B1 中級 美國腔 171 分類 收藏
開始影片後,點擊或框選字幕可以立即查詢單字
字庫載入中…
回報字幕錯誤
The American poet Ogden Nash said, "Happiness is having a scratch for every itch."
While scratching can feel pretty good, we all know what happens next.
When considering scratching an itch, it may be better to follow the old Yiddish proverb:
"A quarrel is like an itch; the more you scratch, the more it itches."
There are plenty of things that cause that irritating, unpleasant, itchy sensation.
But why do we itch in the first place?
The itch sensation, also known as pruritus, is not the most pleasant thing,
but it evolved for a good reason.
Stretched out, your skin covers about 20 square feet, the biggest organ you have.
Your other organs on the inside are protected by your immune system, but skin is your first line of defense,
the wall that guards the human realm, exposed to the elements,
and it's got a unique way to deal with different types of threats.
Where there's an itch, there's a desire to scratch, often an unconscious desire.
This reflex likely prompted our outdoor-dwelling ancestors to remove dead skin or parasitic threats
and other irritating things like thorns and allergens.
And much like yawning, being itchy is thought to be contagious,
as some of you may be noticing right about now.
We're social animals, so watching some infested tribe mate get their scratch on
could have given us a head start to get rid of those parasites.
So, we know the purpose of itch.
But what happens inside our bodies that makes it feel different from other sensations like pressure or heat?
Turns out, we don't know all the pieces to the itch puzzle yet.
Up until about a decade ago scientists thought itch was just a dialed-down, less intense version of pain.
When something makes contact with our bodies, nerve endings in the epidermis, the outermost layer of our skin,
relay this information through electrical and chemical messages, up the spine and to the brain.
Different stimuli activate different nerve pathways and cause different sensations in our brains.
Light touch might feel nice.
A punch to the face will probably hurt.
We now know that there's special itch-specific circuitry in our nervous systems,
involving its own chemicals and cells.
And we share one universal response to itching: scratching.
And boy, does it feel good!
But, why?
Scratching is technically a form of pain.
I mean, the name of a small wound that breaks the skin is a scratch.
Scratching causes a low-level pain signal to the brain that masks and overrides the itch signal,
which is why slapping, pinching, and pressing itchy regions also gives you relief.
Remember that the next time your mom tells you not to scratch.
Your brain responds to pain by triggering the release of chemicals at the irritated site,
which tunes down the painful sensation.
One of those relief-providing chemicals is serotonin, a neurotransmitter.
But that serotonin also makes it easier for the itch signal to be re-triggered.
So, the itch nerves fire again and you get even itchier!
Scientists call this constant loop of itching and scratching "the itch-scratch cycle,"
very clever, and it can be maddening.
In extreme cases, damage to itch-sensing nerves can cause itching without an actual stimulus.
This is the kind of itch that scratching can't help.
People who have recovered from shingles, a virus infection that affects your nervous system,
can be left with an unexplainable, never-ending itch once the rash recedes.
One women had such an itchy scalp after healing from shingles.
she scratched straight through to her brain.
What?
So, what can the rest of us do to avoid scratching and itch?
Itchy ailments have been documented throughout history,
and humans have found some pretty clever ways to find relief.
The Greeks and Romans had mineral baths and animal fat.
The Persians used silver.
Menthol soothed itchy skin in ancient China, and camphor, a chemical from Evergreen trees
historically used to make explosives, has been soothing itchy skin since the 13th century.
Today we also have anesthetics, which numb the skin of all feeling,
counterirritants like capsaicin, extracted from chili peppers,
and antihistamines and steroid creams, just to name a few.
But since itchiness can be caused by so many things, there isn't a one-size-fits-all remedy.
Luckily, with so many treatments to choose from, at least you don't have to start from scratch.
If you're itchy, just remember: unlike beauty, itch doesn't run only skin deep.
It's a sensation that reaches from the epidermis to the brain.
The origins of that itch you might be feeling right now extend way back on the evolutionary tree,
and we've only scratched the surface of knowing how it all works.
Stay curious!
Oh, and here is a video challenge for you: re-watch this without itching yourself uncontrollably.
Hey guys, I wanted to tell you about another great channel. It's part of the PBS Digital Studios family.
Check out Above the Noise. It's a channel that cuts through the hype about the news
so that you can understand the facts behind it and how they relate to your life.
I recently helped them out on an episode about why only some countries have nuclear weapons.
We'll leave a link down in the description, so you can check them out.
提示:點選文章或是影片下面的字幕單字,可以直接快速翻譯喔!

載入中…

這裡癢那裡癢!到底為什麼會發癢?! (Why Do We Itch?)

171 分類 收藏
April Lu 發佈於 2019 年 3 月 15 日    Patrick 翻譯    Evangeline 審核
看更多推薦影片
  1. 1. 單字查詢

    在字幕上選取單字即可即時查詢單字喔!

  2. 2. 單句重複播放

    可重複聽取一句單句,加強聽力!

  3. 3. 使用快速鍵

    使用影片快速鍵,讓學習更有效率!

  4. 4. 關閉語言字幕

    進階版練習可關閉字幕純聽英文哦!

  5. 5. 內嵌播放器

    可以將英文字幕學習播放器內嵌到部落格等地方喔

  6. 6. 展開播放器

    可隱藏右方全文及字典欄位,觀看影片更舒適!

  1. 英文聽力測驗

    挑戰字幕英文聽力測驗!

  1. 點擊展開筆記本讓你看的更舒服

  1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯,不妨使用「俚語字典」,或許會讓你有滿意的答案喔