I had the following question on an exam of mine and I got it wrong, so I was wondering if someone could help explain the reasoning to me. Below I list my explanation.

An overheated and sick dog in a hot environment will have an impaired thermoregulatory response when its

(A) evaporative heat loss increases

(B) metabolic heat production decreases

(C) body temperature increases to match the environmental temperature

(D) blood vessels near its skin increase vasoconstriction

So here's how I approached this: A and B are clearly incorrect, as they aid the thermoregulatory response of the animal by allowing it to lose excess heat.

Thus, it comes down to C and D. I chose D because I thought that since vasoconstriction traps more of the heat inside the body, it would be counterproductive to what the dog actually needs (vasodilation). I'm assuming that the correct answer choice is C, but could someone please explain it to me?

Thanks in advance to all who reply :)


You're right, A and B both are normal thermoregulatory responses, so those can't be the right answer.

I'm guessing the rationale for C is that, if the dog's body temperature is increasing to match that of the hot environment, it must mean the dog has an impaired thermoregulatory response. It's kind of tautological.

But D also seems correct to me. If a dog is in a hot environment, and its blood vessels near the skin are constricting (say, because it's sick), that's counterproductive to the normal thermoregulatory response. If the dog isn't dilating its blood vessels near the skin, that's an impairment to the normal thermoregulatory response.

Perhaps the question is written wrong? Maybe D was supposed to say "vasodilation" instead of "vasoconstriction"? If this is a question written by a teacher I'd say you have a case for arguing it.

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    $\begingroup$ This is a question from Ch40 of Campbell's Biology, they seem to be getting at the fact that C is right because the dog is endothermic and only operates properly within a certain range of temperatures. For D, the argument is that since the environment is already hot, vasoconstriction to decrease heat interface is beneficial. $\endgroup$ – CKM Oct 28 '15 at 23:10
  • $\begingroup$ @Kendall - Such a helpful comment! Might you want to turn it into an answer? $\endgroup$ – anongoodnurse Oct 29 '15 at 3:36
  • $\begingroup$ Thank you everyone. I asked my teacher (since she's technically not the one who designs these questions) and she said that D is correct, so she rewarded me the points. $\endgroup$ – AleksandrH Oct 29 '15 at 10:07

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