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Name: Nathan
Status: student
Grade: N/A
Location: VA
Country: N/A
Date: 5/31/2005

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?"

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.

Van Hoeck

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