学生啦：课时作业（二）Unit1 SectionⅡGrammar and usage IntegratedskillsACells in our brain usually send "stop eating"signal when we've had enough.But after miceate fatty foods for just two weeks,their brains'brake on overeating quieted down.That findingmay help explain the complex link between food and appetite that can become disordered whenpeople overeat.Food is essential to life.Our brains have,therefore,evolved a series of systems to make surewe eat enough.Garret Stuber,a neuroscientist at the University of Washington,together with histeam took aim at one brain area known to be involved in eating behaviors.This lateral hypothalamus(下丘脑外侧区)contains many diverse cells.Stuber's grouplooked at the behaviors of genes in the cells here..And in one type-一glutamatergic nerve(谷氦酸能神经)cells-一big differences appear between fat mice and lean ones..Earlier work by Stuber's group had suggested that these cells act like a brake on eating.Whenthe researchers prevented these cells from firing,mice suddenly overate.They also fattened up.But it wasn't clear how the cells'activity changed as the mice transitioned from slim to fat."Obesity doesn't just happen ovemight,notes Stuber.To find out the secret,his groupundertook a new study.They fed mice high-fat food.Now and again,they'd use a fancymicroscope to look at how well the animals'glutamatergic cells could fire off signals.Two weeks into the high-fat food-even before the mice became round-the activity of thesenerve cells had slowed.It continued as the animals grew larger over a 12-week period."Thecells'activity was going down as a function of high-fat diet.The results suggest that the high-fatdiet is removing the brake on eating and obesity,explains Stuber.It's hard to say whether similar cells normally control people's appetite.Brain-imaging testshave shown that the same brain region -the hypothalamus-plays a role when people shiftbetween hunger and feeling full.1.What happened after the mice ate fatty foods for two weeks?A.Their appetite was getting worse.B.Their brains became disordered.C.They refused to eat zero fat food.D.They lacked a feeling of fullness2.It can be learned from the text that glutamatergic nerve cellsA.are easily found in lean miceB.can prevent mice from overeatingD.are a main part of lateral hypothalamus3.Why did Stuber's group undertake the new study?A.To study the role of glutamatergic cells in mice's fattening up.