Talk:Muscle contraction/Archive 2

Archive 1

Archive 2

Diagram

I've asked at commons:Commons:Graphic Lab School/Images to improve#Translation German-->English for the current diagram to be translated. If you can help, please do. There are some problems with the image right now, so I'm putting it here. As it changes, keep an eye out for a point when it's ready for showtime, and stick it in there in place of the German version. Thanks! – Mike.lifeguard | ^@en.wb 14:01, 17 December 2007 (UTC)

Isokinetic

In the items:

In isotonic contraction (sometimes called "isokinetic"), the tension in the muscle remains constant despite a change in muscle length. ...

and

In isovelocity contraction, the muscle contraction velocity remains constant, while force is allowed to vary. ...

the phrase

(sometimes called "isokinetic")

seems to be misplaced; it should rather apply to the isovelocity contraction.

I did not search for references (or rather examples of usage of the word "isokinetic"), since I think this really was an unintentional misplacement. But please tell me if you want such examples. - Olaf Till (talk) 12:34, 4 January 2010 (UTC)

Muskel-molekular.png

Why is this diagram on the English page? It makes NO sense. Please remove it or add an English version. I can't emphasize enough. --128.164.100.164 (talk) 20:45, 20 April 2009 (UTC)

I second this! Adamlankford (talk) 07:42, 31 May 2010 (UTC)

I've added what I think is a decent translation, based not on a knowledge of German but on what I think's going on in the diagram. May not be correct, but more understandable than the German one, at least. In addition, where are the values for the concentrations of calcium ions cited? Also, I've not seen magnesium mentioned anywhere else but here, but that could just be me. GravityGilly (talk) 19:22, 22 June 2010 (UTC)

Flexing

I put an {{about}} message at the top of this article directing people who might be looking for the page on flexing (dance). I did this because flexing currently redirects to this article. I can not change the redirect on the flexing page to the flexing (dance) article because the original flexing article was nominated for deletion and the outcome of the AfD discussion here was to turn flexing into a redirect to muscle contraction, this article. Please leave the message at the top of the page. Thank you. //Gbern3 (talk) 15:02, 14 November 2010 (UTC)

Now I understand why you wanted that message. Made no sense at all, since "Muscle contraction" is not even vaguely near "flexing". I changed to the more appropriate {{redirect}} template. --Fama Clamosa (talk) 15:34, 14 November 2010 (UTC)

Fixed - there's no point have such an obscure and irrelevant link at the top of this page, so I just changed the Flexing page to show 3 options. Problem solved. Mokele (talk) 16:43, 14 November 2010 (UTC)

Muscle mechanics

Need to mention how muscle has series and parallel elastic elements-titin and tendons. Titin isoforms of cardiac muscle is responsible for the stiffness of this tissue compared to skeletal muscle. Regards, GetAgrippa (talk) 23:04, 16 November 2010 (UTC)

Over the river and through the woods?

Our article's opening sentence currently reads: Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. I recognize this isn't a simple topic, but "actin and myosin cross-bridge cycling"? Really? I have no doubt that this is a correct explanation, but it leaves me none the wiser. Perhaps this image concisely illustrates this phenomenon called "cross-bridge cycling"?

Nor is it possible for the biology-naive among us to easily discover what might actually be meant by "cross-bridge cycling" via a Wikipedia search. Is there any help for it? Reading a first sentence that tells the uninitiated reader absolutely nothing ( without she immediately leaves the page to educate herself elsewhere for the next 30 - 60 minutes ) really is quite offputting. I'm very comfortable in other sciences, btw: I'm not asking for an article or an opening sentence that will satisfy people who are just allergic to science in its entirety. ;-) But something that's at least somewhat accessible to a typical college student who hasn't made biology the focus of her study would be very pleasant.  – OhioStandard (talk) 15:04, 23 October 2011 (UTC)

