1. Fig. 10-3. Myofibrils are surrounded by calcium- containing sarcoplasmic reticulum.

2. Fig. 10-7. Review of thin and thick filament structure

3. Fig. 10-9. Overview of the process

4. The muscle fiber is stimulated.

5. Fig. 10-9. Overview of the process The muscle fiber is stimulated. Ca 2+ ions are released.

6. Fig. 10-11. “End- on” view of thick & thin filaments, showing the effect of calcium ions after release from the S.R.

7. Fig. 10-9. Overview of the process The muscle fiber is stimulated. Ca 2+ ions are released.

8. Fig. 10-9. Overview of the process The muscle fiber is stimulated. Ca 2+ ions are released. Thin filaments move to middle of sarcomere.

9. Fig. 10-12 Calcium attaches to troponin/ tropomyosin; they roll away, exposing the active site on actin.

10. Fig. 10-12 Myosin cross-bridges attach to active site on actin. After attachment, the cross-bridges pivot, pulling the thin filaments.

11. Fig. 10-12 A fresh ATP replaces the ADP+P i, allowing myosin and actin to detach. Energy from the splitting of the fresh ATP allows repositioning of the myosin head.

12. Fig. 10-12 This leads back to Step 1, which continues the cycle as long as calcium ions are attached to troponin/tropomyosin.

13. Fig. 10-9. Overview of the process The muscle fiber is stimulated. Ca 2+ ions are released. Thin filaments move to middle of sarcomere.

14. Fig. 10-9. Overview of the process The muscle fiber is stimulated. Ca 2+ ions are released. Thin filaments move to middle of sarcomere. Muscle fiber contracts.

15. Fig. 10-9. Overview of the process The muscle fiber is stimulated. Ca 2+ ions are released. Thin filaments move to middle of sarcomere. Muscle fiber contracts. Muscle tension increases.