Types of Forces
Find out why the length of a sarcomere (in diastole) affects the amount of force that it can. The tension force is the force that is transmitted through a string, rope, cable . Complete the following table showing the relationship between mass and weight. The isometric length-tension curve represents the force a muscle is The force- velocity relationship, like the length-tension relationship, is a.
So let's draw that. Let's draw a little bit more space. Let's say you've got something like that.
What is tension?
And I'm going to draw the other actin on this side, kind of equally long, of course. I didn't draw that correctly. Because if it's sliding out, you're going to have an extra bit of actin, right? And it comes up and over like that. So this is kind of what the actin would look like. And, of course, I want to make sure I draw my titin. Titin is kind of helpful, because it helps demonstrate that there's now a little bit of space there where there wasn't any before.
And so now there is some space between the z-disc and this myosin right here. So there is some space between these myosins and the z-discs. In fact, I can draw arrows all the way around.
And so there is a little bit of work to be done. But I still wouldn't say that it's maximal force. Because look, you still have some overlap issues.
Remember, these myosins, right here, they're not able to work. And neither are these, because of this blockage that's happening here. Because of the fact that, of course, actin has a certain polarity. So they're getting blocked. They can't do their work. And so even though you get some force of contraction, it wouldn't be maximal.
So I'll put something like this. This will be our second spot. This will be number two. Now in number three, things are going to get much better. So you'll see very quickly now you have a much more spread out situation. Where now these are actually-- these actins are really not going to be in the way of each other. You can see they're not bumping into each other, they're not in the way of each other at all.
And so all of the myosins can get to work. So the z-discs are now out here. My overall sarcomere, of course, as I said, was from z-disc to z-disc. So my sarcomere is getting longer.
And you can also see that because now there's more titin, right? And there isn't actually more titin. I shouldn't use that phrase. But the titin is stretched out. So here, more work is going to get done.
Length tension relationship | S&C Research
And now my force, I would say, is maximal. So I've got lots, and lots of force finally. And so it would be something like this.
And so based on my curve, I've also demonstrated another point, which is that, the first issue, getting us from point one to point two, really helped a lot. I mean, that was the big, big deal. Because you needed some space here.
Again, this space really was necessary to do work at all. And now that we've gotten rid of the overlap issue, now that we've gotten these last few myosins working, we have even more gain. But the gain was really-- the biggest advantage was in that first step. Now as we go on, let's go to step four. So this is step four now. As we go here, you're going to basically see that this is going to continue to work really well.
Because you have your actin, like that, and all of your myosins are still involved in making sure that they can squeeze. So all the myosins are working. And our titin is just a little bit more stretched out than it was before. And our force of contraction is going to be maximal. And you're going to have-- and so here, I'm drawing the z-discs again.
Muscle Physiology - Functional Properties
They're very spread out. Our sarcomere is getting longer and longer. And our force of contraction is the same. Now let's just take a pause there and say, why is it the same? Why did it not go up? Well, it's because here, in stage three, you had 20 myosin heads working.
Up here, you had something like 16 out of 20 working.
Here, we said maybe zero out of 20 right? And here, you again have 20 out of So you still have an advantage in terms of all of the myosins working. But there's no difference between 0.
Because again, all the myosins are working. So now in stage five, we kind of take this a little too far, right? So let me actually just make a little bit of space here. We take this a little bit too far in the sense that our actin is going to slip out all the way over here. And it's going to be out all the way over here. So we've got a huge, huge gap now. When tension at each length is plotted against length, a relationship such as that shown below is obtained.
While a general description of this relationship was established early in the history of biologic science, the precise structural basis for the length-tension relationship in skeletal muscle was not elucidated until the sophisticated mechanical experiments of the early s were performed Gordon et al. In its most basic form, the length-tension relationship states that isometric tension generation in skeletal muscle is a function of the magnitude of overlap between actin and myosin filaments.
Force-velocity Relationship The force generated by a muscle is a function of its velocity. Historically, the force-velocity relationship has been used to define the dynamic properties of the cross-bridges which cycle during muscle contraction.
The force-velocity relationship, like the length-tension relationship, is a curve that actually represents the results of many experiments plotted on the same graph.
Experimentally, a muscle is allowed to shorten against a constant load. The muscle velocity during shortening is measured and then plotted against the resistive force. The general form of this relationship is shown in the graph below. On the horizontal axis is plotted muscle velocity relative to maximum velocity Vmax while on the vertical axis is plotted muscle force relative to maximum isometric force Po.