首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
It was once believed that the brain was independent of metabolic processes occurring elsewhere in the body. In recent studies, h
It was once believed that the brain was independent of metabolic processes occurring elsewhere in the body. In recent studies, h
admin
2019-02-01
41
问题
It was once believed that the brain was independent of metabolic processes occurring elsewhere in the body. In recent studies, however, we have discov- ered that the production and release in brain neurons of the neurotransmitter serotonin(neurotransmitters are compounds that neurons use to transmit signals to other cells)depend directly on the food that the body processes.
Our first studies sought to determine whether the increase in serotonin observed in rats given a large injection of the amino acid tryptophan might also occur after rats ate meals that change tryptophan levels in the blood. We found that, immediately after the rats began to eat, parallel elevations occurred in blood tryptophan, brain tryptophan, and brain serotonin levels. These findings suggested that the production and release of serotonin in brain neurons were normally coupled with blood-tryp-tophan increases. In later studies we found that injecting insulin into a rat’s bloodstream also caused parallel elevations in blood and brain tryptophan levels and in serotonin levels. We then decided to see whether the secretion of the animal’s own insulin similarly affected serotonin production. We gave the rats a carbohydrate-containing meal that we knew would elicit insulin secretion. As we had hypothesized, the blood trypto- phan level and the concentrations of tryptophan serotonin in the brain increased after the meal.
Surprisingly, however, when we added a large amount of protein to the meal, brain tryptophan and serotonin levels fell. Since protein contains tryptophan, why should it depress brain tryptophan levels? The answer lies in the mechanism that provides blood tryp- tophan to the brain cells. This same mechanism also provides the brain cells with other amino acids found in protein, such as tyrosine and leucine. The consumption of protein increases blood con- centration of the other amino acids much more, proportionately, than it does that of tryptophan. The more protein in the meal, the lower is the ratio of the resulting blood-tryptophan concentration to the concentration of competing amino acids, and the more slowly is tryptophan provided to the brain. Thus the more protein in a meal, the less serotonin subsequently produced and re- leased.
It can be inferred from the passage that which of the following would be LEAST likely to be a potential source of aid to a patient who was not adequately producing and releasing serotonin?
选项
A、Meals consisting almost exclusively of protein.
B、Meals consisting almost exclusively of carbohydrates.
C、Meals that would elicit insulin secretion.
D、Meals that had very low concentrations of tyrosine.
E、Meals that had very low concentrations of leucine.
答案
A
解析
哪一个是最不可能的一种帮助——不能以有效的方式分泌病人的血清素?A.只含蛋白质的食物。正确。蛋白质含量越高,血清素分泌得越少。文章末句结论(L57—60)。注意:exclusively=only。B.只有碳水化合物。讲反了,若这样,有利于胰岛素及血清素分泌。C.促进胰岛素分泌。这也会促进血清素分泌。D中的tyrosine和E中的leucine本身的含量和血清素没有联系。
转载请注明原文地址:https://kaotiyun.com/show/GmkO777K
本试题收录于:
GMAT VERBAL题库GMAT分类
0
GMAT VERBAL
GMAT
相关试题推荐
Evenachildknowsthatnoddingheadmeans"Yes".Butsomepeoplewouldprobably【C1】______whentheyfirstcametoIndia.Whent
Asanymiddle-classparentknows,unpaidworkexperiencecangiveyoungstersavaluableintroductiontoasecurejob.Thegovern
TheUnitedStates【C1】______alargepartoftheNorthAmericancontinent.ItsneighborsareCanada【C2】______thenorth,andMexico
TheUnitedStates【C1】______alargepartoftheNorthAmericancontinent.ItsneighborsareCanada【C2】______thenorth,andMexico
"Helicopterparenting"describesastyleofraisingchildrenwhereparentsareover-protectiveanddotoomuch.Thetermwasuse
Atransplantoperationissuccessfulonlyifdoctorscanpreventthebodyfromrejectingthe______organ.
Overtheyears,collegestudentshavestoodtogetherforwhattheybelievein,fromcivilrightstoanti-warpoliciestothemor
Spending50minuteswithacellphoneclosetoyourearisenoughtochangebraincellactivityinthepartofthebrainclosest
Economicdevelopmentdependsontheextractionofnaturalresourcesandonlow-skilledlabor,whichhasresultedinaweakmanuf
"I’mnot100%convincedthatmemorizingthedictionaryisthebestwayofimprovingyourvocabulary."saysthecharacterplayed
随机试题
以下关于假设检验的命题,哪项是正确的?()
A.原发性腹膜炎B.盆腔脓肿C.继发性腹膜炎D.出血性腹膜炎E.慢性腹膜炎直肠前壁扪及触痛性肿块
老年性阴道炎进行阴道灌洗常用的药液是
不同评价级别项目生态影响预测内容要求有所不同,如评价级别为2级项目,则()。
建设工程监理具有服务性,主要是从()定性的。
业主直接控制所有工程的发包,可决定所有工程的承包商的选择,属于施工平行承发包模式中的()的内容。
乙股份有限公司当期发生的下列交易或事项中,其现金流量变动属于筹资活动产生的现金流量的有()。
“虚拟物流”的英文是()。
我国第一部以偏旁部首整理出来的字书是()。
Theunknownpervadestheuniverse.Thatwhichpeoplecansee,withtheaidofvarioussortsoftelescope,accountsforjust4%o
最新回复
(
0
)