Yeah, I've been meaning to re-work the article for a while, but have been buried in RL work. I do agree it should be much simpler, though - I detest articles like many of the math articles which are incomprehensible to anyone without a PhD in the subject. Problem is, "cross-bridge cycling" is actually part of my day-to-day vocabulary, so I'm a bit blind to what's an appropriate level for most people. Is it just a few bits in the intro that need fixing, or does the whole thing need to be re-worked? Mokele (talk) 15:48, 23 October 2011 (UTC)

I appreciate this very gracious reply, and will just mention, in passing, that it amuses me that I'm all to seek in this topic area ( although I'm probably at the higher end of familiarity with neuroanatomy and neurophysiology, for a layman ) but love many of our very specialized articles on topics in mathematical philosophy, which most of our readers probably find tolerably opaque and inaccessible.

Long body of comments collapsed here, by their author, to conserve real-estate.

This article is clearly rich in content, very dense, in the best sense of that word. I'd hate to see any of that very satisfying depth and quality lost, for the sake of improving accessibility. So my personal preference would probably be to just simplify the lead, a bit, and especially to try to put up an opening sentence that can be digested by, say, a fairly bright 17-year-old with no previous instruction in the life sciences. For example, I noted the sentence "The interaction of sliding actin and myosin filaments is similar in ..." elsewhere in the article, which gave me some clues to what's going on, but it's not even remotely clear ( to the uninitiated ) from followingthe wikilinks to Actin and Myosin in the opening sentence that we're talking about filaments ... or ( as I suppose, possibly incorrectly? ) about the building blocks or constituents of two different kinds of filaments or strands arranged in particular ( helical? ) three-space/physical configurations relative to each other that vary over time to produce, e.g. limb movement. After spending 30 minutes trying to puzzle through the text of the article, I finally clicked on its initial diagram and stared at it in high-res mode for a while. I soon wished I'd done that initially, before trying to make sense of the text. From a neophyte's perspective, I see that diagram as an asolutely essential point of departure: It allows one to begin with something for which we all have some approximately-correct intuitve understanding, viz. that muscles are made up of more or less parallel strands. That comfortable "macro"/"gross" level notion is one that's easy to accept based just on our own sensory experience of our own skeletal muscles. Taking that "gross" level concept as a departure point, and "zooming progressively in", conceptually speaking, toward the "micro" level structures, and their supporting mechanisms, processes, biophysics/dynamics, and physiology seems to me the most promising approach. Does that seem sound to you, pedantically? Btw, should "motor unit" be wikilinked on it's first occurrence, at least? Just a suggestion: I'm so very far out of my depth here that I'm not going to try to edit it even in small ways that seem innocuous... If that diagram were made into an animation, now: Well, that would be the most promising approach one could hope for, I suppose. It would be a monumental undertaking, though, to produce a "How a muscle functions" movie, though. Have any undergrads lurking about who might be looking for 499 credit, and who know how to produce animations? ;-)

Thanks very sincerely for hearing my hopefully-constructive criticism so well, for being willing to engage that way. I don't expect any content-related explanations or tutoring, btw. My parenthetical questions were rhetorical, just sort of thinking out loud, so to speak, Best,  – OhioStandard (talk) 19:22, 23 October 2011 (UTC)

Well, really I guess you could say that tension is achieved by filaments of two proteins (actin and myosin) sliding past each other. "Cross bridge cycling" is the whole term for the molecular mechanism for exactly how this is achieved (and there's an attempt to explain this later on in the article), but it's hardly introductory, as you say.

