[外语类试卷]大学英语六级模拟试卷847(无答案).doc
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1、大学英语六级模拟试卷 847(无答案)一、Part I Writing (30 minutes)1 For this part, you are allowed 30 minutes to write a short essay entitled Post-holiday Syndrome Among Students. You should write at least 150 words following the outline given below.1很多学生在开学伊始都会出现假期综合症2出现这一现象的原因3我的建议Post-holiday Syndrome Among Studen
2、ts二、Part II Reading Comprehension (Skimming and Scanning) (15 minutes)Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-4, mark:Y (for YES) if the statement agrees with the information given in the pass
3、age;N (for NO) if the statement contradicts the information given in the passage;NG (for NOT GIVEN) if the information is not given in the passage.1 How “Second Brain“ Influences Mood and Weil-BeingAs Olympians go for the gold in Vancouver, even the steeliest are likely to experience that familiar f
4、eeling of “butterflies“ in the stomach. Underlying this sensation is an often-overlooked network of neurons(神经元)lining our guts that is so extensive some scientists have nicknamed it our “second brain“.A deeper understanding of this mass of neural tissue is revealing that it does much more than mere
5、ly handle digestion or inflict the occasional nervous pang. The little brain in our gut, in connection with the big one in our head, partly determines our mental state and plays key roles in certain diseases throughout the body.Although its influence is far-reaching, the second brain is not the seat
6、 of any conscious thoughts or decision-making.“The second brain doesnt help with the great thought processes. religion, philosophy and poetry is left to the brain in the head,“ says Michael Gershon, chairman of the Department of Anatomy and Cell Biology at New York-Presbyterian Hospital/Columbia Uni
7、versity Medical Center, author of the 1998 book The Second Brain.Technically known as the enteric(肠内的)nervous system, the second brain consists of covers of neurons embedded in the walls of the long tube of our gut, which measures about nine meters end to end. The second brain contains some 100 mill
8、ion neurons, Gershon says.This multitude of neurons in the enteric nervous system enables us to “feel“ the inner world of our gut and its contents. Much of this neural firepower comes to bear in the elaborate daily grind of digestion. Breaking down food, absorbing nutrients, and expelling of waste r
9、equires chemical processing, mechanical mixing and rhythmic muscle contractions that move everything on down the line.Thus equipped with its own reactions and senses, the second brain can control gut behavior independently of the brain, Gershon says. We likely evolved this intricate web of nerves to
10、 perform digestion and ejection “ on site,“ rather than remotely from our brains through the middleman of the spinal cord(脊髓 ). “The brain in the head doesnt need to get its hands dirty with the messy business of digestion, which is delegated to the brain in the gut,“ Gershon says. He and other rese
11、archers explain, however, that the second brains complexity likely cannot be interpreted through this process alone.“ The system is way too complicated to have evolved only to make sure things move out of your bowel,“ says Emeran Mayer, professor of physiology, psychiatry and biobehavioral sciences
12、at the David Geffen School of Medicine at the University of California, Los Angeles(U. C. L. A.). For example, scientists were shocked to learn that about 90 percent of the fibers in the primary gut nerve, the vagus(迷走神经), carry information from the gut to the brain and not the other way around. “ S
13、ome of that information is decidedly unpleasant,“ Gershon says.The second brain informs our state of mind in other more obscure ways, as well. “ A big part of our emotions are probably influenced by the nerves in our gut,“ Mayer says. Butterflies in the stomach signaling in the gut as part of our ph
14、ysiological stress response, Gershon saysis but one example. Although gastrointestinal(肠胃)(GI)chaos can sour ones moods, everyday emotional well-being may rely on messages from the brain below to the brain above. For example, electrical stimulation of the vagus nervea useful treatment for depression
15、may mimic these signals, Gershon says.Given the two brains commonalities, other depression treatments that target the mind can unintentionally impact the gut. The enteric nervous system uses more than 30 neurotransmitters, just like the brain, and in fact 95 percent of the bodys serotonin(血清素)is fou
16、nd in the bowels. Because antidepressant medications called selective serotonin reuptake inhibitors(选择性五羟色胺再摄取抑制剂)(SSRIs)increase serotonin levels, its little wonder that meds(椎间盘镜)meant to cause chemical changes in the mind often provoke GI issues as a side effect. Irritable bowel syndromewhich aff
17、licts more than two million Americansalso arises in part from too much serotonin in our guts, and could perhaps be regarded as a “mental illness“ of the second brain.Scientists are learning that the serotonin made by the enteric nervous system might also play a role in more surprising diseases: In a
18、 new Nature Medicine study published online February 7, a drug that inhibited the release of serotonin from the gut counteracted the bone-deteriorating disease osteoporosis(骨质疏松症). “It was totally unexpected that the gut would regulate bone mass to the extent that one could use this regulation to cu
19、re osteoporosis,“ says Gerard Karsenty, lead author of the study and chair of the Department of Genetics and Development at Columbia University Medical Center.Serotonin penetrating from the second brain might even play some part in autism(孤独症), the developmental disorder often first noticed in early
20、 childhood. Gershon has discovered that the same genes involved in synapse formation(突触形成)between neurons in the brain are involved in the digestive synapse formation. “ If these genes are affected in autism,“ he says, “ it could explain why so many kids with autism have GI motor abnormalities in ad
21、dition to elevated levels of gut-produced serotonin in their blood. “Down the road, the blossoming field of neurogastroenterology will likely offer some new insight into the workings of the second brainand its impact on the body and mind. “ We have never systematically looked at the enteric nervous
22、system in relating damages in it to diseases like they have for the central nervous system“ , Gershon says. One day, perhaps there will be well-known connections between diseases and damages in the guts nervous system as some in the brain and spinal cord today indicate multiple sclerosis(硬化症).Cuttin
23、g-edge research is currently investigating how the second brain mediates the bodys immune response; after all, at least 70 percent of our immune system is aimed at the gut to expel and kill foreign invaders.U. C. L. A. s Mayer is doing work on how the trillions of bacteria in the gut “communicate“ w
24、ith enteric nervous system cells(which they greatly outnumber). His work with the enteric nervous system has led him to think that in coining years psychiatry will need to expand to treat the second brain in addition to the one above the shoulders.So for those physically skilled and mentally strong
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