What exactly occurs when you faint from lack of oxygen to make your body start breathing again?

Question

This is a question I don’t know how to ask Google about.

In: Biology

Answer 1

What causes the breathing reflex is a build-up of carbon dioxide, *not* a lack of oxygen. That’s actually a pretty important distinction–it means if you were put into a room which had no oxygen in it, but instead was filled with some other gas that wasn’t immediately fatal (say, nitrogen), you would suffocate without any of the normal warning signs, because no oxygen means your body can’t make carbon dioxide. No CO2, no “I’m suffocating!” warnings.