1. MUSCLES LECTURE 14 CHAPTER 12 MECHANISMS OF CONTRACTION

2. MUSCLE STRUCTURE

3. Skeletal muscle cells (fibers) are multinuclear and have striations - under voluntary control; but also responds to reflexes.

4. STRUCTURE OF SKELETAL MUSCLE Figure 12.1

5. You should know everything on this slide from anatomy: --- Origin/Insertion --- flexor muscles/extensor muscles --- prime mover = agonist; in a flexion, the flexor is the agonist, and the extensor is the antagonist.

6. What’s Inside A Muscle Fiber (cell)?

7. Myofibrils contain myofilaments arranged into sarcomeres

8. Titin Filaments and M Lines M = Midline

9. Arrangement of Thick and Thin Filaments

10. HOW DOES A MUSCLE WORK?

12. Fig. 7.23

13. Fig. 7.26

14. Fig. 7.28

16. Review: Stimulating a Muscle Fiber

17. Stimulating a Muscle Fiber

19. ROLE OF CALCIUM

20. CLOSE UP OF POWER STROKE

21. REVIEW OF INTERACTION OF MYOSIN WITH ACTIN Click here to watch

22. Sliding Filament Theory of Muscle Contraction When a muscle contracts, sarcomeres (distance between the Z-lines shortens).

23. Muscle Relaxation a. Action potentials cease. b. Calcium release channels close c. Ca 2+ -ATPase pumps move Ca 2+ back into SR (active transport). d. No more Ca 2+ is available to bind to troponin e. Tropomyosin moves to block the myosin heads from binding to actin

24. Motor Units