How strange, I still have two arms

I woke up in the night last night and my left arm was completely numb from the elbow down... yep, it's always fun to hit yourself in the face with something rubbery in the dark and then realize the something is your own hand. :b

I apparently slept through the pins and needles, because I woke up again and all is well. Is anyone biologically savvy enough to know how a limb can lose enough circulation that the nerve cells stop functioning, yet recover completely once blood flow resumes? How are the cells staying alive? Is there microscopic damage that I just can't feel? I have this irrational conviction that my arm should have shrivelled and fallen off by now--though obviously I'm glad it didn't.