3. بسم الله الرّحمن الرّحيم

4. Skeletal Muscle Mechanics By: Dr. Khurram Irshad

5. OBJECTIVES To Learn Structure of Skeletal Muscle Structure of Skeletal Muscle How muscle length shortens during the process of contraction How muscle length shortens during the process of contraction

6. Muscle Physiology Contraction Specialists Helps to maintain Homeostasis

7. Classification - Types i. Skeletal Muscles 40% of body weight i. Smooth Muscle 10% of body weight i. Cardiac Muscles

8. Classification of Muscles i. Striated - Skeletal muscles - Cardiac Muscle ii. Unstraited - Smooth muscles

9. i. Voluntary muscles - Skeletal muscles (Innervated by somatic nerves) nerves) ii. Involuntary muscles - Smooth muscles - Cardiac muscles (Innervated by autonomic nerves)

10. Structure of Skeletal Muscle

15. Molecular Basis of Skeletal Muscle Contraction Sliding Filament Theory

16. Cross Bridge Activity Rise in intracellular calcium ion Concentration Triggers cross bridge activity

18. Cross Bridge Cycle

19. The Tubules and Sarcoplasmic Reticulum

20. Simple (Single) Muscle Twitch

21. Excitation-Contraction Coupling

22. Skeletal Muscle Mechanics Muscles can produce contraction/power of different grades by 1. The number of muscle fibers contracting within a muscle. 2. Tension developed by each contracting fiber.

23. The number of muscle fibers contracting within a muscle

24. Tension develop by each contracting fiber  Frequency of stimulation.  The length of fiber at the onset of contraction.  The extent of fatigue.  The thickness of fiber.

25. Frequency of stimulation

26. The length of fiber at the onset of contraction

27. Source of energy required for skeletal muscle contraction and relaxation ATP Sources : 1. Stored ATP (only limited stores are available) 2. Creatine Phosphate (CP) 3. Oxidative Phosphorylation 4. Glycolysis.

28. Fatigue “Inability of a muscle to maintain a continuous tension for a prolonged period of time” Causes: i. Muscle Fatigue: - Accumulation of lactic acid - Depletion of energy stores

29. ii.Central Fatigue: iii.Neuro Muscular Fatigue:

30. Types of Muscle Contraction There are two types of muscle contraction. 1. Isotonic

31. ii. Isometric

32. Types of Muscle Fibers - Slow-oxidative (type I) fibers - Fast-oxidative (type IIa) fibers - Fast-glycolytic (type IIb) fibers

35. Thank you