Eternal Question

While getting a trim today, I was confronted once again with an eternal question that has, fittingly, bothered me for quite a while. They always say that hair with split ends doesn't grow- but why not? Hair, I think, grows out of follicles from the scalp and hasn't got any nerves, so how the heck does the top of the hair know if the bottom has got split ends or not? And if there's something deeper wrong with hairs with split ends, then how would a trim help anything?
So I decided to turn the question over to the combined brain-power of my family and see what they could provide. Good luck!