Quote:
The pressure squeezes nerve pathways so that the nerves can't transmit electrochemical impulses properly. Nerve impulses carry sensation information from nerve endings in the body to the brain, as well as instructions from the brain to the parts of the body. When you interfere with this transfer by squeezing the nerve pathways, you don't have full feeling in that body part, and your brain has trouble telling the body part what to do.
This pressure can also squeeze arteries, stopping them from carrying nutrients to body cells. Without these nutrients, the nerve cells may behave abnormally, which can further interfere with communicating bodily sensations. [/b]
It seems that it is a combination of both blood loss and nerve impulses being blocked, although I believe it is mostly the nerves that cause the absolute loss of communcation - not the blood.