Skeletal muscle contraction

Skeletal muscle contraction

1. Skeletal Muscle Contraction

2. Structure of each muscle fibre and organisation

3. SARCOTUBULAR SYSTEM

4. Structure and Arrangement of Myosin Molecules Within Thick Filament

5. STRUCTURE OF SARCOMERE

6. STRUCTURE OF THICK AND THIN FILAMENTS

7. Banding pattern of skeletal muscle under microscope

8. Changes in Banding Pattern During Shortening

9. Excitation contraction coupling T Tubules and Sarcoplasmic Reticulum

10. DYSTROPHIN - GLYCOPROTEIN COMPLEX

11. MOLECULAR BASIS OF SKELETAL MUSCLE CONTRACTION Excitation – Contraction Coupling Actin – Myosin Interaction-Cross Bridge Formation & Cross – Bridge Cycling – Sarcomere Shortening Relaxation

12. Excitation Contraction Coupling The process by which depolarization of a muscle fibre initiates contraction is called excitation-contraction coupling . There has to be cross bridge activity in the muscle fibre following AP in the plasma membrane of muscle fibre .

13. Skeletal Muscle Contraction: EXCITATION CONTRACTION COUPLING Figure 12-11a: Excitation-contraction coupling

14. Figure 12-11b: Excitation-contraction coupling

15. Excitation contraction coupling

16. Role of Calcium in Cross-Bridge Formation During relaxed state

17. Role of Calcium in Cross-Bridge Formation Excited

18. Sliding Filament Mechanism Cross-bridge interaction between actin and myosin brings about muscle contraction by means of the sliding filament mechanism . Increase in Ca 2+ starts filament sliding Decrease in Ca 2+ turns off sliding process Thin filaments on each side of sarcomere slide inward over stationary thick filaments toward center of A band during contraction As thin filaments slide inward, they pull Z lines closer together Sarcomere shortens All sarcomeres throughout muscle fiber’s length shorten simultaneously Contraction is accomplished by thin filaments from opposite sides of each sarcomere sliding closer together between thick filaments.

19. Changes in Banding Pattern During Shortening

20. Power Stroke Activated cross bridge bends toward center of thick filament, “rowing” in thin filament to which it is attached Sarcoplasmic reticulum releases Ca 2+ Myosin heads bind to actin Hydrolysis of ATP transfers energy to myosin head and reorients it Myosin heads swivel toward center of sarcomere ( power stroke ) ATP binds to myosin head and detaches it from actin

21. Relaxation Depends on reuptake of Ca 2+ into sarcoplasmic reticulum (SR) Acetylcholinesterase breaks down ACh at neuromuscular junction Muscle fiber action potential stops When local action potential is no longer present, Ca 2+ moves back into sarcoplasmic reticulum

22. CROSS-BRIDGE CYCLE

23. &2 SKELETAL MUSCLE CONTRACTION

24. SKELETAL MUSCLE CONTRACTION

25. SKELETAL MUSCLE CONTRACTION

26. Cross Bridge Formation

27. RELAXATION OF SKELETAL MUSCLES

28. ROLE OF ATP 3 ROLES Provides the energy of the power stroke Causes detachment of myosin head from actin . Causes relaxation of muscle by supplying the energy for pumping back calcium into the terminal cistern

29. Difference between cardiac muscle and skeletal muscle contraction Cardiac muscle Single nucleus Gap junction- syncitium Diameter of cell-greater T tubules-large and lie at the level of Z line Release of Ca - Ca dependent Ca release Skeletal muscle Multinucleated No such Lesser T-tubule s lie at the junction of A-I Release of Ca -mechanical interaction between DHPR & RYR