Let’s imagine that organs can be perfectly grown in a lab and installed into a body without any chance of rejection or other complications usually associated with organ transplant.
You, a perfectly healthy adult human, go to the doctor and have them put a second heart in your chest that is connected to the circulatory system with your original heart.
What would be the effects of this? Could it even be done in this hypothetical situation at all?
It’s better, which is why we already do.
Mammals have a double circulatory system, with the left and right ventricles effectively acting as separate hearts that happen to be physically connected.
Citation needed. The junctions in cardiac cells make electrical signals propagate through them all, so acting independently isn’t something that’s normal. There’s two loops, but one pump. It’s a single system.
Even if they were physically separated you’d want them to pump in sync, to maximize the pressure. So having them share electrical signals is just the optimal setup for two hearts.
you want to maximize flow, not pressure. maximizing pressure is a great way to die of stroke.
Not absolute pressure, but pressure per unit of work (i.e., efficiency).
You’re being needlessly pedantic
The reality is that they’re two hearts
If they were to be carefully separated, but with the SA & AV nodes still connected somehow (ignoring the fact that the Perkinje fibres and bundle of hiss can also act as pacemakers), you’d have two separate hearts doing their thing
Well they’re not separated, so who’s really making the pedantic argument here?
But if the nodes are connected, it’s still a single pump.
You’re merely choosing to redefine the terms. The nodes are part of the heart as a system - remove the nodes and well, the pump no longer pumps.
Your argument is like saying you can split a multi-cylinder automotive engine in half, leave the ignition system in place, and you have 2 engines.
No, you have one engine split in two, with it’s electrical timing system still determining how each cylinder maintains the exact same timing as before.
(Automotive engines are essentially air pumps with very specific timining mechanisms, as each cylinder’s output affects other cylinders, akin to the timing in a heart).
You’d also have to solve the problems of them working with each other instead of against each other.
What happens to your blood pressure? Do they beat at the same time then how do you mitigate the pressure spike. You now have twice the capacity your blood vessels are meant to handle.
If they don’t beat at the same time how do you make sure blood does not just go back and forth between the hearts, but actually does something useful?
If they’re in series the pressure will increase, if they’re in parallel the flow would increase. Just have a pacemaker organ connected to both to time the pumps. You could reduce blood pressure but increase the amount of blood flowing, therefore less wear and tear on the hearts, arteries, organs, etc.
Not a hole Keisha. A VALVE.
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i was gonna say, there have been a couple times my vision got grey and i thought i was going to pass out, but i just pumped my legs for 10 seconds and i was fine.
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Adequately pressurized doesnt seem like a problem here, over pressurization does seem like an issue, the body is very good at self regulation.
If you had 2 hearts, i can imagine each heart only needing to work half as hard to keep a person alive, except for times when the blood vessels themselves become “unnaturally” over pressurized, such as the case of regularly high blood pressure, then both hearts have to work harder, regardless of how many hearts you have.
I dont theoretically see an issue with 2 hearts
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Desychronization will likely happen considering the heart rate is varying. Both must somehow increase by exactly the same rate. Any slight variation will cause them to go out of sync.
Once they’re out of sync, it’s going to be hard for them to get back in sync.
This is assuming both hearts are independent systems. Could be a different story if there dependent (like connected in series rather than parallel), but in that case it’s conceptually no different than having one heart.
We already have synch issues with a single heart (things like arrythmias). I’m not sure two hearts in a mammal would even work, given the increase in distance for signaling - seems a lot of opportunity for error.
The heart is a really simple contraption. The heart is broken down into 2 halves, and 2 more halves after that, for a total of 4 parts.
Focusing on one half, what most people would recognize as “the heart” and what it does. Blood enters the heart into a mini pump, that pump pushes blood into a second pump, making it a little extra full, so when that pump decides to squeeze, you get extra force leaving it to send blood to the rest of the body and back to the other half of the heart later.
Imagine filling a water balloon with half way some water and squeezing it out. It doesnt have as much “umph” as if you filled that same water balloon nearly to its popping point and squeezing.
The other half of the heart is the exact same, just weaker as it only sends blood a short distance to your lungs and back to the big half of the heart. Thats it, thats all the heart does. 2 pumps that load up the other 2 pumps with blood to be shot out to the rest of the body.
Sometimes things go wrong, youve very likely felt a small heart spasm before, but the heart is a mostly self correcting, fully autonomous system. I cannot see why adding in a 2nd heart would be a detriment, just makes blood go round and round more often.
