What does oxygen actually do in a neuron, and why does losing it stop the brain within seconds? · Grey Matter

Oxygen accepts the electrons at the end of the mitochondrial transport chain and becomes water; that last step keeps the chain moving, the chain pumps protons, and the proton flow drives ATP synthase.

What does oxygen actually do in a neuron, and why does losing it stop the brain within seconds?

Oxygen accepts the electrons at the end of the mitochondrial transport chain and becomes water; that last step keeps the chain moving, the chain pumps protons, and the proton flow drives ATP synthase. Without oxygen the chain jams within moments, and the brain has almost no stored oxygen and little stored fuel to fall back on. When blood flow stops completely, consciousness is lost in about 10 seconds and the EEG flattens within about 20 to 40 seconds, as neurons go quiet to save energy. Over the following minutes ATP runs out, the pumps fail and the ion gradients collapse, which starts the damage.