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MUSCLE PHYSIOLOGY

MUSCLE PHYSIOLOGY. CHAPTER 11. I. MUSCLES. 600+ 40-50% of body weight. 3 Types of muscle. 1. Skeletal 2. Cardiac 3. Smooth **majority of chapter will be focused on skeletal muscle. II. Functions of Skeletal Muscle. Movement Posture Support Guard entrances/exits

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MUSCLE PHYSIOLOGY

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  1. MUSCLE PHYSIOLOGY CHAPTER 11

  2. I. MUSCLES • 600+ • 40-50% of body weight

  3. 3 Types of muscle • 1. Skeletal • 2. Cardiac • 3. Smooth • **majority of chapter will be focused on skeletal muscle

  4. II. Functions of Skeletal Muscle • Movement • Posture • Support • Guard entrances/exits • Body Temperatures

  5. III. Anatomy of Skeletal Muscle a. Skeletal muscle contains bundles of skeletal muscle fibers. • The cells actually called fibers

  6. b. Components of skeletal muscle • Connective tissue • Blood vessels • nerves

  7. c. Connective Tissue A. Fascia - connective tissue found underskin and surrounding deeper organs B. Epimysium - covers entire muscle • Surounded by fascia C. Perimysium - covers fasicles or groups of skeletal muscle fibers • Within epimysium • Tough connective tissue D. Endomysium - covers skeletal muscle fiber Delicate connective tissue within perimysium

  8. MUSCLE

  9. IV. TENDON • Epimysium, perimysium, and endomysium continue beyond the muscle to form the tendon of a muscle • Connect muscle to bone • Tough connective tissue • Aponeuroses - merging of tendons to create a flat strong connective tissue

  10. TENDON

  11. d. Blood vessels • Innovate muscles to provide nourishment muscle needs to function and rid of wastes.

  12. e. Nerves • Innovate muscles to control movements

  13. IV. Overview of Skeletal Muscle/fiber • Composed of bundles of skeletal muscle fibers that run entire length • Have same structural parts as cells just different names

  14. a. Structures found in skeletal muscle • Multinucleated • Sacrolemma • Sarcoplasm • Sarcoplasmic reticulum • Mitochondria • Myofibrils • Sarcomere

  15. Skeletal Muscle Cell

  16. i. multinucleated • Muscle have many nuclei • Allows to make ribosomes which important for protein synthesis

  17. ii. Sarcolemma • Plasma membrane of muscle fiber

  18. iii. sarcoplasm • Cytoplasm of muscle cell

  19. iv. Sarcoplasmic reticulum • Network of tubules and sacs • Equates to ER • Contains Calcium ions • Plays a role in muscle contraction

  20. v. mitochondria • Many mitochondria • To produce ATP

  21. vi. myofibrils • Bundles of very fine fibers • Extend lengthwise along skeletal fibers • Made of thick and thin myofilaments

  22. vii. sarcomere • Basic unit of the muscle • Like an osteon is to bone

  23. V. Structure of Sarcomere

  24. Structure cont…. • A band • Entire length of THICK filaments • Within A band is • M line - line down the middle of thick filament • H zone - middle region of THICK filaments ONLY • Zone of overlap - where thick and thin fibers overlap

  25. Structure cont…. • I band • Segment that includes the Z line and ends of THIN filaments. • THIN filaments ONLY

  26. c. Z lines • Signif a sarcomere • Z line to Z line = 1 sarcomere • Many sarcomeres make up a myofibril

  27. d. Transverse Tubules • T-tubules • Run transversely across sarcoplasm and rt. angles to long axis of the cell • Formed by inward extensions of sarcolemma • Function - allows electrical impulses traveling along sarcolemma to move deeper into the cell

  28. e. Triad • T-tubules sandwiched between 2 sarcolemma reticulum • Important because impulse travels through t-tubules and stimulates release of Ca+ needed for contraction

  29. Sarcomere

  30. Sarcomere

  31. Triad

  32. f. Myofibrils • Each muscle fiber contains thousands of subunits called myofibrils • Within myofibril are thick and thin myofilaments

  33. i. Thin myofilament • Made from 3 proteins 1. Actin 2. Tropomyosin 3. troponin

  34. 1. Actin • Globular • Bead like strand of protein • Twists around each other to form bulk of thin filament • Chemically attracted to myosin

  35. 2. Tropomyosin • Strand of protein that twists around actin

  36. 3. Troponin • Spaced at intervals • Blocks active sites (on actin) needed for muscle contraction

  37. Actin, troponin, tropomyosinThin filament

  38. ii. Thick Filament 1. Myosin • Shaped like golf clubs 2. Long flat shafts bundled together to form their crossbridges (heads) • Heads stick out and are chemically attracted to actin active site of thin filament

  39. Myosin

  40. VI. Muscle Physiology • Sliding filament theory i. As a result of contraction H zone gets smaller I band smaller Zone overlap larger Z lines closer together A band - same Fibers shorten by 30% When I band completely gone, contraction ends. Thin filaments sliding toward center of sarcomere along side of the thick filaments

  41. b. Nervous Stimulation of contraction i. Motor neuron - nerve that sends signal • Action potential - the actual signal • Motor end plate-where motor neuron meets sarcolemma(forms neuromuscular junction) • Neuromuscular junction- contact point between nerve and muscle

  42. CONTRACTION • Muscle contraction has 3 phases • Latent • Contraction • relaxation

  43. i. Latent stage of contraction • Action potential (nerve impulse) of motor neuron reachs motor end plate, neurotransmitters (acetylcholine) released into synaptic cleft -goes across sarcolemma to excite cell • The Ach diffuses across synaptic cleft and binds to receptors which changes the sacrolemma

  44. i. Latent Stage cont…. • Impulse travels over sarcolemma inward along T-Tubules which release Ca+ from Sarcoplasmic Reticulum (adjacent to T-tubules)

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