What makes spicy food affect us, creating the "hot" feeling?

Factual Questions
1

What do the elements in something like Wusabi, or Chilly Peppers, or what have you, actually do to create this “hot” sensation we feel in our mouths, noses, throats, and heads? Anatomically speaking, what is affected within us to create such a reaction, and why?

2

Welcome to the Straight Dope Message Board.

I was going to be a smart ass and tell you to search the archives, but I tried, and unless you knew to look for “capsaicin” it wasn’t that obvious.

It’s covered in a staff report:

Are birds immune to hot pepper, enabling them to eat vast amounts and spread the seeds?

BTW, it’s “Wasabi” and “Chili”…

3

I was going to be a smart ass and tell you to search the archives, but I tried, and unless you knew to look for “capsaicin” it wasn’t that obvious.

         Ah, but you were a bigger smart ass for mentioning it, weren't ya? (-:

         Thanks for the info.
4

Oh ye of little faith in the Almighty Search Engine:

http://www.straightdope.com/classics/a1_346.html