Wednesday, January 8, 2014

What effect does extreme cold have on the human body?


America is currently shivering through a record cold spell – icy storms and wind chill that has brought temperatures tumbling down to -57C (-70F). What effects does such extreme cold have on the human body?  

The polar vortex currently sweeping across the North American continent is bringing with it scenes usually associated with the Arctic or Antarctic. Massive snowfall and violent winds have plummeted temperatures down to record lows. In some areas of the US, such as the state of Indiana, all but essential emergency vehicles are banned from the roads. People are being urged to remain inside in the warm.

The human body is not designed for polar cold – most of us live in temperate and tropical climes, where the mercury rarely dips below freezing. There are populations that have adapted to polar extremes – like the Inuit in Arctic Canada and tribes like the Nenets in the north of Russia – but the vast majority of Homo sapiens has no experience of living in such sub-zero temperatures. And while our ingenuity and expertise has allowed us to create clothing to withstand all but the most violent Arctic blizzards, polar survival is all about keeping out of the most fearsome cold unless you absolutely have to.

What happens when we get cold? The human body has several defence mechanisms to try and boost our core temperature when it gets chilly. Our muscles shiver and teeth chatter. Our hairs rise and our flesh forms “goosebumps” – a kind of evolutionary echo from the times when our ancestors were covered in fur. The hypothalamus, the gland in the brain that acts as your body’s thermostat, stimulates these reactions to keep the body’s vital organs warm, at least until it can find some kind of warmth and shelter.

The hypothalamus’s mission is to keep the core warm at all costs – sacrificing the extremities if need be. That’s why we feel pins and needles in our fingers and toes in extreme cold – the body is keeping its warm blood close to the centre, constricting blood supply in the outer regions such as the end of our limbs. In extreme cold, and especially if bare skin is open to the elements, this effect can end in frostbite. Blood flow is reduced, and the lack of warm blood can lead to tissue freezing and rupturing.

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