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  • You're standing at the ready inside the goal.

    你正站在球門內準備好了

  • When suddenly, you feel an intense itch on the back of your head.

    突然,後腦感到一陣強烈的癢

  • We've all experienced the annoyance of an inconvenient itch,

    我們都曾因為當下不方便處理的癢而感到煩躁不已

  • but have you ever pondered why we itch in the first place?

    但首先,你有仔細想過為何我們會覺得癢嗎?

  • The average person experiences dozens of individual itches each day.

    每天人們平均會感受到數十次癢的感覺

  • They can be triggered by all sorts of things,

    許多事物都能觸發癢的感覺

  • including allergic reactions,

    包括過敏反應

  • dryness,

    乾燥

  • and even some diseases.

    甚至是某些疾病

  • And then there are the mysterious ones that pop up for no reason at all,

    另外,還有一種神祕的情況是它毫無原因的突然出現

  • or just from talking about itching.

    或僅僅是談論癢也能觸發癢的感覺

  • You're scratching your head right now, aren't you?

    你現在正在抓你的頭,沒錯吧?

  • Anyhow, let's take one of the most common sources: bug bites.

    無論如何,我們先從最常見的觸發原因之一開始探討:昆蟲咬傷

  • When a mosquito bites you,

    當蚊子咬你時

  • it releases a compound into your body called an anticoagulant

    牠的口器會釋放名為「抗凝血劑」的混和物到你的身體中

  • that prevents your blood from clotting.

    避免你的血液凝結

  • That compound, which we're mildly allergic to,

    由於我們的身體對這個混和物輕微過敏

  • triggers the release of histamine,

    因此它會觸發組織胺的釋放

  • a chemical that makes our capillaries swell.

    組織胺是一種會讓我們的微血管膨脹的化學物質

  • This enables increased blood flow,

    微血管膨脹使得血流增加

  • which helpfully accelerates the body's immune response

    會加速當身體察覺到威脅時

  • to this perceived threat.

    所做出的免疫反應

  • That explains the swelling,

    這解釋了蚊子咬的地方會腫脹的原因

  • and it's the same reason pollen can make your eyes puff up.

    而花粉會讓你的眼周腫脹也是相同的原因

  • Histamine also activates the nerves involved in itching,

    組織胺也會刺激癢覺相關的神經

  • which is why bug bites make you scratch.

    這也是為什麼蟲咬會讓你想抓癢

  • But the itchy sensation itself isn't yet fully understood.

    但是目前癢覺本身還沒被完全理解

  • In fact, much of what we do know

    事實上,我們所知很多有關癢覺的知識

  • comes from studying the mechanics of itching in mice.

    都來自於老鼠體內癢覺機制的研究

  • Researchers have discovered that itch signals in their skin

    研究人員發現老鼠皮膚中的癢覺信號

  • are transmitted via a subclass of the nerves that are associated with pain.

    是從掌管痛覺相關的子神經轉換而來

  • These dedicated nerves produce a molecule called natriuretic polypetide B,

    這些專門的神經產生了一種叫"Natriuretic polypetide B"的分子結構

  • which triggers a signal that's carried up the spinal cord to the brain,

    這個分子會觸發訊號,經由脊髓傳到大腦中

  • where it creates the feeling of an itch.

    因此大腦就會產生癢的感覺

  • When we scratch, the action of our fingernails on the skin

    當我們搔抓時,指甲在皮膚上的動作

  • causes a low level pain signal that overrides the itching sensation.

    會產生可以壓制癢覺的低程度痛覺訊號

  • It's almost like a distraction, which creates the sensation of relief.

    它就像是干擾一樣,使得癢的感覺得到舒緩

  • But is there actually an evolutionary purpose to the itch,

    然而,癢這件事和演化目的有關嗎?

  • or is it simply there to annoy us?

    還是它僅僅是一個讓我們煩躁的現象呢?

