Question

The body's ability to maintain a relatively constant internal environment is called homeostasis. This stability can be challenged by

Answer 1

I'm guessing that you are asking of outside factors?

I'd say temperature for one, because it forces homeostasis to work in overdrive to maintain that constant internal environment.

If that's what your question is asking, think of other outside forces that would affect it. Blood sugar levels (from what you eat, etc) would force homeostasis to be maintained... things like that:)
hope that helps somewhat!!:D