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Muscle Tissue

Muscle Tissue. Al M aarefa College. Objectives. Identify basic structure of Muscles Recognize types of muscular tissues and the difference between them Recognize the relation between structure and function of various muscular tissues . Tissues . Four fundamental tissues are recognized:

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Muscle Tissue

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  1. Muscle Tissue Al Maarefa College

  2. Objectives • Identify basic structure of Muscles • Recognize types of muscular tissues and the difference between them • Recognize the relation between structure and function of various muscular tissues

  3. Tissues • Four fundamental tissues are recognized: • Epithelial tissue • Connective tissue • Muscular tissue • Nervous tissue

  4. Muscle Tissue • Characteristics • Cells are referred to as fibers • Contracts or shortens with force when stimulated

  5. Special functional characteristics • Contractility • Only one action: to shorten • Shortening generates pulling force • Excitability • Nerve fibers cause electrical impulse to travel • Extensibility • Stretch with contraction of an opposing muscle • Elasticity • Recoils passively after being stretched

  6. Muscle function • Providing movement • Maintaining posture • Stabilizing joint • Generating heat

  7. Muscle Tissue Types • Skeletal: • attached to bones • Cardiac: • muscle of the heart • Smooth: • muscle associated with tubular structures and with the skin

  8. Skeletal muscle – Blood supply

  9. Skeletal Muscle • Nucleii are in periphery of cells, just under cell membrane

  10. Skeletal Muscle • A bands (dark-stained) • I bands (light-stained) • Z lines A bands I bands

  11. Skeletal Muscle

  12. Skeletal Muscle

  13. Skeletal Muscle Tissue Figure 4.14a

  14. Cardiac Muscle Tissue Figure 4.14b

  15. Cardiac Muscle Tissue

  16. Cardiac Muscle Tissue

  17. Cardiac Muscle Tissue

  18. Smooth Muscle Tissue

  19. Smooth Muscle Tissue

  20. Smooth Muscle Tissue

  21. Smooth Muscle Tissue

  22. Smooth Muscle Tissue

  23. Skeletal Muscle • Voluntary movement • Long and cylindrical • Transverse striation • Each fiber is multi-nuclear (multinucleated cells – embryonic cells fuse) • 40% of body weight

  24. Skeletal Muscle

  25. Smooth Muscle • Long, spindle shape • Not striated • Single nucleus • Involuntary movement • Internal organs

  26. Smooth Muscle

  27. Cardiac Muscle • Striations • Involuntary • One nucleus • Deep center • Heart muscle

  28. Cardiac Muscle

  29. Similarities… • Their cells are called fibers because they are elongated • Contraction depends on myofilaments • Actin • Myosin • Plasma membrane is called sarcolemma • Sarcos = flesh • Lemma = sheath

  30. Skeletal Muscle • Covering layers • Epimisium: surrounds the whole muscle • Perimesium: surrounds a muscle fascicle • Endomesium: surrounds each muscle fiber

  31. Skeletal Muscle Epimysiumsurrounds whole muscle Epimysiumsurrounds whole muscle

  32. Skeletal Muscle Perimysium Perimysium is around fascicle

  33. Skeletal Muscle Endomysium Endomysium is around each muscle fiber

  34. Some sites showing animations of muscle contraction • http://entochem.tamu.edu/MuscleStrucContractswf/index.html • http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/muscles/muscles.html

  35. Skeletal muscle • Fibers (each is one cell) have striations • Myofibrils are organelles of the cell: these are made up of filaments • Sarcomere • Basic unit of contraction • Myofibrils are long rows of repeating sarcomeres • Boundaries: Z discs (or lines) This big cylinder is a fiber: 1 cell -an organelle

  36. Myofibrils • Made of three types of filaments (or myofilaments): • Thick (myosin) • Thin (actin) • Elastic (titin) ______actin _____________myosin titin_____

  37. Depending on the distribution and interconnection of myofilaments a number of "bands" and "lines" can be distinguished in the sarcomeres : • I-band - actin filaments, • A-band - myosin filaments which may overlap with actin filaments, • H-band - zone of myosin filaments only (no overlap with actin filaments) within the A-band, • Z-line - zone of apposition of actin filaments belonging to two neighbouring sarcomeres • M-line - band of connections between myosin filaments.

  38. Sliding Filament Model __relaxed sarcomere__ _partly contracted_ fully contracted Sarcomere shortens because actin pulled towards its middle by myosin cross bridges “A” band constant because it is caused by myosin, which doesn’t change length Titin resists overstretching

  39. Another pic

  40. EM (electron microscope): parts of 2 myofibrils Labeled and unlabeled

  41. Sarcoplasmic reticulum is smooth ER • Tubules surround myofibrils • Cross-channels called “terminal cisternae” • Store Ca++ and release when muscle stimulated to contract • To thin filaments triggering sliding filament mechanism of contraction • T tubules are continuous with sarcolemma, therefore whole muscle (deep parts as well) contracts simultaneously

  42. Neuromuscular Junction Motor neurons innervate muscle fibers Motor end plate is where they meet Neurotransmitters are released by nerve signal: this initiates calcium ion release and muscle contraction • Motor Unit: a motor neuron and all the muscle fibers it innervates (these all contract together) • Average is 150, but range is four to several hundred muscle fibers in a motor unit • The finer the movement, the fewer muscle fibers /motor unit • The fibers are spread throughout the muscle, so stimulation of a single motor unit causes a weak contraction of the entire muscle

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