Sliding Filament Model

by Jason Amores Sumpter
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the mechanism that explains how the thin and thick filaments slide past each other to cause contraction is known as the sliding filament model. Now it's going to involve some proteins that interact with acting filaments. You see, these acting filaments are actually going to have binding sites for my assassin along their length. But normally these Mayas and binding sites are going to be covered by this protein called trope um, IAS in, which is basically wrapped around acting to block these Mayas and binding sites. And it's also gonna have this attached protein called troponin and this is it going to be a calcium sensitive protein that when it binds calcium, it causes the trope, um, Eliasson toe actually move and exposed the my it's, um, binding site on the acting filament. Now we'll talk in a little bit about where this calcium comes from, so for now, I don't want you to worry too much about it. Just know that it's going to be due to, uh, an action potential hitting the neuromuscular junction and that that's, you know, essentially, just think of it as a synaptic signal that's going to trigger this calcium release, and we'll go into the details in just a little bit. Now the Maya Seuin filaments have what are called Miocene heads there. I like to think of the Maura's like grab the arms or something and these air what air going to be used to sort of pull the myson along the act in filament. Now, when the troponin binds, calcium causes the trophy Maya's into expose those binding sites on acting, the myson is going to attach to the acting filament. Now it's It's actually only gonna attach if it has a teepee bound and if it has eight p bound, it will go ahead and attach to the acting filament like you see happening here. Let me actually go ahead and number of these for us. So that's gonna be a first step. Second step, and then right behind me, jumping out of the way. You'll see Step three. This is where that 80 p is going to be hydrolyzed and trigger what's known as the power stroke. Now, that's basically gonna be this uhh sort of shape change in the Miocene protein that you see here where it hide. Relies is the 80 p and releases the phosphate and the ADP, and it causes the head. Thio essentially move in such a way that it it pulls itself along the acting filaments. So here you can see they're trying to show the difference in the angle that it takes. Same with what's going on here. So essentially, that head is going, you know, from this position, thio this position so it'll move. You know, this distance more or less. And once that a deep gets released like we see happening right here in panel five, Uh, the myson is actually going to bind another 80 p and release from that acting filament like we see happening here in panel six. Now, this is essentially one little step that will have to be repeated many, many, many times to cause, you know, the big muscle contractions like, you know, I mean, even just this is, uh, needs, you know, a bunch of those power strokes toe get my get my muscles toe crank like that, you know? So the point is, this is going to be repeated many, many times. This just causes, like, one little movement. But you add a ton of these together, you know, in all those Arkham ears, and then you actually see a big movement as a result. So with that, let's go ahead and flip the page.