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Many modern investigators have done research in the field of sleep and their conclusions have
often differed extensively. Yet they all have agreed on one point: sleep is nature's great restorer.
Sleep induces such aspects as absence of voluntary motion, loss of awareness and the harsh
sounds that we call snoring. There are also changes in metabolism, in the pulse rate, in blood
pressure, in bodily temperature, in nerve functions and in the nature of bodily reflexes. Sleep is
characteristic of both plant and animal life. There were several theories at the start of the
present century to answer the question "Why do we sleep?". According to one of them,
nerve cells shrank throughout waking hours so we couldn't make contact with other people any
more and became sleepy. Another theory was that some sort of toxin accumulated during
waking hours. In time, this toxin would affect the nervous system so that it would slow down.
According to the most widely accepted explanation-the so
called "cerebral-anaemia" theory-sleep was brought about because the blood supply to the brain
diminished. However, today we know that none of these theories were valid. For instance, it has
been proven that the blood supply to the brain increases during sleep. This is accurately the
opposite of "cerebral-anaemia" theory. In fact, this increased circulation has a restorative value.
What are some disorders of sleep? Somnambulism is very common. About 40% of university
students talk in their sleep. When they wake up, they don't remember anything. Another
disorder, somnambulism, is
not so common. You may have seen people walking while they are sleeping. This may result
from an emotional disturbance and the person again doesn't remember anything when he wakes
up. Muscle cramps sometimes disturb sleep as well. (Of course they may also occur when one
is awake.) Insomnia, or inability to go to sleep is one of the most common conditions about
which adults should consult a doctor. Some are temporary; however, others should need
psychological treatment. Sleeping sickness is another serious disorder. It is usually long-lasting
and may cause death.
13. “accumulated” refers to
a) appeared
b) plunged
c) increased
d) disappeared
14. Which of the following may come out if a person is emotionally disturbed?
a) Sleeping sickness
b)
Somnambulism
c) Muscle cramps
d) Sleep-talking
15. Which of the following is not a feature of sleep?
a) Changes in the pulse rate
b) Absence of voluntary motion
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