Sarcomere length-tension relationship (video) | Khan Academy
Length-tension relationship. In skeletal muscles. Tension in muscles is composed of the forces generated by many cross-bridge formations. It is the pulling of the. The Length-tension Relationship. For muscles to contract, the muscle proteins called actin and myosin must interact with each other. This occurs when they are . The length tension relationship is the observation that isometric force exerted by a muscle depends on its length. It affects the angle of peak torque.
Pressure volume loops Video transcript So I'm going to draw up the length-tension relationship. This will be the key idea we're going to talk about in this video. And it's very related to some stuff we've already talked about.
So we've talked about, for example, the Frank-Starling curve. And that was talking about how if you stretch out heart cells, and all of the things within heart cells-- all the proteins-- that it actually changes the force of contraction.
And actually, force of contraction is very much related to this length-tension relationship as well.
So I'm going to put that up here. And instead of using that terminology, though, we're going to use the term tension. I mean, you can essentially think of them the same way. But classically, the word tension is what everyone uses. So we're going to use that same word. And then, as far as length, specifically the length that we're talking about is the length of a sarcomere.
So I'm going to write sarcomere here. And the sarcomere, just keep in mind, is really going from one z-disc to another z-disc. So to draw this out, to actually write it out maybe, we can start with myosin. And so maybe this is our myosin, right here.
And I'll draw some myosin heads here. And maybe some myosin heads on this side, as well. And, of course, you know it's going to be symmetric looking, roughly symmetric.
Sarcomere length-tension relationship
So this is our myosin. And actually, I'm going to make some copies of it now, just to make sure that I don't have to keep drawing it out for you. But something like that. And we'll move it to be just below so that you can actually see, when I draw a few of them, how they differ from one another.
So I'm going to put them, as best I can, right below one another. And we'll do a total of, let's say, five. And I think, by the time we get to the fifth one, you'll get an idea of what this overall graph will look like. So these are our five myosins. And to start out at the top, I'm going to show a very crowded situation. So this will be what happens when really nothing is spread out. It's very, very crowded. And you recall that you have actin, this box, or this half box that I'm drawing, is our actin.
And then you have two of them, right? And they have their own polarity, we said. And they kind of go like that. And so, in this first scenario, this very, very first one that I'm drawing, this is our scenario one. We have a lot of crowding issues. That's kind of the major issue, right? Because you can see that our titin, which is in green, is really not allowing any space. Or there is no space, really. And so, these ends, remember these are our z-discs right here.
This is Z and this is Z over here. Our z-discs are right up against our myosin. In fact, there's almost no space in here.
Length tension relationship | S&C Research
This is all crowded on both sides. There's no space for the myosins to actually pull the z-disc any closer. So because there's no space for them to work, they really can't work. And really, if you give them ATP and say, go to work.
They're going to turn around and say, well, we've got no work to do, because the z-disc is already here. At 1 on Graph 1, the sarcomere is overly contracted at rest. There is a high degree of overlap between the thin and thick filaments. Muscle contraction causes actin filaments to slide over one another and the ends of myosin filaments.
Further muscular contraction is halted by the butting of myosin filaments against the Z-discs.
Tension decreases due to this pause in cross-bridge cycling and formation. As the resting muscle length increases, more cross-bridges cycling occurs when muscles are stimulated to contract. The resulting tension increases.
Maximum tension is produced when sarcomeres are about 2. This is the optimal resting length for producing the maximal tension.
- Length tension relationship
- Length-tension relationship
- The Length-tension Relationship
By increasing the muscle length beyond the optimum, the actin filaments become pulled away from the myosin filaments and from each other. At 3, there is little interaction between the filaments. Very few cross-bridges can form. Less tension is produced. When the filaments are pulled too far from one another, as seen in 4, they no longer interact and cross-bridges fail to form. This principle demonstrates the length-tension relationship. Maximal tension is readily produced in the body as the central nervous system maintains resting muscle length near the optimum.
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