Drakodan Posted:

I certainly believe in something spiritual, since I find it almost ridiculous to believe that our fleeting lives are all that there is

Why? I know it’s hard to conceive of the universe rolling on uncaring without us after we die, but it was all perfectly fine before we were born.

Drakodan Posted:

People can be revived from drowning [...] Yet, when people die good and proper, there’s no coming back. So, what disappears at that point?

The change is brain death. You can survive the oxygen starvation that comes as part and parcel of your heart/lungs ceasing function for a limited period of time before your brain cells start dying. But if that goes on too long, you die ‘for real’.

There’s actually some evidence that brain cells can survive oxygen starvation much longer than we previously thought, but the shock of oxygen returning can kill them… don’t remember if there was a remedy to that though… maybe reintroducing oxygen more slowly, but the whole thing would be fraught with risk – coming back from severe lack of oxygen normally means substantial brain damage, possibly to the point of being vegetative.

Drakodan Posted:

If heartbeat can be brought back, then why can’t the consciousness?

Because we don’t know how to repair or ‘jump-start’ a brain after it’s suffered severe damage. Once too many cells have died, and the connections they made are lost, it’s next to impossible to rebuild the neural web that made your brain function as a brain instead of a big mess of unconnected neurons.

Hearts are simpler – essentially just a specialised muscle, so it can lose some cells, even a lot of cells, and the ones that are left can still do their job. Brains fundamentally break if you kill off too many of their cells.