Question:
Dear Sir or Madam,
I have a question from my 10th grade biology class that I would love to
have answered. The question is "Does an endothermic animal's heartrate
raise when the outside temperature goes up?"
Replies:
The human body has all kinds of feedback controls that keep it in
homeostatic balance. It is true that if you lower the body's temperature, as
in the case of hypothermia, the heart rate will slow down. This is also one
reason why if someone "drowns" in cold water, they are more likely to be
revived because the metabolism slows down also and oxygen isn't used up as
fast. If the opposite is true, ie. drowning in a hot tub, metabolism speeds
up and oxygen is used faster. If you sit in a hot tub and your body warms up
very quickly, you may experience an increase in heart rate-for awhile. You
may also notice that you have a more rapid heartbeat when you have a fever.
You have sensors in your aorta and medulla of your brain that control your
heart rate. After the initial increase, these sensors will send a message to
the pacemaker in your heart to slow it down and bring it back to normal. If
this were not true, that would mean that people who live in warmer climates
would have faster heartbeats than people who live in cold climates. And I
don't think that happens.
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