On: Biological Miracle – Wood Frog

[telgareith]

my poor knowledge of biology says it's a deeply unsatisfying "heart beats when enough of the body has thawed for it to beat."

If the heart depends on the brain at all in frogs.

[nine_k → telgareith]

It doesn't, even in humans. There is an independent circuit of special muscle cells right on it that keeps it beating.

So starting and stopping the heart in a controlled manner is pretty interesting, because it has to be well-timed, and there are few obvious and reliable inputs to control it, especially when thawing.

[8n4vidtmkvmk → nine_k]

Why doesn't my heart keep beating if my brain dies then? Or would it?

[kampsun → 8n4vidtmkvmk]

I understand that it would keep beating until you are provided oxygen. That’s my understanding understanding of brain death at least.

[oharapj → 8n4vidtmkvmk]

Probably because the brain controls breathing and so the oxygen runs out quickly

[8n4vidtmkvmk → oharapj]

I was going to say that's silly, but I guess we need to be able to hold our breath sometimes.

[telgareith → nine_k]

"Even in humans"- thats a pretty steep assumption.

I am fully aware that if the human heart is severed from the brainstem it will develop A rhythm.

But what about other mammals? Dunno. Not going to assume.

Theres also the tidbit that frogs are not mammals.

[nine_k → telgareith]

The point is that whatever control a frog heart may have, it's not cerebral. It must be a very low-level circuit, which can be modulated from outside, but which remains autonomous.