Robert Wrote:
>>
Unlike warm blooded creatures (children included) they do not require a
'fixed' temperature to be maintained for their health.
<<
Actually this is a bit misleading, if you could measure the >>average<<
body temperature of humans it can fluctuate widely. Under cold conditions so
as to approximately control "central" temperature, blood is shunted away from
the periphery and this increases the insulating properties of the outer
tissue layer by a factor up to something like 1 clo. (The clo is aproximately
equivalent to the amount of clothing insulation needed to be comfortable in a
typical ~21C office environment.) So under these cold exposures the
extremeties and outer layers are much closer to cold ambient temperature than
to 37C. Dropping the average temperature greatly.
For example if you place your hands in really cold iced water the skin
temperature drops to something like 1-2C and then the temperature oscillates
as the blood vessels open up and close down through loss of vasoconstriction
control below 2C.
Arterial and venous blood vessels in the legs (and arms) are paired so as to
act as countercurrent heat exchangers thereby minimising heat loss, at the
expense of limb temperature (again dropping the temperature dramatically on
cold exposure.)
Even "central" temperatures vary from organ to organ, with high metabolic
rate organs like the brain and liver being warmer than other organs by
something approaching 1C.
The only time the average body temperature probably reaches something like
37C is under conditions somewhere above 28C or heavily clothed. This is
because for an unclothed body the minimum energy consumption environmental
temperature, is often something in the 28-33C range.
What happens with children, is they have a much smaller mass than adults so
their "thermal time constants" are much shorter than their parents, and they
cool down a lot quicker.
Regards,
Tim Hughes
emailTimHughes@xxxxxxxx
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