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Sleep Cycles

Whether one is awake or asleep, the brain emits electrical waves. These waves occur in predictable sleep cycles that can be measured with an electroencephalograph, known more commonly as an EEG. During wakefulness, the waves are recorded at about ten small waves per second, but with the onset of sleep, the waves become larger and slower. The largest, slowest waves occur during the first three hours of sleep when mental activity slows down but does not stop. (A) (I)

In fact, if awakened from slow-wave sleep, a person can often remember vague thoughts that occurred during that period of sleep, but the sleeper does not generally dream. Referred to as NREM or non-REM sleep, it is characterized by large, slow waves. During sleep, intervals of small, fast waves also occur in patterns similar to those experienced while awake. (B) The eyes move rapidly, and it appears to the observer that the sleeper is watching some event. Sleepers who are awakened during this rapid-eye-movement sleep will often recall the details of dreams they have been having. Sleep of this kind is called dreaming sleep or rapid-eye-movement sleep, also known as REM sleep. (II)

REM sleep is emotionally charged. The heart beats irregularly, and blood pressure may be elevated. In contrast, the body is so still that the dreamer may appear to be paralyzed. In a period of eight hours, most sleepers experience from three to five instances of REM sleep. (C) Each instance lasts from five to thirty minutes with an interval of at least ninety minutes between each one. Later instances of REM sleep are usually of longer duration than are instances earlier in the eight-hour period. (III)

Since people who suffer sleep deprivation experience fatigue, irritability, and loss of concentration, we must conclude that sleep is essential because in some way it regenerates the brain and die nervous system. NREM sleep increases after physical exertion, whereas REM sleep tends to increase after a stressful day. (D) Studies suggest that non-REM sleep may be especially helpful in restoring muscle control, whereas REM sleep may be more important in revitalizing mental activity. It appears that both kinds of sleep are necessary, and the recuperation of sleep of one kind will not compensate for a lack of the other kind of sleep. (IV)

[question text="What is the author’s main purpose in the passage? " answers=" *To describe REM sleep#To explain sleep deprivation#To discuss the two types of sleep#To recommend an increase in the number of hours of sleep "]

[question text="How many times per night do most sleepers experience REM sleep? " answers=" Eight#*Three to five#Five to thirty#Ninety "]

[question text="The word “vague” in paragraph II could best be replaced by " answers=" familiar#*indefinite#unpleasant#detailed "]

[question text="The word “essential” in paragraph IV could best be replaced by " answers=" planned#natural#interesting#*necessary "]

[question text="The word “it” in paragraph IV could best be replaced by " answers=" deprivation#the brain#*sleep#concentration "]

[question text="Where in the passage does the author explain why sleep is essential? " answers=" Lines A#Lines B#Lines C#*Lines D "]

[question text="What does the author mean by the statement in paragraph IV: “Studies suggest that non-REM sleep may be especially helpful in restoring muscle control, whereas REM sleep may be more important in revitalizing mental activity”? " answers=" REM sleep is more important than slow-wave sleep for all types of activities.#Mental and physical activities require both kinds of sleep.#Slow-wave sleep, also called REM sleep, restores mental activity.#*Physical activity is supported by slow-wave sleep, but mental activity is supported by REM sleep. "]

[question text="Which response is NOT typical of REM sleep? " answers=" Irregular heartbeat#Dreams and visions#*Movements in arms and legs#Higher blood pressure "]

[question text="The author mentions all the following as characteristics of REM sleep EXCEPT " answers=" *vague thoughts#smaller brain waves#eye movements#dreams "]

[question text="It can be inferred from the passage that students who are writing term papers " answers=" require slow-wave sleep to increase mental activity#can stay up all night working and recover the sleep they need by sleeping for a few hours the next afternoon#*need REM sleep to restore mental functioning#do not need as much sleep because of the heightened brain waves involved in creative activity "]

 

 

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