真“冷”知识！人们原来是这样感觉到“冷”的……

户外出行，你可能会感到冷风已穿透外套，脸颊等衣料遮掩较少的身体部位备受侵袭。为了探究我们的身体如何对寒冷做出反应，首先要搞清楚我们是如何感觉“冷”的。

Going outdoors, you may feel the cold wind trying to penetrate your coat, hitting body parts covered by little material – such as the face. To explore how our bodies respond to coldness, let’s first explore how we feel “cold”.

图源：东方IC

人类的皮肤粘膜表面遍布一种名为TRP的温度感知神经感受器，会对环境里的刺激信号产生反应。这些刺激信号可能包括压力、冷热以及化学刺激等。而大脑为感知寒冷，使用了一种名为TRPM8的低温感受器。

Human skin is filled with temperature-sensing nerve receptors named TRP, and they receive stimuli from the environment. Such stimuli may be pressure, cold, heat, or chemical, etc. To sense cold, the brain uses a kind of receptor called TRPM8.

研究人员在2002年首次研究出TRPM8，并发现10℃至30℃的低温（相比正常体温）和薄荷醇均是其活化信号。也正是因此，我们会觉得薄荷味的牙膏让口腔变得更冰爽、清新。TRPM8受到刺激时，会向大脑发送电信号，而大脑将这个信号理解为“冷”。

Scientists first studied TRPM8 in 2002, discovering that its stimuli include a temperature between 10 C and 30 C and menthol. This is also why mint-flavored toothpaste can make our mouths cooler and fresher. When the TRPM8 is hit by stimuli, it sends an electric signal to the brain which understands the signal as “cold”.

图源：VCG

随后身体会通过不同的方式，保护自身免受寒冷。据美国生命科学网报道，在感到低温后，身体会减缓肌肉和神经系统的活动，从而减少热量损失。

The body then protects itself from the cold through different means. According to Live Science, the body slows down its muscles and the nervous system. In this way, it reduces heat loss.

寒冷还会导致血液流动减少。身体首先会减少皮肤和四肢(包括手指、手和脚)的血液流动，因此这些部位会先感觉到冷。

The cold also leads to less blood flow. The body will first reduce blood flow at the skin and the body’s extremities, including the fingers, hands and feet. This is why these parts tend to feel cold first. 

美国陆军环境医学研究所的约翰·卡斯特拉尼在接受美国生命科学网采访时表示:“身体试图限制向外输送血液，以此减少向环境中释放热量。”

“We try to limit how much blood we send out there, so it limits how much heat we put into the environment,” John Castellani at the US Army Research Institute of Environmental Science told Live Science.

为了恢复体温，身体往往通过肌肉和器官的抖动来产生热量，这就是我们通常说的“寒战”。打冷战虽然可能没法产生多少热量，但更像是对人们的一种警告。在极端情况下，身体可能无法保持内部核心温度，就会导致冻伤等伤害。

To bring the body’s temperature back up, the body tends to produce heat itself by allowing muscles and organs to shake, more commonly known as shivering. Although this attempt may not be effective, it is more like a warning to people about the cold. In extreme cases, the body may be unable to maintain its core temperature inside, leading to injuries such as frostbite.

来源：21世纪英文报