1. How does muscle contract? N-

3. 1. Each skeletal muscle is composed of numerous fascicles…

4. 2. Each fascicle is composed of many muscle fibers/cells…

5. 3. The muscle fibers have color bands called striations.

7. 4. Each muscle fiber is composed of tiny myofibrils…

8. 5. The myofibril has a distinctive banding pattern (which is why the muscle fibers do.)

9. 6. Each myofibril is subdivided into units of contraction called sarcomeres.

10. 7. Each sarcomere has two types of filaments, the thick and thin
7. Each sarcomere has two types of filaments, the thick and thin. The thin filaments are made of the protein actin The thick filaments are made of the protein myosin
p.s. what’s wrong with this diagram?

11. (my apologies, but now you have to do a color drawing in your journal…)

12. 8. When these two types of filaments slide along each other, the sarcomeres shorten, even though the lengths of the actual filaments stay the same. This is the sliding-filament mechanism.

13. 9. And this causes muscles to contract
9. And this causes muscles to contract. Now let’s watch a little animation to explain a little more…