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
Nose has it pretty hard, Boxers flatten them. Doctors rearrange them. People make jokes about their unflattering characteristics
Nose has it pretty hard, Boxers flatten them. Doctors rearrange them. People make jokes about their unflattering characteristics
admin
2013-01-10
120
问题
Nose has it pretty hard, Boxers flatten them. Doctors rearrange them. People make jokes about their unflattering characteristics. Worst of all, when it comes to smell, no one really understands them.
Despite the nose’s conspicuous presence, its workings are subtle. Smell, or olfaction, is a chemo-sense, relying on specialized interactions between chemicals and nerve endings. When a rose, for example, is sniffed, odor molecules are carried by the rising air-stream to the top of the nasal cavity, just behind the bridge of the nose, where the tips of the tends of millions of olfactory nerve cells are clustered in the mucous lining. The molecules somehow trigger the nerve ending, white carry the message to the olfactory lobes of the brain. Because smell information then travels to other region of the brain, the scent of a rose can elicit not only a pleasure sensation but emotions and memories as well.
Though just how odors stimulate the nerves is unknown, scientists do know that our sense of smell is surprisingly keen capable of distinguishing up to tens of thousands of chemical odors. The laboratory task of isolating the components must of an odor is far from simple .Tobacco smoke, for example, is made up of several thousand different chemicals. Moreover smell by their sources or associations. Description such as "like a wet dog" or "like my elementary school" may convey perceptions but are vastly inadequate for labeling the chemistry involved.
To further complicate research, olfaction is connected to other sensations. Besides olfactory nerves, the nasal cavity contains pain-sensitive nerves that perceive sensations such as the kick in ammonia or the burning in chili peppers. Smell also inter-wines with taste to create flavor. A coffee drinker holding his nose while sipping would taste only the bitter in his brew, for taste receptors generally appear limited to bitter, salty, sour, and sweet. The sense of smell is ten thousand times more sensitive than taste and makes subtle distinctions among lemon, chocolate, and many more flavors.
So how does the nose manage this sophisticated discrimination? Lack of evidence hasn’t kept scientists from speculating. One idea is that every odor molecule vibrates at its own frequency, creating patterns of disturbance in the air similar to the wave patterns produced by sound. According to this theory, the nerves act as receives for the unique vibrations of every odor molecule. The scheme requires no direct contact between the molecule and the nerve cell.
Another suggestion is that primary odors, equivalent to the primary colors of vision, underlie all smells and are detected by receptor sites on the olfactory nerves. Different combinations of about thirty basic smells, with labels such as malty, minty, and musky, could form an infinite number of odors.
Other scientists think that each smell is its own primary smell. They believe the olfactory nerve endings have specific receptor proteins that bind to each of the chemicals people can sense. This theory, however, calls for thousands of different proteins-none of which has been found.
"The science of smell is so empirical," says Robert Gesteland, a neurobiologist at Northwestern University, "there is no predictive base for experiments." Unlike the senses of sight, touch, and hearing, olfaction studies have attracted only a small share of scientific interest. That may change. Researchers hope that unraveling the mystery of smell will advance our understanding of the future, with enough known about smell, it might be possible to endow strange, unappealing but nutritious foods with more familiar odors, perhaps expanding the world’s food supply. For the moment, however, what the nose knows it isn’t revealing.
We may conclude from this passage that______.
选项
A、our sense of smell is as important as any of our other senses
B、each smell is its own primary smell
C、olfactory study has become a major research area
D、there is much more to be learned about the nose
答案
D
解析
纵观全文,作者始终围绕了解nose的问题进行讨论,文中最后一段也指出,研究nose应建立在观察和经验的基础之上,而不是建立在实验的基础之上。故D项为正确答案。
转载请注明原文地址:https://kaotiyun.com/show/pZTO777K
0
研究生英语学位课统考(GET)
相关试题推荐
Thecomingofautomationis______tohaveimportantsocialconsequences.(2002年春季上海交通大学考博试题)
Sheistryingto______himbyphoneasshehassomeveryimportantnewsforhim.(2011年南京大学考博试题)
MostpeoplewhodevelopedLymedisease,atick-borninfectionthat’sendemicinpartsoftheNortheastandMidwest,areeasilyc
Planningisaveryimportantactivityinourlivesyetreallysophisticated.Itcangivepleasure,evenexcitement,【C1】______ca
Planningisaveryimportantactivityinourlivesyetreallysophisticated.Itcangivepleasure,evenexcitement,【C1】______ca
ThatTVnewsprogramplays______sensationalstoriesjusttogethigherratings.
Anupsurgeofnewresearchsuggestsanimalshaveamuchhigherlevelofbrainpowerthanpreviousthought.Beforedefininganimal
Germany,Europe’seconomicpowerhouse,doesnotlackcourage:itreboundedfromtwoworldwars,digestedreunificationandhasn
随机试题
菜肴质的搭配,是指菜肴中主料、辅料质地的搭配。()
半挡板一般需要半价层的个数为
下列哪种情况常有震颤
某面粉加工车间消防员王某对车间内重点区域电气设施的安装情况定期检查、维护、管理。建筑内部装修中,关于照明灯具和配电箱的安装的检查,下列说法正确的是()
所有者权益金额取决于资产、负债和利润的计算。()
运用本量利分析法进行利润预测的基本方法有()。
一、注意事项1.申论考试,与传统作文考试不同,是对分析驾驭材料的能力与对表达能力并重的考试。2.作答参考时限:阅读资料40分钟,作答110分钟。3.仔细阅读给定的资料,按照后面提出的“申论要求”依次作答。二、资料1.200
为亚述帝国奠定版图基础的是公元前9世纪前期的亚述王()。
诸侯国的国君如何用人呢?有人主张:“左右皆日不可,勿听;诸大夫皆日不可,勿听;国人皆日不可,然后察之,见不可焉,然后去之。”这种主张最终可能出自下列哪位思想家之口()。
托马斯和切斯等人研究婴儿气质类型时首先确定了气质的维度,他们确定的气质维度的数量是
最新回复
(
0
)