At 02:51 PM 4/1/98 +1000, you wrote:
>I agree with your comment about the temperature effects of the blood supply
>being cut off to parts of the body. However, I suspect that the drop in
>temperature in different parts of the body of penguins, as described in the
>Nature (1997) article, is much greater in magnitude and rate than that
>experienced by human athletes. In addition, we established in earlier
>discussions that the penguin's heart rate slows down considerably during a
>dive, whereas an athlete's would increase during exercise. Thus a penguins
>metabolic rate would be decreasing, and an athlete's would be increasing.
>Therefore, the physiological responses of a penguin during a dive appear to
>be some of the early signs experienced by animals going into torpor.
>
>Are you aware of any data which show temperatures in different regions of an
>athlete's body during exercise, for comparison with penguins?
No I don't have this data close at hand but it is probably not relevant to
compare what happens when a person is running to what happens when a
penguin dives. The heat exchange through body tissues would not be the
same because of the insulation provided by the airsacs. Also, simply
immersing a human in water reduces the heart rate. This is due to the
water exerting extra venous pressure and thus cardiac return. When
hypothermic humans lost at sea are retrieved from the water it must be done
carefully so as not to induce a sudden hypotensive shock to the circulatory
system.
So in summary I also don't buy the reduced heart rate as an indicator of
decreased metabolism. You can explain it other ways. The cardiac output
could still be the same or even increased if only the brain and muscles are
receiving the bulk of the blood flow. This is the key : heart rate does
not = cardiac output.
Of course I could be totally wrong and don't mind being proved so.
Can anyone remember how we started this discussion ???????
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Shane Raidal BVSc PhD MACVSc
Lecturer in Veterinary Pathology
Veterinary and Biomedical Sciences
Murdoch University phone: +61 8 9360 2418
Perth,WA, 6150 fax: +61 8 9310 4144
Australia
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