Three Hearts... Beat As One(?)

Discussion in 'Physiology and Biology' started by monty, Apr 14, 2010.

  1. monty

    monty Colossal Squid Staff Member Supporter

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    I was telling a friend about cephs having three hearts, and she asked if they are synchronized with one another... I had to admit, I have no idea. Does anyone know how the beating of the three hearts is timed?
     
  2. CaptFish

    CaptFish Colossal Squid Staff Member Moderator

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    Just my thought but I always figured the two hearts that pump blood across the gills work together at the same pace while the third which circulates the blood through the body works on its own at its own pace.
    But I have no idea this is just how I pictures it.
    Very Good question!
     
  3. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Following CaptFish's thoughts with my own unscientific observations, I have never seen the gills work independently but our heart and lungs are not particularly synchronized that I know of so there may be no value to the observation to suggest an answer. When Sisturus died, I had the impression that one gill heart has stopped because he lost functionality on one side. The inability to control that side might suggest some kind of synchronization to keep equilibrium but the paralysis could easily have been just the loss of blood flow.
     
  4. tonmo

    tonmo Titanites Staff Member Webmaster Moderator

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    Re: Three Hearts... Beat As One(?)

    Having just been through an EKG and echocardiogram, it would be quite interesting to have a dr. (with ceph expertise) do this to an octopus - one for each heart, and compare the results. Getting the sensors on the ceph and keeping it there would be a challenge for sure!
     
  5. cephalopodcast

    cephalopodcast O. bimaculoides Registered

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    http://bit.ly/918KHh

    Also, http://scholar.google.com/scholar?q=cephalopod+circulation&hl=en&btnG=Search&as_sdt=40001&as_sdtp=on
     
  6. Level_Head

    Level_Head Vampyroteuthis Registered

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    Apparently the heartbeats are related, but independent, according to this:
    Looking around, it seems that some drugs affect the systemic heart more than the brachial hearts, and vice versa. The systemic heartbeat -- about once every three to eight seconds according to the above -- seems surprisingly slow to me.
     
  7. Level_Head

    Level_Head Vampyroteuthis Registered

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    Nervous control of the heartbeat in Octopus (1979)

    This paper suggests that the systemic and brachial heartbeats are the same rate, but that the brachial hearts are off by two thirds of a cycle from the main heart.

    Now, this is done under experimental conditions in which they are cutting nerves to the hearts (ugh), but one of the figures is a multi-cardiogram, which matches the description in the text.
    http://jeb.biologists.org/cgi/reprint/85/1/111

    It isn't clear if they can operate with different rates in intact animals--the rates are affected by exercise/stress and oxygen level. In their experimental trace shown, the trio were beating at a pulse rate of about 45 (7.5 beats in ten seconds). This was described as similar to the resting rate of intact animals, and is rather faster than described by the paper in the previous comment.

    Interestingly, the pulse rate is in the range of humans; slower than my resting rate, but faster than my little brother's. The test animals seemed to average about that, with there range shown of 37 to 55 resting rate.

    Blood pressure was lower than human, though of course much higher than any non-cephalopod mollusk (which are open circulations, unless cephalopods and vertebrates). The blood pressure seemed to average about 40 over 20, with a high of 50/30 and a low of 25/15. (The measurements of pressure are in cm of water.)

    The hearts still beat in the same synchonized pattern with the nerves cut, and the trio of hearts still increased with temperature and oxygen (more oxygen, faster heartbeats).

    They cut different nerves--from the brain, and from the body--and even injected drugs into one brachial heart to see if the other side would react to it (it did, almost instantly, keeping in synch). It's interesting, and talks about the animals' ability to stop their hearts for seconds at a time when startled. (A prior paper reported this as "minutes" for O. dolfleini.)

    They note that slicing a creature open and pinning his mantle back interferes with his heartbeat. I can certainly sympathize.

    As an aside, I have held people together who were sliced open, and I'm a pretty good jackleg first aid person, but I find myself wincing at descriptions of these experiments. Many of you have kept octopuses for years, and grow understandably attached to them—for me, it's been decades since I had one, but I've spent so much time writing novels about fictional octopuses that the attachment is just as strong.

    I'm glad that the anesthetic is required these days, at least.
     
  8. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    The hearts still beat in the same synchonized pattern with the nerves cut, and the trio of hearts still increased with temperature and oxygen (more oxygen, faster heartbeats).

    This seems odd. Why would the heart work harder in higher oxygen? I keep thinking oxygen levels may be more important (especially in the hatchlings). I am not sure how it actually plays out but this seems counter to what I would think.
     
  9. Level_Head

    Level_Head Vampyroteuthis Registered

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    It is counterintuitive to me, as well. It caused me to look carefully at these sections:
    Can you see any other way of interpreting the described response to oxygen? I'm with you—circulation slowing down when the animal needs more oxygen than the seawater is providing doesn't make intuitive sense to me.

    One possibility is a sort of secondary feedback; the increased pumping of water through the mantle would increase its oxygen content (since some would be removed by the gills), causing a speedup of heartbeat. But that doesn't make a lot of sense.

    The other end of the scale does, a little bit: if the mantle's not pumping (if, say, the animal has frozen to avoid detection), there is not much sense to circulation. Still, the octopus's heart stops abruptly when startled, far faster than this feedback mechanism could accomplish—suggesting that it isn't necessary or used for that.

    At least the heartbeats pick up when octopuses are alarmed. I was glad to see that; it saved me from some rewriting.
     
