考研易错题（2019/7/5）

第1题：已知3阶矩阵A可逆，将A的第2列与第3列交换得B，再把B的第1列的-2倍加至第3列得C，则满足PA-1=C-1的矩阵P为() A、 B、 C、 D．

【单选题】： A     B     C     D

第2题：分子结构中含有两个羧基的氨基酸是 A．丝氨酸 B．谷氨酸 C．酪氨酸 D．苏氨酸

【单选题】： A     B     C     D

Addiction is such a harmful behavior, in fact, that evolution should have long ago weeded it out of the population: if it’s hard to drive safely under the influence, imagine trying to run from a saber-toothed tiger or catch a squirrel for lunch.And yet, saysDr. Nora Volkow, director of NIDA、and a pioneer in the use of imaging to understand addiction, "the use of drugs has been recorded since the beginning of civilization. Humans in my view will always want to experiment with things to make them feel gooD、"
That’s because drugs of abuse co-opt the very brain functions that allowed our distant ancestors to survive in a hostile worlD、Our minds are programmed to pay extra attention to what neurologists call salience—that is, special relevance. Threats, for example, are highly salient, which is why we instinctively try to get away from them.But so are food and sex because they help the individual and the species survive.Drugs of abuse capitalize on this ready-made programming. When exposed to drugs, our memory systems, reward circuits, decision making skills and conditioning kick in—salience in overdrive—to create an all consuming pattern of uncontrollable craving. "Some people have a genetic predisposition to addiction," says Volkow. "But because it involves these basic brain functions, everyone will become an addict if sufficiently exposed to drugs or alcohol."
That can go for nonchemical addictions as well.Behaviors, from gambling to shopping to sex, may start out as habits but slide into addictions. Sometimes there might be a behavior-specific root of the problem. Volkow’s research group, for example, has shown that pathologically obese people who are compulsive eaters exhibit hyperactivity in the areas of the brain that process food stimuli—including the mouth, lips and tongue. For them, activating these regions is like opening the floodgates to the pleasure center.Almost anything deeply enjoyable can turn into an addiction, though.
Of course, not everyone becomes an addict. That’s because we have other, more analytical regions that can evaluate consequences and override mere pleasure seeking.Brain imaging is showing exactly how that happens. Paulus, for example, looked at drug addicts enrolled in a VA、hospital’s intensive four-week rehabilitation program. Those who were more likely to relapse in the first year after completing the program were also less able to complete tasks involving cognitive skills and less able to adjust to new rules quickly. This suggested that those patients might also be less adept at using analytical areas of the brain while performing decision-making tasks. Sure enough, brain scans showed that there were reduced levels of activation in the prefrontal cortex, where rational thought can override impulsive behavior. It’s impossible to say if the drugs might have damaged these abilities in the relapsers an effect rather than a cause of the chemical abuse—but the fact that the cognitive deficit existed in only some of the drug users suggests that there was something innate that was unique to them. To his surprise, Paulus found that 80% to 90% of the time, he could accurately predict: who would relapse within a year simply by examining the scans.
Another area of focus for researchers involves the brain’s reward system, powered largely by the neurotransmitter dopamine. Investigators are looking specifically at the family of dopamine receptors that populate nerve cells and bind to the compounD、The hope is that if you can reduce the effect of the brain chemical that carries the pleasurable signal, you can loosen the

第3题： {{B}}PartA{{/B}} {{B}}Directions:{{/B}} Read the following four texts.Answer the questions below each text by choosingA,B,C、orD、Mark your answers onANSWER SHEET 1. {{B}}Text 1{{/B}}

【单选题】： A     B     C     D

第4题：“呕而肠鸣，心下痞者”宜用 A．半夏泻心汤 B．生姜泻心汤 C．甘草泻心汤 D．黄连汤

【单选题】： A     B     C     D

第5题：术前常规禁食的主要目的是 A．避免胃膨胀而妨碍手术 B．防止围手术期的呕吐及误吸 C．防止术后腹胀 D．防止术后肠麻痹

【单选题】： A     B     C     D