I Wonder...

...when my hands and feet fall asleep in the middle of the night, and I wake up to shake them back to life, what is it that's really waking me up? Is it the fact that my extremitites are dying, and my body's trying to prevent me from losing limbs, or is it just that I have to get up and go to the bathroom, and it's a helpful coincidence that I can now get the blood flowing again?