Read
the passage.
"Oh
sleep! It is a gentle thing,
Beloved
from pole to pole."
Samuel Taylor Coleridge, a famous
British poet, wrote these words over 100 years ago. Most people would agree
with him. Sleep is very important to humans; the average person spends 220,000
hours of a lifetime sleeping. Until about thirty years ago, no one knew much
about sleep. Then doctors and scientists began doing research in sleep
laboratories. They have learned a great deal by studying people as they sleep,
but there is still much that they don't understand.
Scientists study the body
characteristics that change during sleep, such as body temperature, brain
waves, blood pressure, breathing, and heartbeat. They also study rapid eye
movement (REM). These scientists have learned that there is a kind of sleep
with REM and another kind with no rapid eye movement (NREM).
NREM is divided into three stages. In
stage one, when you start to go to sleep, you have a pleasant floating felling.
A sudden noise can wake you up. In stage two, you sleep more deeply, and a
noise will probably not wake you. In stage three, which you reach in less than
thirty minutes, the brain waves are less active and stretched out. Then, within
another half hour, you reach REM sleep. This stage might last an hour and a
half and is the time when you dream. For the rest of the night, REM and NREM
alternate.
Body movement during sleep occurs just
before the REM stage. The average person moves about thirty times during sleep
each night.
Sleep is a biological need, but your
brain never really sleeps. It is never actually blank. The things that were on
your mind during the day are still there at night. They appear as dreams, which
people have been discussing for centuries. At times people believed that dreams
had magical powers or that they could tell the future.
Sometimes dreams are terrifying, but
they are usually a collection of scattered, confused thoughts. If
you dream about something that is worrying you, you may wake up exhausted, sweating,
and with a rapid heartbeat. Dreams have positive effects on our lives. During a
dream, the brain may concentrate on a problem and look for different solutions.
Also, people who dream during a good night's sleep are more likely to remember
newly learned skill. In other words, you learn better if you dream.
Researchers say that normal people may
have four or five REM periods of dreaming a night. The first one may begin only
a half hour after falling asleep. Each period of dreaming is a little longer, the
last one lasting up to an hour. Dreams also become more intense as the night
continues. Nightmares usually occur towards dawn.
People dream in colour, but many don't
remember the colours. Certain people can control some of their
dreams. They make sure they have a happy ending. Some people get
relief from bad dreams by writing them down and then changing the negative
stories or thoughts into positive ones on the written paper. Then they study
the paper before they go to sleep again.
Many people talk in their sleep, but it
is usually just confused half sentences. They might feel embarrassed when
someone tells them they were talking in
their sleep, but they probably did'nt tell any secrets.
Sleepwalking is most common among
children. They usually grow out of it by the time they become adolescents.
Children don't remember that they were walking in their sleep, and they don't
usually wake up if the parent leads them back to back.
There are lots of jokes about snoring,
but it isn't really funny. People snore because they have trouble breathing
while they are asleep. Some snorers have a condition called sleep apnea. They
stop breathing up to thirty or forty times an hours because the throat muscles
relax too much and block the airway.
Most people need form 7½ to 8½ hours of
sleep a night, but this varies with individuals. Babies sleep eighteen hours,
and old people need sleep than younger people. If some continually sleeps
longer than normal for no apparent reason, there may be something physically or
psychologically wrong.
You cannot save hours of sleep the way
you save money in the bank. If you have only 5 hours of sleep for three nights,
you don't need to sleep extra 9 hours on the weekend. And it doesn't do any good
to sleep extra hours ahead of time when you know you will have to stay up late.
Sleep is important to humans. We spend a
third of our lives sleeping, so we need to understand everything
we can about sleep.
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