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 actin filaments. You see, these actin filaments are actually going to have binding sites for myosin along their length. But, normally, these myosin binding sites are going to be covered by this protein called tropomyosin, which is basically wrapped around actin to block these myosin binding sites. And it's also going to have this attached protein called troponin. And this is going to be a calcium sensitive protein that when it binds calcium, it causes the tropomyosin to actually move and expose the myosin binding site on the actin 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 an action potential hitting the neuromuscular junction, and that that's 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 myosin filaments have what are called myosin heads. They're I like to think of them more as like grabby arms or something, and these are what are going to be used to sort of pull the myosin along the actin filament. Now, when the troponin binds calcium, causes the tropomyosin to expose those binding sites on actin, the myosin is going to attach to the actin filament. Now it's actually only going to attach if it has ATP bound. And, if it has ATP bound, it will go ahead and attach to the actin filament, like you see happening here. Let me actually go ahead and number these for us. So, that's going to be the first step, second step, and then right behind me, jump out of the way, you'll see step 3. This is where that ATP is going to be hydrolyzed and trigger what's known as the power stroke. Now that's basically going to be this sort of shape change in the myosin protein that you see here, where it hydrolyzes the ATP and releases the phosphate and the ADP, and it causes the head to essentially move in such a way that it pulls itself along the actin filament. 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 to this position, so it'll move, you know, this distance more or less. And once that ADP gets released, like we see happening right here in panel 5, the myosin is actually going to, bind another ATP and release from that actin filament, like we see happening here in panel 6. Now, this is, you know, 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, needs, you know, a bunch of those power strokes to, you know, get my muscles to 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 sarcomeres and then you actually see a big movement. So with that, let's go ahead and flip the page.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
47. Muscle Systems
Musculoskeletal System
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