Potential for an opening sentence somewhere in that comment? GravityGilly (talk) 23:39, 17 November 2011 (UTC)

The crossbridge is the interaction of the globular myosin heads with the active sites of actin. The crossbridge can be cycling generating force, can be dephosphorylated myosin heads (such as smooth muscle)that are slowly cycling and maintain the latch state in mammalian smooth muscle, or can be fixed as in rigor mortis. There are elastic elements in series in the myosin arms, and titin which connects myosin to Z line, and parallel elastic elements within the connective tissue or tendon. The elastic elements are often under estimated in their contribution to muscle mechanics such as isoforms of titins in skeletal muscle and cardiac muscle. You can discuss how the myosin globular heads are cocked and then hydrolyze ATP to generate force. Oops forgot to sign. Regards GetAgrippa (talk) 00:23, 18 November 2011 (UTC)

Force resisting eccentric motion

I'm reverting the edit just done by HCA, who commnented, "Correcting mistaken deletion - in order for a muscle to lengthen, the force MUST be greater than peak isometric force." This is not true. In order for the muscle to lengthen at a constant rate, it suffices that the force applied to the muscle be just as strong as the force that the muscle exerts. That gives a balance of forces, and therefore zero acceleration (zero change in speed of muscle lengthening). In order to initiate muscle lengthening, the applied external force must be a bit greater than the force exerted by the muscle. When the speed of muscle lengthening decreases, it is because the muscle exerts more force than the applied force. This is simple Newtonian physics. Eric Kvaalen (talk) 15:41, 17 December 2012 (UTC)

Unfortunately, this fails to take into account one of the two most fundamental properties of muscle - the force-velocity curve. A muscle subjected to a load less than its peak force will *not* accelerate, as you would think from physics 101. This is because increased muscle speed reduces the number of cross-bridges in attachment at any given time, as a function of the actin binding and releasing affinity of the myosin molecule, and thus the number of force-generating elements declines. Thus, a constant load will be raised/moved by a muscle at a constant speed, because if the speed increases the force will instantly decline and vice versa, leading to a stable state. Furthermore, the same load will be raised at different speeds by fast and slow fiber muscles, even though the isometric force is (mostly) the same - what determines the speed is myosin binding rates, in which the two fibers differ. The same is true for eccentric contractions - the muscle's rate of lengthening is determined by the force and myosin binding rates. However, this is only true over a highly limited range of speeds, beyond which the point becomes moot due to damage to the muscle that significantly impedes function. Now, muscle behavior under loads in "real world" conditions (accelerating limb and body masses, moving fins through water, etc.) can depart from this, but the FV relationship still dominates. But still, if at any point the load on the muscle declines below maximum isometric strength, the muscle *will* begin to shorten. (Obviously I'm leaving out complexities like tendons, pennation angle, dynamic gearing, etc.)

Short version - because muscle contraction is just a very, very big set of chemical reactions, the chemistry determines the speed. When overall muscle speed increases or decreases, the actual number of myosin "motors" being used changes, leading to a change in force output entirely independently of F=ma. HCA (talk) 19:12, 17 December 2012 (UTC)

Could any of these images replace those on the page

commons:Category:CNX I've uploaded some free images from CNX.org , and some of these could do well on this page. CFCF (talk) 13:22, 5 December 2013 (UTC)

(a) The active site on actin is exposed as calcium binds to troponin. (b) The myosin head is attracted to actin, and myosin binds actin at its actin-binding site, forming the cross-bridge. (c) During the power stroke, the phosphate generated in the previous contraction cycle is released. This results in the myosin head pivoting toward the center of the sarcomere, after which the attached ADP and phosphate group are released. (d) A new molecule of ATP attaches to the myosin head, causing the cross-bridge to detach. (e) The myosin head hydrolyzes ATP to ADP and phosphate, which returns the myosin to the cocked position.

Possibly the one here to the right. CFCF (talk) 13:24, 5 December 2013 (UTC)

Waste products?

I have been told that muscle contraction causes an accumulation of waste products like carbon dioxide, and that blood flow is not always sufficient to transport waste products away from the muscle that is contracting. The excess carbon dioxide will eventually prevent the muscle from contracting until the blood carries the waste products away. Is this true? Are there any other waste products beside carbon dioxide? The main page of this article would be improved if a paragraph were added explaining why waste products accumulate in muscles that are subjected to exercise. Dexter Nextnumber (talk) 20:42, 15 May 2010 (UTC)

Dexter Nextnumber- That would be more applicable to a discussion of cellular respiration. 76.206.9.22 (talk) 03:43, 1 May 2014 (UTC)

Content stolen from a website?

