0
$\begingroup$

I first thought that action potentials of His-bundle i.e. Purkinje fibers are Cardiac. However, I started to think that this is not enough. I think now that they are neuronal and cardiac. My conjecture. They have first short-acting neuronal part and then long-acting cardiac part.

Are Purkinje Action Potentials Neuronal and Cardiac?

$\endgroup$
2
$\begingroup$

The His-Purkinje fiber system is a network of one type of specialized conducting cardiac cells that carry an action potential in the heart. There are other cells which perform this function in different parts of the heart. The initiation time, shape, and duration of the action potential are distinctive for different parts of the heart, reflecting their different functions. These distinctions arise because the myocytes in each region of the heart have a characteristic set of channels and anatomy. You can completely dissociate the nervous system from the heart, and the heart will still pace itself. Think of what happens with heart transplants. This completely eliminates neuronal influence. See the following brief excerpt which explains one type of cells conduction method. Please note there is no reference to neurons.

The positive charge that enters cell A not only depolarizes cell A but also produces a flow of positive charge to cell B—intracellular current. This flow of positive charge discharges the membrane capacitance of cell B, thereby depolarizing cell B and releasing extracellular positive charges that had been associated with the membrane. The movement of this extracellular positive charge from around cell B toward the extracellular region around cell A constitutes the extracellular current. The flow of intracellular current from cell A to cell B and the flow of extracellular current from around cell B to around cell A are equal and opposite. It is the flow of this extracellular current in the heart that gives rise to an instantaneous electrical vector, which changes with time. Each point on an electrocardiogram (ECG) is the sum of the many such electrical vectors, generated by the many cells of the heart.

This has been extensively studied, so much so that cardiac electrophysiologists can pinpoint the location of a small group of cells that are misfiring by the nature of the impulse they are giving off. The annual median salary for an electrophysiologist in the US is $480,000. :-( There is a lot of grant money in this area. It's a big deal.

For in-depth study of electrophysiology of cardiac cells, please see Electrophysiology of Cardiac Cells or any other of a number of reliable sources.

$\endgroup$
  • $\begingroup$ Thank you for your answer! The case study does not cancel out my conjuncture. One reason why those neurons have not been found is that they are extremely small. They give signals of very little energy with the same frequency as Purkinje fiber. Other reason is that they are entangled to the Purkinje network together and difficult to separate them when you do not know where to look and how. It would be interesting to study the small group of cells misfiring. I am trying to get a research place in this area so I can start to research better. My options are Norway's research laboratories and USA. $\endgroup$ – Léo Léopold Hertz 준영 Nov 18 '14 at 9:58
  • 1
    $\begingroup$ @Masi - If I understand correctly, it is your contention that neuronal cells exist in cardiac muscle but they just haven't been found yet? How do you explain heart transplantation? Are there neurons that exist apart from the nervous system? $\endgroup$ – anongoodnurse Nov 18 '14 at 15:46
  • $\begingroup$ I do not know how these neuronal cells exists along cardiac muscle (in, out, near) but I have a clue that they work very closely together. And the only way to do so they should coexist, I think. I have only clues about this coexistent in Purkinje fibers. Person can live without this system some time. These neurons seem to exist in a link with the nervous system. I have not studied any heart transplantation patient. To process such an data (AAMI) similarly would tell me if similar regulation exist. It would be interesting to get such an data to understand your last case better. $\endgroup$ – Léo Léopold Hertz 준영 Nov 18 '14 at 21:27
  • 1
    $\begingroup$ Well, Hassall studied this in guinea pigs in the 80's and 90's. I found conflicting studies about it starting in the 2000's on. I don't know much about that. Clearly the nervous system has an effect on the heart. It would be interesting to study the differences in heart transplant patients vs. normal. $\endgroup$ – anongoodnurse Nov 18 '14 at 23:07
  • 1
    $\begingroup$ Thank you for your excellent comment! I sent requests of data for MIT-BIH's creator (George Moody), my close link of signal processing in Finnish Academy and my Baltic research fellows. The problem has been to get AAMI standard data. Only George's data has passed my validation at this point, although officially, many data are verified so by their AAMI devices. $\endgroup$ – Léo Léopold Hertz 준영 Nov 19 '14 at 0:15
1
$\begingroup$

On the wiki they are called cardiac action potentials. As the generation of the action potentials in the sinoatrial node is mediated by muscle cells, as is the conduction of the action potentials through the purkinje network (see wiki), the action potentials are not neural in nature, but cardiac.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.