托福听力短文 II-10-1

(WA) Did you ever wonder why it is that most people are "programmed" to sleep at night instead of during the day? If there's something about the cycle of light and dark that's telling us when to sleep, then shouldn't the sleep cycle of a blind person be different? As it turns out, many blind people --- people with no visual perception¹ of light at all --- do have the same sleep cycle as sighted people.

So now you're wondering, "How can this happen?" The answer is: hormones³ --- one hormone² in particular. It's called melatonin. In sighted people, the level of melatonin goes up at night (or when it's dark) and goes down in the day (or when it's light). It's believed that it's the presence of this hormone in the blood that gives us the urge to sleep. If an increase in melatonin level "programs" sighted people to sleep at night, then what about blind people?

A researcher named Dr. Charles Czeisler, tells about an interesting experiment. He tried shining a bright light into the eyes of some blind people. When he did this, he noticed that the level of the melatonin in the blood of these subjects went down --- just as it would do for sighted people. Somehow, the eyes of these subjects, even though they were damaged and had no visual perception of light, could tell their brain when there was more or less light. Now, this doesn't work for all blind people; in fact, most of Czeisler's subjects had no hormonal⁴ response to light at all. Further research may be able to explain this sensitivity⁵ to light in terms of the type of blindness of the subject.

1 perception   

n.感知，感觉，觉察(力)；认识，观念，看法

参考例句：

• What's your perception of the matter?你对此事有什么看法？
• He was a man of keen perception.他是一个感觉敏锐的人。

2 hormone   

n.荷尔蒙，激素，内分泌

参考例句：

• Hormone implants are used as growth boosters.激素植入物被用作生长辅助剂。
• This hormone interacts closely with other hormones in the body.这种荷尔蒙与体內其他荷尔蒙紧密地相互作用。

3 hormones   

n. 荷尔蒙，激素 名词hormone的复数形式

参考例句：

• This hormone interacts closely with other hormones in the body. 这种荷尔蒙与体內其他荷尔蒙紧密地相互作用。
• The adrenals produce a large per cent of a man's sex hormones. 肾上腺分泌人体的大部分性激素。

4 hormonal   

adj.激素的

参考例句：

• Some viral diseases are more severe during pregnancy, probably tecause of hormonal changes. 有些病毒病在妊娠期间比较严重，可能是由于激素变化引起的。
• She underwent surgical intervention and a subsequent short period of hormonal therapy. 他接受外科手术及随后短暂荷尔蒙治疗。

5 sensitivity   

n.敏感（性），灵敏（度）

参考例句：

• Hearing sensitivity declines with age.听觉因年老而衰退。
• Such is the sensitivity of the information that only two people are allowed to know it.这信息极为敏感，只允许两个人知道。