Why do you colapse immediatly after your heart has stopped beating because of a heart attack and not a few minutes later after your body has run out of oxygen?
There is a delay, it just isn’t very long. Your brain needs a *lot* of oxygen all the time to function and will shut down (causing unconsciousness) within a few seconds of losing access to fresh oxygen (as happens when your heart stops.) Brain activity can continue in a limited way for a few minutes, but after that, it’s kaputt.
The only reason that you can maintain consciousness for any time at all after you stop breathing is that there’s air in your lungs that fresh oxygen can still be drawn from.
Minor quibble you instantly collapse on cardiac arrest (heart stop beating) not necessarily on heart attack (oxygen supply to part of heart cut off, usually a blocked coronary artery). Someone with a heart attack can be walking and taking, cardiac arrest very much not. And of course a heart attack can lead to cardiac arrest.
Have heart disease myself so very aware of this distinction!
Your brain needs a lot of energy to run, but it’s also the only organ that isn’t capable of producing its own energy. It is entirely dependent on oxygen and glucose being constantly fed to it.
The heart pumps the juice to the squash. If the pump suddenly stops working, it doesn’t matter if there’s good stuff in the juice if it can’t go anywhere.
This is different from a respiratory / airway issue where there’s plenty of juice going to the squash, it’s just not good juice.
I feel like it’s the same reason that some people faint when they get their blood drawn vs. don’t faint when they hold their breath. I think our brains need a lot of blood and so losing a significant amount (which happens quickly if your heart isn’t beating) causes you to lose consciousness (maybe as a way to preserve energy?)
Because it only takes a few seconds without oxygen to pass out. If your thinking about holding your breath remember that there’s still oxygen in your lungs and blood that takes time to get fully used up. When your heart stops (or someone cuts off blood to your brain) you instantly lose all oxygen delivery.