考研英语核心词汇速成胜经Unit 12
一、 真题文章
The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, while this is largely because, unlike animals ,we stand upright. This means that our noses are limited to perceiving those smells which float through the air, missing the majority of smells which stick to surfaces. In fact, instead , we are extremely sensitive to smells, even if we do not generally realize it. Our noses are capable of detecting human smells even when these are diluted to far below one part in one million.
Strangely, some people find that they can smell one type of flower but not another, whereas others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate particular smell receptors in the nose. These receptors are the cells which sense smells and send messages to the brain. However, it has been found that even people insensitive to a certain smell at first can suddenly become sensitive to it when exposed to it often enough.
The explanation for insensitivity to smell seems to be that brain finds it inefficient to keep all smell receptors working all the time but can trigger new receptors if necessary. This may also explain why we are not usually sensitive to our own smells ----we simply do not need to be. We are not aware of the usual smell of our own house but we notice new smells when we visit someone else's. The brain finds it best to keep smell receptors available for unfamiliar and emergency signals such as the smell of smoke, which might indicate the danger of fire.
二、 译文
人类的鼻子是一个被低估的工具。人们通常认为，与动物相比，人类的嗅觉不灵敏，但是这在很大程度上是因为人类与动物不同，我们是直立的。这就意味着，我们的鼻子仅限于嗅出那些通过空气飘散的气味，而错失绝大多数依附于地表的气味。但是，实际上，我们对气味是相当敏感的，即使我们通常没有意识到这一点。当人类的气味被淡化到远低于一百万分之一时，我们的鼻子也能侦测到这些气味。
奇怪的是，有些人认为他们可以闻出一种花香，却闻不出另一种，而有些人却对两种花香都很敏感。这可能是因为有些人缺少某种基因，这种基因正好用于产生鼻子里对某种味道的感受器。这些感受器是由一些能感知气味并把信息传递给大脑的细胞构成的。然而，研究发现即使人们最开始对某种气味不敏感，但当人们能经常大量地闻到这种气味后也能突然对它很敏感。
对气味不敏感的解释似乎是这样的：大脑觉得无法让所有气味接受器始终有效地运作，但是，如果有需要的话，大脑可以创造新的接受器。这也可能说明了我们为什么对自己的气味不敏感的原因——我们不需要这样。我们不知道我们自己家里的平常气味，但是，当我们拜访其他人的家时，我们注意到新的气味。大脑觉得，最好让所有接受器可得到不熟悉和紧急信号，例如烟雾的气味，它可能预示有火灾的危险。
三、 考研核心词汇
underrate / 7QndE5reit / vt. 低估, 看轻
责任编辑:zhaotingting
