Muscle Physiology_Week 1_English (1).pptx

Muscle Physiology

1. Muscle Physiology Systems in Physiology 244 Dr Sanjeev Rambharose

2. COURSE CONTENT Chapter 8 – Muscle Physiology 1. Structure of Skeletal Muscle (Micro anatomy) Sarcomere Actin Myosin Troponin Tropomyosin Titin

3. COURSE CONTENT Chapter 8 – Muscle Physiology 2. Molecular basis of contraction (Sliding Filament Theory) Excitation Contraction Coupling 3. The Neuro-muscular Junction (Chapter 7)

4. COURSE CONTENT Chapter 8 – Muscle Physiology 4. Skeletal Muscle Mechanics (The Muscle Twitch and Factors that may influence it) Frequency of impulses (tetanus) Number of motor units Exhaustion Temperature Length of muscle fibers before contraction Load Types of contraction

5. COURSE CONTENT Chapter 8 – Muscle Physiology 5. Muscle Metabolism 6. Types of Muscle Fibres 7. Adaptations of Muscle Fibres with Exercise

6. Muscle Tissue Types Smooth Muscle Cardiac Muscle Skeletal muscle, also known as striated muscle or voluntary muscle. 30 – 40 % body weight

7. Muscle Tissue Types Short video that explains muscle tissue types. https://www.youtube.com/watch?v=eShBZ3-RxHA

8. Skeletal Muscle Cells known as muscle fibres Multiple nuclei per cell ( fiber ) Attached to bones – Facilitates movement

9. Skeletal Muscle Fiber Myofibril Myofibrils are specialized contractile elements Contain highly organized microfilaments Thick and thin filaments

10. Skeletal Muscle Structure

11. The functional unit or sarcomere A myofibril displays alternating dark bands (the A bands) and light bands (the I bands) A band – stacked set of thick filaments along with the portions of the thin filaments Middle of A band – H zone M line – supporting proteins I band – Thin filaments that don’t project into the A band Z line Sarcomere

12. The functional unit or sarcomere Growth – increase in length by adding new sarcomeres Titin Scaffolding Elastic spring Signal transduction

13. Myosin A myosin molecule is a protein shaped somewhat like a golf club Myosin can bend at hinge points in two locations Heads form the cross bridges Actin binding site Myosin ATPase site

14. Actin Thin filaments contain 3 proteins: Actin Tropomyosin Troponin Tropomyosin – covers the actin sites that bind with the cross bridges. Troponin - stabilizes tropomyosin in its blocking position over actin’s cross-bridge binding sites The thin or actin filaments The regulatory prot.troponin & tropomyosin

15. Role of Calcium in turning on cross bridges

16. Check Your Understanding 1. Compare the relationship among myofibrils, muscle fibers , and a whole muscle. 2. Illustrate the relative positions of the cytoskeletal structures that make up a sarcomere. 3. Describe how actin, tropomyosin, and troponin are organized in a relaxed muscle fiber .

17. Molecular Basis of Skeletal Muscle Contraction How does cross-bridge interaction between actin and myosin bring about muscle contraction? How does a muscle action potential trigger this contractile process? What is the source of the Calcium that permit crossbridge binding?

18. Sliding Filament Theory Thin filaments on each side of a sarcomere slide inward over the stationary thick filaments toward the A band’s center during contraction. Thin filaments pull the Z lines closer together, so in effect the sarcomere shortens. All sarcomeres throughout the length of the Muscle fiber shorten simultaneously – entire muscle fiber shortens

19. Power Stroke Myosin cross bridges “walk” along an actin filament to pull it inward relative to the stationary thick filament. When actin and myosin bind, myosin’s head tilts inward Bending at this neck hinge point creates a “stroking” motion Thin filament is pulled toward the center of the sarcomere Power stroke of a cross bridge

20. Contracting Muscle

21. Contracting Muscle

22. Contracting Muscle

23. Skeletal Muscle Contraction Please refer to Memo1 - Skeletal Muscle Contraction for more details in English and Afrikaans.