  • The leading theory is that our skin has evolved to be acutely aware of touch

    目前主流的理論是我們的皮膚已經進化到可敏銳地感知觸覺

  • so that we're equipped to deal with risks from the outside world.

    使得我們能夠處理來自外界的危險

  • Think about it.

    試著想想看

  • Our automatic scratching response would dislodge anything harmful

    我們對癢的自動搔抓反應可以驅逐任何可能

  • that's potentially lurking on our skin,

    對我們的皮膚有潛在傷害的事物

  • like a harmful sting,

    像是傷人的刺

  • a biting insect,

    正在咬我們的昆蟲

  • or the tendrils of a poisonous plant.

    或是有毒植物的卷鬚

  • This might explain why we don't feel itching inside our bodies,

    這或許解釋了為何我們不覺得身體內部會癢

  • like in our intestines,

    像是我們的腸子

  • which is safe from these external threats,

    它們不會受到這些外在威脅

  • though imagine how maddening that would be.

    想想看,如果腸子會受到這些外在威脅,那會是多讓人惱怒的事情

  • In some people, glitches in the pathways responsible for all of this

    對某些人來說,負責傳送感覺的神經路徑上的干擾

  • can cause excessive itching that can actually harm their health.

    可能會導致過度搔癢進而影響健康

  • One extreme example is a psychological condition called delusory parasitosis

    其中一個極端的例子就是名為「寄生蟲妄想症」的心理現象

  • where people believe their bodies are infested with mites or fleas

    它會讓人覺得他們的身體佈滿大量的蟎蟲和跳蚤

  • scurrying over and under their skin,

    並且在皮膚底下亂竄

  • making them itch incessantly.

    讓他們不斷的發癢

  • Another phenomenon called phantom itching

    另外一種現象則稱為「幻肢搔癢」

  • can occur in patients who've had amputations.

    這個現象常發生在曾經做過截肢手術的病人身上

  • Because this injury has so severely damaged the nervous system,

    由於他們所受的傷害對該神經系統造成嚴重損壞

  • it confuses the body's normal nerve signaling

    使得身體中正常的神經訊號產生混淆

  • and creates sensations in limbs that are no longer there.

    並讓早已不存在的肢幹產生感覺

  • Doctors are now finding ways to treat these itching anomalies.

    醫生們也在尋找這種異常癢覺的治療方法

  • In amputees, mirrors are used to reflect the remaining limb,

    對於已截肢的人,會利用鏡子將其仍存在的肢幹反射到已被截肢的那側

  • which the patient scratches.

    並且搔抓那仍存在的肢幹

  • That creates an illusion that tricks the brain

    那樣做產生了欺騙大腦的幻象

  • into thinking the imaginary itch has been satisfied.

    讓大腦認為幻肢的癢覺已經滿足了

  • Oddly enough, that actually works.

    說也奇怪,這個方法確實有用

  • Researchers are also searching for the genes involved in itching

    研究員們也正在研究和癢覺有關的基因

  • and developing treatments to try and block the pathway of an itch

    並發展在某些極端狀況下阻止癢覺

  • in extreme cases.

    的治療方法

  • If having an unscratchable itch feels like your own personal hell,

    如果你認為不能抓的癢是地獄的話

  • Dante agreed.

    但丁是同意這個觀點的

  • The Italian poet wrote about a section of hell

    這位義大利詩人描寫的其中一個地獄類型

  • where people were punished by being left in pits to itch for all eternity.

    就是人們被留在一個深坑內受著永恆的搔癢作為處罰

You're standing at the ready inside the goal.

你正站在球門內準備好了

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B2 中高級 中文 美國腔 TED-Ed 皮膚 神經 產生 身體 現象

【TED-Ed】為什麼會覺得癢?癢到底是怎麼來的? (Why do we itch? - Emma Bryce)

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    Jost Lin 發佈於 2017 年 07 月 26 日
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