We're kicking off our exploration of muscles with a look at the complex and important relationship between actin and myosin. Your smooth, cardiac, and skeletal muscles create movement by contracting and releasing in a process called the sliding filament model. Your skeletal muscles are constructed like a rope made of bundles of protein fibers, and that the smallest strands are your actin and myosin myofilaments. Its their use of calcium and ATP that causes the binding and unbinding that makes sarcomeres contract and relax.

Table of Contents
Smooth, Cardiac, and Skeletal Muscles Create Movement 1:18
Sliding Filament Model 4:52
Skeletal Muscles Are Made of Bundles of Protein Fibers 2:40
Actin and Myosin Myofilaments 3:54
Calcium and ATP Cause the Binding and Unbinding 5:05

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1. Introduction to Anatomy & Physiology
2. Tissues, Part 1
3. Tissues, Part 2 - Epithelial Tissue
4. Tissues, Part 3 - Connective Tissues
5. Tissues, Part 4 - Types of Connective Tissues
6. The Integumentary System, Part 1: Skin Deep
7. The Integumentary System, Part 2: Skin Deeper
8. The Nervous System, Part 1
9. The Nervous System, Part 2: Action! Potential!
10. The Nervous System, Part 3: Synapses!
11. Central Nervous System
12. Peripheral Nervous System
13. Autonomic Nervous System
14. Sympathetic Nervous System
15. Parasympathetic Nervous System
16. Taste & Smell
17. Hearing & Balance
18. Vision
19. The Skeletal System
20. Joints
21. Muscles, Part 1 - Muscle Cells
22. Muscles, Part 2 - Organismal Level
23. Endocrine System, Part 1 - Glands & Hormones
24. Endocrine System, Part 2 - Hormone Cascades
25. The Heart, Part 1 - Under Pressure
26. The Heart, Part 2 - Heart Throbs
27. Blood Vessels, Part 1 - Form and Function
28. Blood Vessels, Part 2
29. Blood, Part 1 - True Blood
30. Blood, Part 2 - There Will Be Blood
31. Respiratory System, Part 1
32. Respiratory System, Part 2
33. Digestive System, Part 1
34. Digestive System, Part 2
35. Digestive System, Part 3
36. Metabolism & Nutrition, Part 1
37. Metabolism & Nutrition, Part 2
38. Urinary System, Part 1
39. Urinary System, Part 2
40. Reproductive System, Part 1: Female Reproductive System
41. Reproductive System, Part 2: Male Reproductive System
42. Reproductive System, Part 3: Sex & Fertilization
43. Reproductive System, Part 4: Pregnancy & Development
44. Lymphatic System
45. Immune System, Part 1
46. Immune System, Part 2
47. Immune System, Part 3

In this Crash Course series, Hank Green teaches most of what you should know about anatomy and physiology, perfect for a freshman-level biology course, or just your own curiosity about the human body.