你知道嗎？為什么鼻子每次只堵一邊？

Though you may not pay attention to it unless you're sick, you're always breathing more heavily from one nostril than the other.

除非生病了，否則你可能并不會(huì)注意到，你的一個(gè)鼻孔總是比另外一個(gè)呼吸更費(fèi)力。

During the day, the sides switch and the other nostril goes into 'work mode', but why?

一天之中，兩邊的鼻孔可能會(huì)交換，另一側(cè)的鼻孔進(jìn)入“工作模式”。但這是為什么呢?

This process is automated by the aptly named autonomic nervous system, which is the same system that controls many things your body does all by itself such as digestion and heart rate.

這一過程由自主神經(jīng)系統(tǒng)自動(dòng)控制，這個(gè)系統(tǒng)也控制著你身體自動(dòng)運(yùn)轉(zhuǎn)的許多方面，比如消化和心率。

For your nose, this system controls your 'nasal cycle', so that each nostril operates effectively.

對(duì)你的鼻子而言，這一系統(tǒng)控制著你的“鼻子循環(huán)”，便于每個(gè)鼻孔有效工作。

The nasal cycle happens, according to the US National Library of Medicine, several times during the day, and is only brought to your attention if your nose is clogged up more than usual.

據(jù)《美國(guó)國(guó)家醫(yī)學(xué)圖書館》透露，鼻子循環(huán)一天會(huì)出現(xiàn)好幾次。只有當(dāng)你的鼻子比平時(shí)更堵的時(shí)候，你才會(huì)注意到這一點(diǎn)。

In order to open one side of your nose and close the other, your body inflates tissue with blood in your nose.

為了打開一邊的鼻孔、關(guān)閉另一邊，你的身體會(huì)讓鼻子里的組織充血膨脹。

"Increased blood flow causes congestion in one nostril for about 3 to 6 hours before switching to the other side. There is also increased congestion when one is lying down, which can be especially noticeable when the head is turned to one side," Jennifer Shu reports for CNN.

據(jù)美國(guó)有線新聞網(wǎng)的詹妮弗-舒報(bào)道：“血流增加會(huì)導(dǎo)致一邊的鼻孔堵塞3-6個(gè)小時(shí)，之后才會(huì)轉(zhuǎn)移到另一邊。人們躺下來的時(shí)候，鼻孔堵塞程度也會(huì)增加。人們將頭轉(zhuǎn)向一邊的時(shí)候，這一點(diǎn)會(huì)格外明顯。”

It's believed that this cycle helps round out your sense of smell. As Matt Soniak reports for MentalFloss, some smells are better picked up by fast moving air through your nose, while others take more time and are detected better with slow-moving air.

據(jù)稱，這種循環(huán)有助于豐富人們的嗅覺。據(jù)MentalFloss網(wǎng)站的馬特-索尼亞克報(bào)道說，某些氣味能更好地被鼻孔中快速氣流捕捉到，而其它氣味需要更多時(shí)間被慢速氣流捕捉到。

If one side of your nose is wide open and the other is slightly closed, you get all of the smells.

如果一個(gè)鼻孔張得很大，而另外一個(gè)鼻孔略微閉合，那么你就能夠聞到所有的氣味了。

The process also gives each side of your nose a break, since a constant stream of heavily flowing air can dry it out and kill off the small hairs that protect you from foreign contaminants.

這一過程也能讓你的兩個(gè)鼻孔稍微休息一下，因?yàn)槿绻粩嘤写罅靠諝饬鬟^鼻孔，會(huì)導(dǎo)致鼻孔干燥并損害鼻毛，鼻毛能夠保護(hù)你不受外來污染物傷害。

When you get sick, the whole process can become unbearable, because the one nostril that is effectively 'turned off' feels way, way more clogged than the other, Soniak says.

索尼亞克說，當(dāng)你生病的時(shí)候，這一過程會(huì)變得令人難以忍受，畢竟其中一個(gè)有效“關(guān)閉”的鼻孔會(huì)讓你感覺比另一側(cè)更堵。

Basically, the clogged-up feeling is just amplified by the cold.

基本上，感冒會(huì)使鼻子堵塞的感覺放大。

So the next time you feel like you're only breathing from one side of your nose, remember that it's a natural, automatic system working to keep you smelling properly, and to make sure your nose doesn't get dried out by a constant onslaught of dirty air.

下次，你感覺自己只能用一側(cè)鼻孔呼吸的時(shí)候，請(qǐng)記住這是一件很正常的事。你的自主系統(tǒng)正在幫助你恰當(dāng)?shù)芈劦綒馕?，并確保你的鼻子不會(huì)因?yàn)椴粩嗪粑a臟的空氣而變得干燥。