生活百态:为什么我们的身体会发麻？

 保持一个姿势久了，身体就会有发麻的感觉。当你改变姿势的时候，会感到非常的难受：刺痛、痉挛，然后是慢慢恢复知觉。这种发麻的滋味还真不好受。那么，为什么我们的身体会发麻呢？看了下面这篇文章你就会有所了解了。

The unnerving, separate sensations we feel when a body part "falls asleep" truly result from nerves under pressure.

Scientists, using the arm as an example of a limb that has fallen asleep, explain that the person, most likely, slept on the arm. This sleeping position exerted pressure on the nerves, which squeezed them and, thus, inhibited¹ the messages the nerves carry to the brain and to the rest of the body. If sleeping on the arm also squeezed the blood vessels², oxygen normally carried to the nerves by these vessels never made it to its destination.

The nerves themselves comprise bundles of single celled fibers⁴, with each fiber³ conveying a different sensation or message to the brain. The fibers vary in thickness and in the amounts of myelin, a protective sheath, surrounding them. These two variables determine the sensitivity of the nerve fiber to pressure and to oxygen deprivation⁵. As a general rule, the thicker the fiber, and the larger the myelin sheath, the more sensitive it is.

When one removes the pressure on the nerves and on the blood vessels, in this case by a change in sleeping position, the nerve fibers awaken⁶ in order of their thickness and of the thickness of their myelin sheaths. Hence, the thickest and most protected ones awaken last. This gradual awakening⁷ process causes the different sensations we experience as the affected⁸ body part returns to its functional⁹ state.

The first sensation we experience is a tingling¹⁰ sensation, followed by a burning sensation, as the fibers that control pain and temperature now function and are again able to transmit these messages to the brain. Not until later, does the numbness¹¹ we feel disappear, simply because the fibers that control touch and position are thicker fibers with thicker myelin sheaths. Similar fibers, known as motor neurons, travel in the same nerves, but take direct orders from the brain to the spinal¹² cord to the muscles, and awaken shortly after those controlling touch and position. For this reason, after the numbness disappears, we regain¹³ our ability to move the affected body part, and life is finally backed to normal.

unnerving: 身心疲惫

myelin: 髓磷脂

tingling: 刺痛

1 inhibited   

a.拘谨的，拘束的

参考例句：

• Boys are often more inhibited than girls about discussing their problems. 男孩子往往不如女孩子敢于谈论自己的问题。
• Having been laughed at for his lameness,the boy became shy and inhibited. 那男孩因跛脚被人讥笑，变得羞怯而压抑。

2 vessels   

n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人

参考例句：

• The river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。 来自《简明英汉词典》
• All modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。 来自《现代汉英综合大词典》

3 fiber   

n.纤维，纤维质

参考例句：

• The basic structural unit of yarn is the fiber.纤维是纱的基本结构单元。
• The material must be free of fiber clumps.这种材料必须无纤维块。

4 fibers   

光纤( fiber的名词复数 )； （织物的）质地； 纤维，纤维物质

参考例句：

• Thesolution of collagen-PVA was wet spined with the sodium sulfate as coagulant and collagen-PVA composite fibers were prepared. 在此基础上，以硫酸钠为凝固剂，对胶原-PVA共混溶液进行湿法纺丝，制备了胶原-PVA复合纤维。
• Sympathetic fibers are distributed to all regions of the heart. 交感神经纤维分布于心脏的所有部分。

5 deprivation   

n.匮乏；丧失；夺去，贫困

参考例句：

• Many studies make it clear that sleep deprivation is dangerous.多实验都证实了睡眠被剥夺是危险的。
• Missing the holiday was a great deprivation.错过假日是极大的损失。

6 awaken   

vi.醒，觉醒；vt.唤醒，使觉醒，唤起，激起

参考例句：

• Old people awaken early in the morning.老年人早晨醒得早。
• Please awaken me at six.请于六点叫醒我。

7 awakening   

n.觉醒，醒悟 adj.觉醒中的；唤醒的

参考例句：

• the awakening of interest in the environment 对环境产生的兴趣
• People are gradually awakening to their rights. 人们正逐渐意识到自己的权利。

8 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

9 functional   

adj.为实用而设计的，具备功能的，起作用的

参考例句：

• The telephone was out of order,but is functional now.电话刚才坏了，但现在可以用了。
• The furniture is not fancy,just functional.这些家具不是摆着好看的，只是为了实用。

10 tingling   

v.有刺痛感( tingle的现在分词 )

参考例句：

• My ears are tingling [humming; ringing; singing]. 我耳鸣。 来自《现代汉英综合大词典》
• My tongue is tingling. 舌头发麻。 来自《现代汉英综合大词典》

11 numbness   

n.无感觉，麻木，惊呆

参考例句：

• She was fighting off the numbness of frostbite. 她在竭力摆脱冻僵的感觉。 来自《简明英汉词典》
• Sometimes they stay dead, causing' only numbness. 有时，它们没有任何反应，只会造成麻木。 来自时文部分

12 spinal   

adj.针的，尖刺的，尖刺状突起的；adj.脊骨的，脊髓的

参考例句：

• After three days in Japan,the spinal column becomes extraordinarily flexible.在日本三天，就已经使脊椎骨变得富有弹性了。
• Your spinal column is made up of 24 movable vertebrae.你的脊柱由24个活动的脊椎骨构成。

13 regain   

vt.重新获得，收复，恢复

参考例句：

• He is making a bid to regain his World No.1 ranking.他正为重登世界排名第一位而努力。
• The government is desperate to regain credibility with the public.政府急于重新获取公众的信任。