The chemical adenosine is released by brain cells when those cells are active. Adenosine then binds to more and more sites on cells in certain areas of the brain, as the total amount released gradually increases during wakefulness. During sleep, the number of sites to which adenosine is bound decreases. Some researchers have hypothesized that it is the cumulative binding of adenosine to a large number of sites that causes the onset of sleep.
Which of the following, if true, provides the most support for the researchers’ hypothesis?
A. Even after long periods of sleep when adenosine is at its lowest concentration in the brain, the number of brain cells bound with adenosine remains very large.
B. Caffeine, which has the effect of making people remain wakeful, is known to interfere with the binding of adenosine to sites on brain cells.
C. Besides binding to sites in the brain, adenosine is known to be involved in biochemical reactions throughout the body.
D. Some areas of the brain that are relatively inactive nonetheless release some adenosine.
E. Stress resulting from a dangerous situation can preserve wakefulness even when brain levels of bound adenosine are high.作者: a10285 时间: 2009-12-5 18:01
题目的逻辑结构是 清醒时Adenosine bind的范围逐渐增加，睡眠时Adenosine bind的范围减少，结论是Adenosine bind的范围的累积增加导致睡眠， 而B说Caffeine，能让人保持清醒，已知能干扰Adenosine bind（隐含Adenosine bind的范围的不能累积增加）验证了理论到实践的过程作者: keaneice 时间: 2009-12-5 22:15
文章结论：A的高浓度引起睡眠。 A/ 削弱 （举反例，说就算刚睡醒，浓度也高） B/ 加强。 破坏了A的binding，就不会困 C/ 与题目无关 D/ 与题目无关 E/ 特列，一般不作为参考。（即使可以接受，也是削弱）