1. The Organization of a Skeletal Muscle Figure 7-1

2. Organization of a Skeletal Muscle Fiber Figure 7-2a

3. Organization of a Skeletal Muscle Fiber Figure 7-2 b-c

4. Sarcomere Shortening Figure 7-3

5. Sarcomere Shortening Figure 7-3

6. Structure and Function of the Neuromuscular Junction Figure 7-4 a

7. Structure and Function of the Neuromuscular Junction Figure 7-4 b

8. Structure and Function of the Neuromuscular Junction Figure 7-4

9. Structure and Function of the Neuromuscular Junction Figure 7-4

10. Structure and Function of the Neuromuscular Junction Figure 7-4

11. Structure and Function of the Neuromuscular Junction Figure 7-4

12. Structure and Function of the Neuromuscular Junction

13. The Contraction Cycle Five Steps of the Contraction Cycle – Exposure of active sites – Formation of cross-bridges – Pivoting of myosin heads – Detachment of cross-bridges – Reactivation of myosin

14. Molecular Events of the Contraction Process Figure 7-5 The active site is exposed following the binding of calcium ions to troponin.

15. Molecular Events of the Contraction Process Figure 7-5 The myosin cross bridge forms and attaches to the exposed active site on the thin filaments.

16. Molecular Events of the Contraction Process Figure 7-5 The attached myosin head pivots toward the center of the sarcomere and ADP and a phosphate group are released.

17. Molecular Events of the Contraction Process Figure 7-5 The cross- bridges detach when the myosin head binds another ATP molecule

18. Molecular Events of the Contraction Process Figure 7-5 The detached myosin head is reactivated as it splits the ATP and captures the released energy.

20. Frequency of Muscle Fiber Stimulation Three Phases of Twitch – Latent period before contraction: The action potential moves through sarcolemma Causing Ca 2+ release – Contraction phase: Calcium ions bind Tension builds to peak – Relaxation phase: Ca 2+ levels fall Active sites are covered Tension falls to resting levels

21. Twitch and Development of Tension Figure 7-6

22. Effects of Repeated Stimulations Figure 7-7

23. Types of Skeletal Muscle Fibers Fast fibers (White) – Light in color, large diameter – Few capillaries, few mitochondria – Uses glycolysis (2 ATP) – Little myoglobin – Power/speed – Fatigue rapidly

24. Types of Skeletal Muscle Fibers Slow fibers (Red) Red in color, small diameter Many capillaries, numerous mitochondria Uses Krebs cycle/Oxidative phosphorylation (34 ATP) Much myoglobin High endurance

25. Muscle Metabolism Figure 7-9

26. Muscle Metabolism Figure 7-9

27. Muscle Metabolism Figure 7-9