Length-tension relationship :: Sliding filament theory
what happens to sarcomeres during contraction. It shortens This is called the length-tension relationship. Myosin thick or occurs as the muscle tension diminishes and the muscle lengthens What is the ideal length of a sarcomere. length. The relation between sarcomere length (in microns) and active It is important that you realize that skeletal muscle in your body, when at resting length, is at its optimal length The inflection occurs at almost exactly m m!. The ideal length of a sarcomere to produce maximal tension occurs at 80 A graph shows the relation between tension and time during muscle twitches.
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.
Sarcomere length-tension relationship (video) | Khan Academy
And maybe some myosin heads on this side, as well. And, of course, you know it's going to be symmetric looking, roughly symmetric. 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.
Length tension relationship
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. 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. So in terms of force of contraction for this scenario one, I would say, you're going to get almost no contraction.
So when the length is very low, so let's say this is low. Maybe low is not a good word for length. Let's say this is, I'll use the word short. The sarcomere is short. And here the sarcomere is long. So when it's short, meaning this distance is actually very short, then we would say the amount of tension is going to be actually zero. Because you really can't get any tension started unless you have a little bit of space between the z-disc and the myosin.
So now in scenario two, let's say this is scenario two. And this is my one circle over here. In scenario two, what happens? Well, here you have a little bit more space, right? The heart has an intrinsic control over the stroke volume of the heart and can alter the force of blood ejection.
Force-velocity relationship Cardiac muscle has to pump blood out from the heart to be distributed to the rest of the body. It has 2 important properties that enable it to function as such: It carries a preload, composed of its initial sarcomere length and end-diastolic volume. This occurs before ejecting blood during systole.
This is consistent with Starling's law which states that: Force-velocity relationship in cardiac muscles. At rest, the greater the degree of initial muscle stretch, the greater the preload. This increases the tension that will be developed by the cardiac muscle and the velocity of muscular contraction at a given afterload will increase.
Upon stimulation of cardiac muscle, it develops isometric tension without shortening. Once enough tension has accumulated, the muscle can now overcome the afterload and eject the blood it was carrying. Tension however is maintained at this stage. Tension is greater in muscle stretched more initially as the preload at a given velocity for muscular shortening.
The same muscle with a shorter resting length has a lower tension in comparison. These observations are consistent with the length-tension relationship.
At the hypothetical maximum velocity of shortening marked Vmax on Graph 3muscular shortening is consistent and contracts at the fastest rate when there is no afterload. Intensity of eccentric exercise, shift of optimum angle, and the magnitude of repeated-bout effect.
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