sorts through experiences and stores important
new information for later use. This processing of
experiences, in fact, is thought to be a major
source of dreams.
(Source: The American Heritage® Student Science Dictionary,
Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt
Publishing Company. Published by Houghton Mifflin Harcourt
Publishing Company.)