What happens, step by step, when blood stops reaching the brain? · Grey Matter

Within about 10 seconds consciousness is lost, and within about 20 to 40 seconds the EEG goes flat, because neurons stop firing to conserve energy before ATP has fallen much.

What happens, step by step, when blood stops reaching the brain?

Within about 10 seconds consciousness is lost, and within about 20 to 40 seconds the EEG goes flat, because neurons stop firing to conserve energy before ATP has fallen much. Over the next minutes ATP runs out and the sodium-potassium pump stops, so potassium leaks out, sodium, chloride, calcium and water flow in, and the tissue undergoes a sudden, near-total depolarisation (anoxic depolarisation). Terminals then release glutamate that transporters can no longer clear, and calcium overload starts excitotoxic damage. Neurons kept depolarised for more than about half an hour are unlikely to recover even if the circulation returns.