首页
登录
职称英语
Nose has it pretty hard, Boxers flatten them. Doctors rearrange them. People
Nose has it pretty hard, Boxers flatten them. Doctors rearrange them. People
游客
2025-03-27
15
管理
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. [br] 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://tihaiku.com/zcyy/4015347.html
相关试题推荐
Ioftenwonderwhysomepeoplewon’tdowhatit______tobesuccessful.A、involv
Inthisageofthekeyboard,somepeopleseemtothinkhandwritinglessonsare_
Inthisageofthekeyboard,somepeopleseemtothinkhandwritinglessonsare_
Itisestimatedthatatleastonemillionpeopledieeveryyearbecauseofcompl
Itisestimatedthatatleastonemillionpeopledieeveryyearbecauseofcompl
Itisestimatedthatatleastonemillionpeopledieeveryyearbecauseofcompl
Studieshaveprovedthatsmartpeopletendtobesmartacrossdifferentkindsof
Someancientpeoplewereabletotellthetimebytheshadow______bythesunon
SomepeopleareskepticalaboutthevalidityofAristotle’sargumentthatmanis
Asthetrainservicehadbeensuspended,thousandsofpeoplehadtowaitforday
随机试题
[audioFiles]audio_eusm_j56_001(20082)[/audioFiles]A、Theyareveryappealingwit
土方作业阶段达到作业区目测扬尘高度小于()。A.1.0m B.1.2m C
1996年3月,IEEE成立了802.3z工作组开始制定1000M
患者,女,40岁,因关节肿痛伴僵硬多年,诊断为类风湿关节炎。其发病的相关因素是(
在红外辐射技术的研究和应用中,设定了具有理想中最大辐射功率的物体,称之为黑体,黑
教学“除数是小数的除法”,某教师把分12个馒头的计算板书出来:12÷3=4(人)
直接决定某一房地产价格水平高低的供求状况,主要是()房地产的供求状况。A.
投资者通过基金管理人及其他代销机构在深圳证券交易所认购上市开放式基金,应使用中国
根据年龄层可以把生涯规划比照家庭生命周期分为6个阶段,理财活动侧重于偿还房贷、筹
应在施工期间及使用期间进行变形观测的建筑物有()。A.地基基础设计等级为
最新回复
(
0
)