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  3. Late-night Drinking Coffee lovers beware. Having a quick "pick-me-up" cup of coffee late in the day will play havoc with you sle

Late-night Drinking Coffee lovers beware. Having a quick "pick-me-up" cup of coffee late in the day will play havoc with you sle

admin2009-06-15  13
问题                     Late-night Drinking
Coffee lovers beware. Having a quick "pick-me-up" cup of coffee late in the day will play havoc with you sleep. As well as being a stimulant, caffeine interrupts the flow of melatonin, the brain hormone that send people into a sleep.
Melatonin levels normally start to rise about two hours before bedtime. Levels then peak between 2 a.m. and 4 a.m., before falling again. "It’s the neurohormone that controls our sleep and tells our body when to sleep and when to wake," says Manrice Ohayon of the Stanford Sleep Epidemiklogy Research Center at Stanford University in California. But researchers in Israel have found that caffeinated coffee halves the body’s levels of this sleep hormone.
Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six volunteers slept less well after a cup of caffeinated coffee than after drinking the same amount of decaf. On average, subjects slept 336 minutes per night after drinking caffeinated coffee, compared with 415 minutes after decaf. They also took half an hour to drop off--twice as long as usual-- and jigged around in twice as much.
In the second phase of the experiment, the researchers woke the volunteers every three hours and asked them to give a urine sample. Shilo measured concentrations of a breakers were half those in decaf drinkers. The results suggest that melatonin concentrations in caffeine drinkers were half those in decaf drinkers. In a paper accepted for publication in Sleep Medicine, the researchers suggest that caffeine blocks production of the enzyme the drives melatonin production.
Because it can take many hours to eliminate caffeine from the body, Ohayon recommends that coffee lovers switch to decal after lunch.
选项 A、melatonin levels need to be raised
B、neurohormone can wake us up
C、coffee is stimulant
D、decaf is a caffeinated coffee
答案C
解析 利用题干中的核心结构(也是特殊结构)“pick-me-up”作为答案线索，找到答案相关句：Coffee lovers beware(谨慎)．Having a quick“nick-me-up”cup of coffee late in the day will play havoc with you sleep.(暗示咖啡影响睡眠)As well as being a stimulant(刺激物)，(该划线句说“咖啡因作为一种刺激物……”，因此可以得出结论“咖啡是一种刺激物”，C是答案)caffeine interrupts the flow of melatonin(褪黑激素)，the brain hormone that send people into a sleep．
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