Why does hitting your funny bone feel so horrible? - Cella Wright

譯者: Lilian Chiu 審譯者: Alexis Young

Whatever you were doing, there was no way to anticipate what came next.

無論你在做什麼，都無法 預測接下來會發生什麼。

The back of your elbow smacked against a hard surface

你的手肘後側撞上堅硬的物體，

and the impact sent a sensation so distinctly disquieting

這撞擊帶來一陣非常不適的感覺，

shooting down your arm that it took several moments to regain composure.

這感覺傳遍整隻手臂， 好一會兒才平靜下來。

So, why does hitting this spot on your elbow—

所以，為什麼撞到手肘的這個點——

often referred to as your funny bone— feel so weird?

通常被稱為麻筋—— 感覺會這麼怪異？

Well, to start, your elbow is one of the most complicated joints in your body.

嗯，首先，

手肘是身體中最複雜的關節之一。

It's where your upper arm bone, the humerus,

在這裡，上臂骨，即肱骨，

meets the two bones of your forearm.

與前臂的兩根骨頭相連。

Three main nerves run through your elbow.

有三條主要神經穿過手肘。

One of them, the ulnar nerve, is particularly relevant for our purposes.

其中之一是尺神經， 和我們要討論的主題特別相關。

Your ulnar nerve is composed of both sensory and motor nerve fibers.

尺神經是由感覺 和運動神經纖維組成。

It extends from your spine to the tips of your fourth and fifth fingers,

它從脊椎延伸到第四隻 和第五隻手指的指尖，

providing them with sensation along with swaths of your forearm and hand.

讓這兩隻手指以及前臂和手部的 一大片區域能夠有感覺，

So, say your little finger gets crushed by a car door.

所以，假設你的小指被車門夾到。

Sensory receptors in your pinky finger's tissues

小指組織中的感覺受器

register that unfortunate information

接收到那不幸的資訊，

and send electrical impulses up the ulnar nerve,

將電脈衝透過尺神經向上發送，

which are then processed in your central nervous system.

接著，中樞神經系統 會處理這些電脈衝。

This leads to the perception of acute, sharp pain,

這會導致銳利的劇痛，

followed by aching.

之後還會持續疼痛。

So that's how your ulnar nerve generally works.

這通常就是尺神經運作的方式。

But your elbow has an anatomical quirk that leaves your ulnar nerve vulnerable

但手肘有個解剖學上的特性，

讓尺神經很容易透過 另一種不同的方式啟動。

to getting activated in a different way.

Along almost all of its length, your ulnar nerve is protected,

幾乎整條尺神經從頭到尾 都有被保護起來，

hidden beneath muscle, fat, and bone.

藏在肌肉、脂肪，和骨骼底下。

Thankfully, this is generally true of your nerves.

還好神經通常都是這樣子的。

But when your ulnar nerve reaches your elbow,

但是當尺神經到達手肘時，

it runs beneath the bony bump at the bottom of your humerus,

它會穿過肱骨底部突起的下方，

named the medial epicondyle,

即所謂的肱骨內上髁，

and it passes through a tunnel of ligament and muscle tissue

它會通過肘隧道，那是一條 由韌帶和肌肉組織組成的隧道。

called the cubital tunnel.

When you bend your elbow,

彎曲手臂時，

your ulnar nerve gets flattened against the medial epicondyle

尺神經就會被壓扁在內上髁上面，

and the protective tissue in the area gets displaced,

而該區域的保護組織就會移位，

bringing the nerve especially close to the skin's surface.

讓神經特別接近皮膚表面。

In this position, the ulnar nerve is covered only by skin

在這個位置，覆蓋尺神經的

就只有皮膚及肘管的韌帶組織，

and cubital tunnel ligament tissue,

making it perhaps the longest area of semi-exposed nerve in your body.

讓它成為可能是體內 最長的半暴露神經，

So, when the area is struck at the right angle with enough force,

因此，當足夠的力量 從特定的角度撞擊該區域時，

something interesting happens.

就會發生有趣的現象。

Instead of the sensation simply activating peripheral receptors

並不是單純由感覺 啟動周圍神經受器，

that send electrical signals along your ulnar nerve,

再由受器沿著尺神經傳遞電訊號，

the nerve's fibers are stimulated directly.

反而變成是神經纖維直接受到刺激。

This is why hitting your so-called funny bone hits different.

這就是為什麼撞到所謂的 麻筋時感覺會很不同。

The exact mechanisms aren't yet fully understood.

我們還未完全了解確切的機制。

But the impact alters the ulnar nerve's signaling,

但這種撞擊會改變 尺神經的訊號發送，

perhaps by causing a proliferation of nerve signals,

可能會造成神經訊號激增，

leading to that intense pins-and-needles sensation

導致那種強烈的針刺感，

called transient paresthesia,

稱為暫時性感覺異常，

which radiates down the length of your arm.

它會放射到整隻手臂。

In rare cases, whacks to this special spot

在極少數情況下，擊中這個特殊的點

have led to temporary loss of consciousness,

會導致暫時失去意識，

perhaps because a hard enough strike could disrupt nerve signaling

可能是因為夠用力的撞擊 可能會打斷神經訊號發送

and blood flow.

和血流。

In addition to these more immediately distressing moments,

除了這些會讓人立即 感到不適的時刻之外，

regular bent-elbow activities are thought to put pressure

經常需要彎曲手肘的活動

也會隨時間帶給尺神經壓力。

on the ulnar nerve over time.

Ulnar nerve entrapment is a relatively common condition.

尺神經壓迫症是種相對常見的病症。

It happens when the ulnar nerve becomes compressed and obstructed,

當尺神經被壓迫和阻礙時就會發生，

most commonly with the cubital tunnel.

最常發生的部位是肘隧道。

The result of this chronic ulnar nerve pain can be persistent paresthesia,

這種慢性尺神經疼痛 可能會造成持續的感覺異常，

as well as weakness in the forearm and hand.

伴隨前臂和手部的無力。

In the hopes of preventing such conditions,

為了預防這種病症，

doctors recommend conscientious elbow usage.

醫生建議謹慎使用手肘。

That includes stretching your arms and straightening your elbows,

那包括伸展手臂和伸直手肘，

and generally taking breaks that help provide regular relief

通常，休息有助於提供定期的緩解

and maximal blood flow to your ulnar nerve.

並讓尺神經的血流能達到最大。