英語(yǔ)聽力文摘 睡覺時(shí)為何不打噴嚏
睡覺的時(shí)候不會(huì)打噴嚏
The signs are unmistakable: the eyes water, the chest heaves, the nose twitches, the body tenses, suspense builds until finally a sneeze blasts forth, concluding the drama. It's a momentarily paralyzing experience that can seize one at almost any time.
But try and recall if you've ever been jarred out of a peaceful sleep by an explosive sneeze. Chances are you can't, because, thankfully, we don't sneeze while we sleep. To understand why, first we need to know why we sneeze while we’re awake.
Sneezing is a reflex, which means that it's an uncontrollable physical response to an outside stimulus. When something, say a piece of dust or a strong odor, stimulates nerve endings in the lining of the nose, the stimulus travels to the central nervous system and is then routed back to the muscles of the face, throat, and chest.
Once stimulated, these muscles go to work and cause us to forcefully expel air from the mouth and nose. Or, in other words, we sneeze.
Because the nose lining tends to swell when we lie down, making it even more sensitive to sneeze-causing particles, it would seem that sneezing would be likely during sleep.
However, since there is little airflow in most bedrooms at night, and little movement to stir up dust and other particles, the nose is not bombarded by as many foreign particles as it is during the day.
Furthermore, the area of the brain responsible for the sneeze reflex relaxes while we sleep. So, even when a particle does touch the nose lining, the brain doesn't notice, and we don't sneeze.
眼睛濕潤(rùn)，胸部隆起，鼻子一陣抽搐，身體緊繃，(身體)就這樣待定著，到最后一個(gè)噴嚏響起，像是演了一出戲劇!這使得人的身體短暫麻痹，它幾乎可以在任何時(shí)間讓一個(gè)人給緊縮。
但是，試想你曾經(jīng)有過在安詳?shù)乃咧斜灰粋€(gè)突然的噴嚏給震醒的情況嗎? 你是不會(huì)有的，因?yàn)楹軕c幸，我們?cè)谒X的時(shí)候不會(huì)打噴嚏。要理解其原因，我們首先需要了解為什么我們會(huì)在醒的時(shí)候打噴嚏。
打噴嚏是一種反射，也就是說它是一種生理對(duì)外界環(huán)境的反應(yīng)，不可控制。有時(shí)候，像一顆塵?；蛞还蓮?qiáng)烈的味道刺激了鼻子里的神經(jīng)末梢，這個(gè)刺激就會(huì)到達(dá)中樞神經(jīng)系統(tǒng)，繼而再返回到臉部、喉嚨和胸部的肌肉。
這些肌肉一旦被刺激，它們就會(huì)運(yùn)動(dòng)，導(dǎo)致我們強(qiáng)有力的排出口腔和鼻子里面的空氣。或者，換句話說就是打噴嚏。
因?yàn)樵谖覀兲上碌臅r(shí)候，鼻子里面部分趨于隆起，這使得它對(duì)引起打噴嚏的微小顆粒更加敏感。這樣看來(lái)，似乎在睡覺的時(shí)候更容易打噴嚏。
然而，由于我們的臥房里在晚上幾乎沒有空氣流動(dòng)，也沒有什么運(yùn)動(dòng)會(huì)揚(yáng)起灰塵及其它微粒，所以就不會(huì)有像白天那么多外界微粒來(lái)刺激我們的鼻子。
而且，當(dāng)我們睡覺的時(shí)候，腦袋中負(fù)責(zé)打噴嚏反射的區(qū)域也休息了。所以，即使有微塵碰觸了鼻子內(nèi)部，大腦也沒意識(shí)到，我們就不會(huì)打噴嚏。
