[@FunnyGuy][@King Tai][@Wick]
And don't forget there is a real life situation where some people simply can't feel pain....it has various degrees where pain is at one end and the opposite end is not feeling anything at all

It has to do with pain receptors. If those are not functioning there is noting to tell you if you just stepped on a piece of glass. 

Generally if everything functions all your nerves and receptors function. If they aren't that's when you get people who can't feel pain or anything at all.

It's fascinating 


Edit: found a video yay
http://youtu.be/wMxzRpImPgo