The "Force-length and force-velocity relationships" section looks suspiciously similar to https://www.boundless.com/physiology/textbooks/boundless-anatomy-and-physiology-textbook/muscle-tissue-9/control-of-muscle-tension-97/force-of-muscle-contraction-542-9172/

Has it been copied without permission?

Wootery (talk) 05:08, 27 March 2015 (UTC)

Wootery No, boundless use our articles in their books. They copy us, and also attribute us. -- CFCF 🍌 (email) 10:08, 27 March 2015 (UTC)

Excitation - contraction coupling

I would recommend keeping this topic as a separate article, as it may get "lost" in a very long article like "muscle contraction."```` — Preceding unsigned comment added by 65.185.127.203 (talk) 20:29, 3 September 2014 (UTC)

I agree. danielkueh (talk) 23:49, 1 June 2015 (UTC) I disagree. We can't talk about one without the other. It makes no sense to have so much duplicacy in two separate articles.

Merge Sliding filament model into Muscle contraction

It appears like the article on the Sliding filament model is essentially a duplicate of what is already given in Muscle contraction. The Sliding filament model is simply a method of describing it, but it seems redundant to have an own article to describe the description of muscle contraction. Mikael Häggström (talk) 07:46, 6 February 2011 (UTC)

I'm ambivalent. On one hand, they definitely deal with the same same function. On the other, keeping them split keeps the page from being too long, an allow there to be one page for molecular mechanics and another for whole-muscle contraction stuff (twitch vs tetanus, force-velocity, etc.). More generally, I'm painfully aware of how badly all the muscle articles overlap with large gaps, and it all needs a major overhaul. I'm also tempted to keep it as is because the whole story of how the sliding filament theory came to be is pretty cool, but would just clutter up the muscle contraction page.

By the way, thanks for the edit work you've been doing lately on muscles. If I could make a request, smooth muscle contraction mechanics is something we're sorely lacking, and I know very little about it. If there's anything you can add, it would be greatly appreciated. Mokele (talk) 23:56, 6 February 2011 (UTC)

This article is very similar to Excitation-contraction_coupling also. CR13/12/11 — Preceding unsigned comment added by 83.71.72.136 (talk) 18:57, 13 December 2011 (UTC)

Support I support the merge and also propose that Excitation–contraction coupling too be merged into this article. Diptanshu^Talk 12:43, 29 November 2013 (UTC)

Support I support these merges and would be very grateful if Mikael Häggström, who seems to have put a lot of effort into this topic, would help complete the merge (am afraid I will miscommunicate something if I perform it myself)--LT910001 (talk) 11:09, 23 December 2013 (UTC)

 Done - I've performed the merge now. I found very little referenced non-duplicates in the Sliding filament model article, but if anyone finds more text worth of moving from that article then feel free to supplement. Mikael Häggström (talk) 14:46, 26 December 2013 (UTC)

Thanks Mikael Häggström. --LT910001 (talk) 00:40, 27 December 2013 (UTC)

I think it might make sense to merge Excitation–contraction coupling into muscle contraction, as the term is only used in relation to voltage and muscle cells, as far as I know. But it might also make sense to re-create the sliding filament model to fill in the molecular biology details, as there's some evidence there's a very similar calcium-modulated roles for motor proteins and filaments in e.g. eggs, developmental biology, and even Arabidopsis (see how many non-muscle roles Myosin has for instance: https://en.wikipedia.org/wiki/Myosin) Mirams (talk) 09:39, 13 August 2014 (UTC)

Support. Like everyone else above. I support the merger of excitation-contraction coupling and muscle contraction. danielkueh (talk) 03:59, 2 June 2015 (UTC)

 Done - I completed the merger of muscle contraction and excitation-contraction coupling. danielkueh (talk) 03:59, 2 June 2015 (UTC)