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A lot of stuff on this page. Maybe it should be broken up? -- Have this page talk about the native conduction system of the heart, and move the generation of action potential over to a different article (maybe action potential?). Should probably keep the control of heart rate stuff over here for now. Ksheka 13:43, Apr 22, 2004 (UTC)
I started this article a long time ago, when i was studying the pacemaker potential etc. in class. (The stuff with the funny current and that.) Artificial pacemaker used to be here, and i decided i'd make a page on how the body made these rhythmic electrical pulses naturally.
Perhaps the information about the conduction system could go in Electrical conduction in the heart or something similar. This would keep the pacemaking bit separate from the pacedelivery bit. There are a few articles where conduction could be wikified.
I thought about putting the action potential stuff on action potential, but the sections on rate control (with cAMP increasing, etc.) refer to the ion channels that create the action potential. Including control at AP would make that page too complex.
That said, i don't claim any ownership over the page; i'm easy with whatever happens. T 08:37, 23 Apr 2004 (UTC)
Create a new page, Cardiac action potential, which will describe the phase 0-4 of the cardiac action potential, and how the action potential morphology changes in different parts of the heart.
Create the second article, Electrical conduction of the heart (Maybe Electrical conduction system of the heart), that will talk about SA node, AV node, etc (The section I added to this article yesterday)
Keep this article to talk about control over the native pacemaker system (ie: sympathetic, parasympathetic, hormonal, etc.) - Basically the last section of this article.
Argh! sorry i took so long to reply! i don't have many pages on my watchlist, and i forgot about this one over my break.
I'm okay with anything that happens to the article (as long as what's happening goes in the edit summaries, and possibly talk pages, so what's happened can be tracked down).
I've forgotten most of what i knew about cardiac APs, but are the ones in the myocardium exactly the same as the ones in the pacemaker cells? I dunno, can't remember.
No. The action potentials are different in the different portions of the heart (SA node, atrium, ventricle, etc.). This should eventually be taken care of by the article cardiac action potential. I've been avoiding writting that article, because of the amount of stuff involved in the topic (over a dozen ion channels, concentrations of ions in the cell and the extracellular space, and the complex timing of the ion channels opening and closing, for a start). Ksheka 23:43, May 12, 2004 (UTC)
Before anyone mentions it, I wanted to mention that it's the electrical activation of the myocardium that causes QRS complexes, not actual contraction. That's why pulseless electrical activity is possible and it's possible to get nice-sized QRSs on an EKG in patients with very low ejection fractions. On the other hand, I'm not sure as to the mechanism of loss of P waves due to hyperkalemia -- Is it myocardial stunning of the atrial myocardium, or stunning of the electrical system in the atria? Have to check up on that... Ksheka 13:43, Apr 22, 2004 (UTC)
According to the text of the article:
Cells in the SA node will naturally discharge (create action potentials) at about 70-80 times/minute. Because the sinoatrial node is responsible for the rest of the heart's electrical activity, it is sometimes called the primary pacemaker.
According to the A&P lecture I just attended (and my textbook, not present), without innervation, the SA node will discharge about 100 times/minute, but parasympathetic stimulation lowers this to about 70 bpm
All of the heart's cells possess the ability to generate electrical impulses???[edit]
If I'm not mistaking, this is not correct. Working myocardium displays the AP curve distinctive of fast response, which has a flat phase 4, it does not have the slow diastolic depolarisation that reaches treashold of fireing on its own, but needs a stimulus. Or am I missing sth?
EerieNight16:45, 2 September 2007 (UTC)[reply]
I believe the author is trying to say that all of the heart's cells possess the ability to depolarise. It's true that only certain cell can depolarise spontaneously, due to the slowly depolarising resting membrane potential (SA node, AV node, His-Purkinje bundle). —Preceding unsigned comment added by Senaiboy (talk • contribs) 18:58, 14 November 2007 (UTC)[reply]
I may be mistaken, but it appears to me that the editor (or, more likely, several editors) are not fully consistent in the use of "cardiac pacemaker" (and "pacemaker"), sometimes referring to the whole collection of cardiac nerves and sometimes referring to the normal (or normal "lead" master) pacemaker (i.e. the SA node). Wiser heads than mine should prevail. --Jerzy•t06:55, 7 June 2016 (UTC)[reply]
An editor has identified a potential problem with the redirect Nodal tissue and has thus listed it for discussion. This discussion will occur at Wikipedia:Redirects for discussion/Log/2022 April 8#Nodal tissue until a consensus is reached, and readers of this page are welcome to contribute to the discussion. signed, Rosguill talk 15:46, 8 April 2022 (UTC)[reply]