I spent a few years studying as an EMT and Medical Assistant and I think I loved the circulatory system the most. However, Im no doctor and I simplified the heart a bit because I dont think needing to understand everything adds to the theoretical discussion of 2 hearts
My concern would be complexity.
More points to fail, and I’m not sure that it reduces single-points of failure much.
I understand the concern, but I see it as more redundancy, like kidneys. If 1 heart gives out, you have a spare, and considering that we only have 1 that can do its job for 100+ years i dont see complexity as being an issue.
Also Im just here to advocate the theoretical that you could have 2 hearts with no issues, rather than it being something completely impossible.
The problem comes in, what happens when a heart fails? depending on the failure mode, it may represent a total blockage, in which case you’re toast. You might be able to survive with one heart if you had two, but if you add a second heart, then your other heart will likely be less developed unable to perform at whatever peak performance you had before.
If your method of redundancy adds more single points of failures. Also, the addition of a second heart poses the problem of keeping them coordinated; with all sorts of problems coming up if they get out of sync. adding redundancy will always add complexity, especially as you work to remove single points of failure and try not to add extra. In some systems, it’s just unwise to add redundency because the complexity means it’s more likely to fail.
Famously, Charles Lindbergh, for example, opted for a single reliable engine over two engines. It kinda flew in the face at the time. But then he was the first to go from NY to Paris in a non stop flight, in the Spirit of St Louis. Similarly, we can expect, if there was in fact some significant advantage, that then, everybody would be doing it. Or, at least, lots.
Keep in mind, cephalopods have 3 hearts- 2 are single chamgered things that boost blood over gills, and the 3rd provides bloodflow to the rest of the body. Hagfish have one chambered heart and several boster things that aren’t really much of a heart. Earthworms aren’t possessed of true hearts (they lack chambers and valves,) cochroaches and leaches also don’t have true hearts.
But where we see 4 chambered hearts (birds, mammals, and crocodillian reptiles,) they all only have 1. That should tell you something.
I agree with what youre saying completely, Im just saying i theoretically could see how you could live with 2 hearts, not the efficiencies, intricacies, or failures of having 2.
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Worse if you’re not a Time Lord or an octopus (or other multi hearted animal). They’d probably beat out of sync and cause turbulence in blood flow, which is quite bad.
Perfectly healthy? Probably the only real advantage is redundancy, but that comes at the cost of complexity, and on balance, I’d guess that it’s a net negative.
Mostly because I can’t think of any organism that normally has 2 hearts. If there were real advantages, it seems, I dunno. Inevitable?
Pretty sure giraffes have 2 hearts, I think the brachiosaurus also had 2 hearts too. I have a feeling there was a fish or other ocean creature with multiple hearts and maybe another mammal?
Heres some info I found real quick. No giraffe, several sea creatures, a couple land animals, one dino maybe, and some vague ambiguity.
Giraffes are mammals and only have 1 heart. It’s freaking huge, though, at 11 kilos.
octopus and cuddlefish and similar frequently have multiple “hearts” but they’re not the same as mammalian hearts. Briachiosaurus probably had an even larger heart than a giraffe, but it was still a singular, 4 chambered hear.
As others have pointed out the issues, I will answer a different question.
It would be cool to have a backup heart. It sits unused and quite until needed. Clearly some issues with experiencing the same conditions as the first heart. If it were biological, then it would weaken without use.
But a small pump to survive a heart attack would be nice.
NAD.
Having said that, if your “primary” heart is having issues it’s usually something that a second heart wouldn’t be able to bypass.
For example, if the heart chambers are just fluttering then your second heart could try to take over, but I imagine that if the primary failing one would cause so much ruckus that the secondary wouldn’t be able to keep up normal blood flow.
I imagine a better system with some electronics that can either work as a pacemaker or take over completely in an emergency situation by just plain stopping the heart and taking over until help arrives, or something like that.
Again, NAD
I dont think it will be beneficial. It w would probably cause hypertension. And it’s not like bodies have a lot of extra space now where you can fit a heart, so you’d be suppressing other organs.
Without your body evolving to require it? It would be worse.
The proverbial “two hearts in one chest” indicate a split mind, and create much pain.
It won’t do no good. The two would work against each other.
Not only in the holistic meaning, also from a strictly materialistical / technical point of view, there is no way to make them work synchronized. It is the very nature of the heart to determine it’s own rhythm.
And even a singular heart can have some weirdness when it’s own timing signals find alternate paths, like in some arrythmias.
I can only imagine the chaos of trying to keep signals synchronized between two hearts.
