Vascodilation and vascoconstriction

[Graeme]

I was wondering what you know about the topic of vascodilation and vascoconstriction of certain races to cold temperatures as a means of cold adaptation.

I remember reading that certain desert dwelling Aborigines could survive freezing night temperatures because their bodies cycled blood from their core to their extremities in order to prevent frostbite. I am interested as I have the ability to do the same with my hands. It actually is unpleasant as the cycle involves the feeling of numbness followed by pins and needles, but I guess my hands won't turn black from frostbite.

I hope I am not going to hear it is a Neanderthal feature.

[Dr. Solar Wolff]

As I recall, a study was done with some fishermen from Norway and their hands adapted to the cold. I think Coon cited this somewhere. Also, a study was done in Norway in the 1970s in which college students were exposed to increasing cold without proper clothing as the winter progressed. The result was that they adapted also although I forget the mechanism. Sorry, no references.

[Graeme]

Thank you for you reply. I was not exactly thinking of acclimatisation to cold. I was thinking of the natural ability to stay warmer, have blood shunting in the extremities and a lower susceptibility to frostbite. I have travelled the world and stayed in some cold climate zones yet I seem to handle the cold better than the locals in Canada and the USA. I remember seeing a Neanderthal programme which stated that their features - the big nose, squat bodies, short arms/legs - were adaptations to cold and that unlike the moderns, the so called African moderns, the Neanderthals were comfortable at much lower temperatures. At university I was taught in physiology that a 70 kg naked man sitting still in an enclosed room would be a thermal balance at 28 deg Celius. I thought that was rather odd. At 28 deg Celius, naked or not, still or not, I would be suffering heat stroke. I do accept that cold tolerance is part of having a high UP inheritance.

[Dr. Solar Wolff]

The information I posted was based on increased blood flow to the areas which needed heat. This response may be learned to some degree. Also, Australian Aboriginies put in a cold container also diverted blood from the arteries to the cooler extremities through connections to the veins. Coon mentions this also.

[Milesian]

Although you might think it a good thing to shunt blood to your extremities in order to prevent frostbite, the ultimate effect though is that it will result in a far more rapid drop in your core body temperature as warm blood is being cooled at the surface, near the skin. This is exactly the same mechanism that your body employs when you are over-heating in order to cool you down. Therefore, when it's cold your body keeps blood away from your extremities in order to minimise loss of body heat.
As far as the body is concerned, frostbite is preferable to hypothermia.