Eli5 why do people stop functioning altogether when having such issues as heart attack?


Coming from a place of seeing a video where a person had a cardiac arrest and they went from working out to dropping on the floor without a single body part movement in like a second or two.


Why it’s not a gradual process, why it’s seeming from 0 to 100%? What happens?

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2 Answers

Anonymous 0 Comments

Once the heart stops functioning, the blood flow stops, and the brain no longer gets any oxygen. The brain’s response to that is to shut down immediately, both to reduce oxygen requirements and to render the body horizontal, since in many cases that improves blood flow. In case of cardiac arrest, obviously, those measures are futile and the brain simply dies unconscious in a few minutes.

Anonymous 0 Comments

The brain consumes a *huge* amount of oxygen. About 2% of your body weight is responsible for about 20% of all the oxygen you consume. So when blood flow to the brain stops and it immediately identifies that the amount of oxygen being supplied to it is not enough to sustain it. So within a matter of seconds, the brain shuts down to conserve energy. Despite this, if 3 to for 4 minutes go by without restoring oxygen supply, the brain will be severely and permanently damaged and death wouldn’t be uncommon at this stage.