  10. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    Non-scientific conjecture has me wondering if there is a secondary way to abosorb oxygen that stops if there is oxygen rich water. Something of this nature would help explain the odd observations for the activity of humboldt squid in the low oxygen zones (a mystery that Dr. Gilly is currently trying to unravel).
     
  11. Level_Head

    Level_Head Vampyroteuthis Registered

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    Well, we know that at least some octopus species can aborb water ... ah, backwards. Some land mollusks breathe through their skin--and some have arrangements rather like land-vertebrate lungs. I've seen some reference to octopus skin absorption, but I cannot now recall if it was water or oxygen, and it's not in my notes.
     
  12. ceph

    ceph Wonderpus Staff Member Moderator

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    >Why would the heart work harder in higher oxygen?

    My best guess:

    I think the better question is why would it work slower in lower oxygen. When I hold my breath and swim under water, or when I scuba dive, I can get much farther and stay down longer if I'm relaxed. If I'm excited or trying to swim fast, my heart is going faster, my metabolic demands will be much higher. I may be more active but am using my air much less efficiently. I suspect the animal is regulating its activity levels to match the oxygen levels. An increase of the heart would increase demand for oxygen when there is less to be had - this could become a negative feedback loop. Thats my guess. Brad Seibel would know, my physiological work focuses on growth rates, not circulation.

    There is some level of gas exchange through their skin.

    Temperature is an easier one as it effects the rate of the chemistry of life. Colder temps slow metabolism down for cephs.
     
  13. Level_Head

    Level_Head Vampyroteuthis Registered

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    It seems to me that whole-body and heart exercise are not the same thing. When you're swimming hard, your respiration and circulation have to work harder to get oxygen to the demanding tissues. When you're at rest, the "normal" rate applies.

    But if you're at rest, and the room's oxygen drops, your breathing speeds up--you have to work harder to extract and deliver the "resting level" oxygen to the tissues. The symptom "shortness of breath" is associated with low oxygen levels. (Heartbeat can be slowed, though, as 19% of patients in a study experienced slow heartbeat when their blood oxygen level fell for a couple of minutes.)

    I'd agree that it makes sense to slow down the overall metabolism in low oxygen conditions. But the respiration process seems that it would be separate.

    Some folks here have noticed octopuses in low-oxygen water seeming to gasp or breathe heavily, but who returned to a more normal behavior when the oxygen content of the water was increased.

    Perhaps the mantle respiration increases, and the hearts beat more slowly, at the same time. The study linked above shows that they are at least not linearly coordinated.

    What do you think? Have you seen the low-oxygen/fast-breathing effect?
     
  14. CaptFish

    CaptFish Colossal Squid Staff Member Moderator

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    From my experience you will yawn a lot then just fall asleep. That's what happened to me.
     
  15. Level_Head

    Level_Head Vampyroteuthis Registered

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    You're taking the other side? O2, Bruté?

    What about that famous song that describes what happens to a person in a low-oxygen environment? He "pants on the ground."

    Looking around on this topic, it seems that there are significant differences between hypoxia (low oxygen) and hypercapnia (high CO2). The resulting differences in respiration rate--the Type I and Type II respiration failures, are described in this Wikipedia article which talks about diving, too. The article is not well-sourced.
     
  16. CaptFish

    CaptFish Colossal Squid Staff Member Moderator

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    I'm not on any side.

    Never heard that song. it must not be that famous

    I dont know if I experienced hypoxia or hypercapnia. I never thought about it until now. It was an occasion were I was the passenger in a small plane. we were flying in the mountains. the pilot was wearing a O2 mask and I was not. At one point we were high enough that I basically just fell a sleep, then when the plane went lower I woke back up. Nice little nap. I think that it was Hypoxia.
     
  17. Level_Head

    Level_Head Vampyroteuthis Registered

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    It sounds like it. I am reminded of the Helios Airways flight 522, for which a memorial service was held in the last day or so. The crew did not recognize that they had forgotten to pressurize the aircraft (and even silenced the alarm); all were impaired and the aircraft ultimately crashed, killing all on board.

    Heartbeats are hard to tell from observation, but the mantle activity seems readily observable. Have you observed a "distressed breathing" response in octopuses or squid that you associated with low oxygen levels?
     
  18. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    We have seen excessive breathing that was eliminated when the water was areated. This is most likely to be high CO2 but also low O2. I am not sure I fully grasp the difference when I think about it though. In the case of low O2, something would be displacing it in the water, if not CO2 then nitrogen or other gases as I don't think (but don't know) the gas levels would just get thin like being higher in the atmosphere.
     
  19. Cephalover

    Cephalover Pygmy Octopus Registered

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    As far as the hearts slowing down in response to less oxygen in the water, it might be that a common mechanism both slows the heart and reduces general muscle activity/behavior in response to hypoxia. This could be adaptive because it would keep the animal from over-exerting itself and running out of oxygen in these conditions, and the heart slowing could either directly limit muscle contraction (and thus oxygen use) or these two things could be limited by some common third mechanism. I have no idea how one would go about proving this. I think this may have already been said.

    Also, respiration rate and heart rate might not be directly coupled in octopus. It seems sensible to me that in low-oxygen conditions, the respiration rate speeds up to get more oxygen flowing across the gills, and the heart rate slows down so that each unit of hemocyanin has more time to pick up oxygen while it's in the lungs.

    Now I wish I knew more about cardiac physiology.
     

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