system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we die instantly when our heart stops? Why don't we asphyxiate from lack of oxygen from blood no longer circulating?

I know this sounds extremely dumb but I've always wondered about this. I can understand dying via shock if shot or stabbed in the heart. But when it just stops because of old age or sickness, why is death instant? They say you can live about 5 minutes without oxygen so why don't we die after about 5 minutes since blood is no longer circulating?

Like I said, I know this sounds really dumb because it's basically like "well because your heart stopped, duh!". But why does it stopping kill you instantly instead of brain death through suffocation?
gpt
You don't die instantly; people with a totally stopped heart often die, but it is possible if the heart resumes in a timely manner you'll survive.

There's a distinction between alive and conscious, though. A total stop in blood flow will make you pass out really quickly; in fact a sudden decrease in blood flow to the brain can easily cause one to faint even without the heart stopping.