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No cold comfort this

What makes us feel cold is, of course, the absence of energy, or heat, which is essentially the vibration of molecules, writes Prakash Chandra.

india Updated: Dec 23, 2007 20:41 IST
Prakash Chandra

If the chill is getting to you, don’t blame the weather — blame biochemistry. Research published in the Journal of Neuroscience explains how ‘cold fibres’ that connect neurons near the spinal cord to nerve endings in the skin help us sense the cold. A protein called TRPM8 alerts these fibres when to relay cold signals up the spine to the brain.

What makes us feel cold is, of course, the absence of energy, or heat, which is essentially the vibration of molecules. As molecules lose energy, they vibrate less — and their temperature drops. Remember, the sun doesn’t shine much in northern latitudes at this time of the year. The air there radiates heat into space, and becomes very cold. Shifting winds bring this cold air to lower latitudes like Delhi. When this cold air drains heat from our skin molecules, we go ‘brrr’. The faster energy is drained away, the colder it gets. This is called the wind chill factor — a term coined by US scientist Paul Siple in 1941. Wind increases heat loss, making it seem colder than what the thermometer shows. If the temperature is, say, +1, a howling wind makes you feel as if it were –15, although water still doesn’t freeze!

Low temperatures impair body functions as nerve cells and finger muscles work slowly: 12ºC is critical for manual dexterity and 8ºC for touch sensitivity. Try tying a shoelace, or doing up an awkward button, with fingers that are clumsy with cold! But cheer up, low temperatures also weaken pain receptors, allowing ice packs on sprains to reduce the swelling and pain. When the skin temperature falls below 10ºC, blood vessels dilate and constrict alternately as the body tries not to lose heat from the extremities, while keeping the blood supply to the skin going. So our cheeks and noses turn red in frosty weather. And the lowest temperature you can endure? In still air, wearing light clothing, you start to feel the cold below 10ºC, before physiological responses like shivering (to increase body heat) kick in. Not that we would want to check it out in this weather.