Okay, say you need to sacrifice someone to Huitzilopochtli. As per the scriptures, you hold the victim down, rip open his chest, and cut out his heart while he’s still alive.
My question is: assuming no other medical procedures were observed, and you were working as fast as you could, how long would a human heart keep beating after you cut it out? Seconds? Minutes? Would it just go into cardiac arrest from the trauma, if not actually “dying” right away? Does it vary too much from person to person to give a meaningful answer?
Dr_Paprika: The SA node is a self-generating pace maker for the heart. It will make the heartbeat without any input from the brain/nervous system/rest of the body. The key issue here, as I see it, is blood supply. Once you cut the vena cava from the right atrium, the heart isn’t getting supplied with blood anymore. No blood = no oxygen. You won’t have long before the heart pumps out the blood that is already in the coronary artery and is no longer getting oxygen, so I’m going to say a few seconds, at best. I’m more willing to bet, though, that it won’t even make it as far as outside the chest completely before it stops.
I remember pretty clearly dissecting a live frog in high school biology, and its heart beat for quite a long time (at least a minute or two) after we removed it from the thorax. We were able to put it into a jar of saline solution and watch it propel itself around like a little jellyfish.
I will let the big science crew tell you about the details but salt will make muscle twitch.
As a TA in animal anatomy that was my favorite passtime. You sneak behind someone doing a disection and sprinkle some salt on it and the whole thing starts dancing. That doesn’t mean it is alive, though.
Maybe that’s the trick for human sacrifice priests. Wash your hands with brine before the show starts and the heart will beat.
The heart never beats for more than a few seconds after I remove it from my autopsy patients.
But seriously…we did get an excisional breast biopsy in the pathology lab awhile back that included a portion of skeletal muscle. That muscle (lacking intact innervation) twitched repeatedly on the cutting board for several minutes. So while a human heart would not maintain coordinated rhythm for long, a fibrillation-type pattern might go on for awhile.
It’s all about the ion channels. In muscle cells, the ratio of potassium, sodium, chlorine, and calcium is all very nicely regulated. An action potential (the electrochemical signal that triggers the muscle to contract) is brought about by changes in the concentrations of these ions in the intracellular and extracellular space. Sprinkling the salt messed up the delicate balance of ions and some of the channels opened, allowing them to flow in and out of the cells, which caused contractions.
And yes, a heart could have several muscle cells contracting after being removed, but they would not be coordinated beats, just fibrillation, as Jackmannii said.
Back when I worked computer support at a med school, I saw an experiment they were running in one of the labs. They were running a potassium solution through a rat heart, which was on the end of a pipet (no rat in sight). The little heart just pumped away, until they stopped the flow, at which point it croaked.
The SA node is richly innervated with vagal and sympathetic fibres. These are affected when you remove the heart from its lair. You are right that the SA and AV nodes would cause the heart to beat at intrinsic rates. This is important in denervated hearts used in transplants, which need support from chronotropes and pacemakers and have a slightly different response to exercise, etc.