Question

    Cells in our brain usually send “stop eating” signal when we’ve had enough. But after mice ate fatty foods for just two weeks, their brains’ brake on overeating quieted down. That finding may help explain the complex link between food and appetite that can become disordered when people overeat.

Food is essential to life. Our brains have, therefore, evolved a series of systems to make sure we eat enough. Garret Stuber, a neuroscientist at the University of Washington, together with his team 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 group looked at the behaviors of genes in the cells here. And in one type—glutamatergic nerve (谷氨酸能神经) cells—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. When the 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 overnight,” notes Stuber. To find out the secret, his group undertook a new study. They fed mice high-fat food. Now and again, they’d use a fancy microscope 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 these nerve cells had slowed. It continued as the animals grew larger over a 12-week period. “The cells’ activity was going down as a function of high-fat diet. The results suggest that the high-fat diet 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 tests have shown that the same brain region —the hypothalamus—plays a role when people shift between 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 fullness.

2.It can be learned from the text that glutamatergic nerve cells ________.

A.are easily found in lean mice B.can prevent mice from overeating

C.function well under any condition D.are a main part of lateral hypothalamus

3.Why did Stuber’s group undertake the new study?

A.To study the role of glutamatergic cells in mice’s fattening up.

B.To find out the link between high-fat diets and obesity.

C.To find out deciding factors in mice’s appetite.

D.To study the eating habit of fat mice.

4.What is the main idea of the text?

A.Obesity influences glutamatergic nerves’ function.

B.Glutamatergic nerves decide people’s appetite.

C.High-fat diets lead to overeating.

D.Our brains control our food choices.

Answer

1.D

2.B

3.A

4.C

【解析】

这是一篇说明文。文章主要说明了研究人员通过试验发现，老鼠只吃了两周的高脂肪食物，他们的大脑对过量饮食的抑制就会平静下来。这一发现可能有助于解释食物和食欲之间的复杂联系，当人们吃得过多时，食欲会变得紊乱。研究人员发现侧下丘脑中一种名为谷氨酸能神经的细胞可以防止暴饮暴食，就像是进食的刹车，而高脂肪饮食会让这类细胞的活动减缓。

1.

细节理解题。根据第一段中But after mice ate fatty foods for just two weeks, their brains’ brake on overeating quieted down.可知但是，老鼠只吃了两周的高脂肪食物，他们的大脑对过量饮食的抑制就会平静下来。由此可知，老鼠吃了两周高脂肪食物后，发生了缺乏饱腹感的情况。故选D。

2.

细节理解题。根据第三段中And in one type—glutamatergic nerve (谷氨酸能神经) cells—big differences appear between fat mice and lean ones.可知在一种类型的谷氨酸神经细胞中，肥壮老鼠和瘦老鼠之间出现了巨大的差异。以及第四段中Earlier work by Stuber’s group had suggested that these cells act like a brake on eating. When the researchers prevented these cells from firing, mice suddenly overate.可知斯图博团队早期的研究表明，这些细胞起到了抑制进食的作用。 当研究人员阻止这些细胞活动时，老鼠突然暴饮暴食。由此可知，谷氨酸神经细胞可以防止老鼠暴饮暴食。故选B。

3.

推理判断题。根据第五段“Obesity doesn’t just happen overnight,” notes Stuber. To find out the secret, his group undertook a new study. They fed mice high-fat food. Now and again, they’d use a fancy microscope to look at how well the animals’ glutamatergic cells could fire off signals.可知“肥胖不是一夜之间就会发生的，” Stuber指出。为了找出这个秘密，他的小组进行了一项新的研究。他们给老鼠喂高脂肪食物。时不时地，他们会用一台奇特的显微镜来观察动物的谷氨酸细胞发出信号的能力。由此可推知，Stuber的小组进行这项新的研究，是为了研究谷氨酸细胞在老鼠增肥中的作用。故选A。

4.

主旨大意题。根据第一段中But after mice ate fatty foods for just two weeks, their brains’ brake on overeating quieted down. That finding may help explain the complex link between food and appetite that can become disordered when people overeat.可知但是，老鼠只吃了两周的高脂肪食物，他们的大脑对过量饮食的抑制就会平静下来。这一发现可能有助于解释食物和食欲之间的复杂联系，当人们吃得过多时，食欲会变得紊乱。结合文章还说明了研究人员发现侧下丘脑中一种名为谷氨酸能神经的细胞可以防止暴饮暴食，就像是进食的刹车，而高脂肪饮食会让这类细胞的活动减缓。由此可知，这篇文章的主旨是高脂肪饮食导致暴饮暴食。故选C。