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Understanding Muscle Properties: Contractibility, Excitability, Extensibility, and Elasticity

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jemima-young
66 diapositives · 832 Views · Nov 13, 2014

Muscle tissue exhibits four fundamental properties: contractibility, excitability, extensibility, and elasticity. Contractibility allows muscle cells to shorten and generate force, while excitability enables them to respond to stimuli, such as nerve impulses and hormones. Extensibility refers to the ability to stretch without losing function, and elasticity allows muscles to return to their original shape after contraction. There are three main types of muscles: skeletal, cardiac, and smooth, each with distinct structures and functions essential for body movement and organ function.

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  1. Muscle System Ch 9

  2. Muscle Properties • 4 basic properties • Contractability • Excitability • Extensibility • Elasticity

  3. Contractability • Cells capable of decreasing along a longitudinal axis • Shorten & thicken • Produce force • Pull or create tension

  4. Contractability

  5. Excitability • Ability to respond to external stimulation • Stimulation initiated by • Hormonal cues • nerves • Motor nerves

  6. Extensibility • Ability to “stretch” without loss of function

  7. Elasticity • Ability to regain original shape following contraction

  8. Muscle Types • Skeletal • Cardiac • Smooth

  9. Skeletal • Aka muscle fiber • Primary muscle type • 700+ • Voluntary • Only consciously controlled tissue • Move & stabilize the skeleton • Striated • Contractile proteins produce movement (contraction), striated in appearance • Large, multinucleate cells • Long thin cells= myofibers • Some regeneration

  10. Skeletal Muscle

  11. Striation

  12. Skeletal

  13. Skeletal Muscle Function • By mean of contractions..

  14. Skeletal Muscle Functions • Produce skeletal movement • Maintain posture & position • Support soft tissue (pelvic floor & abdominal wall) • Regulate entering & exiting of material • Digestive & urinary tract • Thermogenic • Produce body heat

  15. Motor Control • Controlled by higher brain regions (Cerebrum) • Allow for conscious control of muscles

  16. Smooth • Aka visceral • Non-striated aka smooth • Involuntary • Not consciously controlled • Small spindle shaped cells • Microfibers with random arrangement • Uninucleate • Regenerative • Functions in transporting fluids & solids through the body • Ex digestive system, urinary structures, blood vessels, glands, reproductive tract

  17. Smooth Muscle

  18. Cardiac • Involuntary striated • Self stimulating • Only in heart • Small, uninucleate, interconnected, branched cells • Intercalated discs • Visible cellular connections • Gap junctions • Desmosomes • Functions to push blood through blood vessels • No regeneration

  19. Cardiac

  20. Cardiac

  21. Skeletal Muscle Anatomy • Specialized cells- Myofibers • Long slender fiber like cells • Mature cells multinucleate • NOT capable of mitotic division • Cellular development • Fusion of many embryonic stem cells form long multinucleate cells • myoblasts

  22. Myofiber

  23. Myofibers

  24. Skeletal Muscle Cellular Development

  25. Myofibers

  26. Myofiber Structure • Sarcolemma • Myofiber cell membrane • Sarcoplasm • Myofiber cytoplasm • Made up of bundles of myofibrils • Made up of micrfilaments aka myofilaments • Satallite cells • Muscle stem cells • Resident myoblasts in adult tissue • Tissue repair • Fascicle • Connective tissue holds together for organization • Contains bundles of myofibers

  27. Myofiber

  28. Sarcolemma

  29. Sarcoplasm

  30. Satellite Cells

  31. Myofibers are made of bundles of Myofibrils Aka Fascicle

  32. Myofibrils are bundles of Myofilaments

  33. Muscle Connective Tissue • Connective tissue surrounds, supports, & attaches muscle • 3 layers of connective tissue • Endomysium • Perimysium • Epimysium

  34. Endomysium • “Within” • CT surrounding & binding together individual myofibers • Delicate network of reticular fibers • Holds myofibers together • Supports blood vessels • House satellite cells

  35. Endomysium surrounds & binds together individual myofibers

  36. Endomysium

  37. Endomysium- Normal Cells

  38. Perimysium • “around” • CT surrounding & binding groups of myofibers • Fascicles • Stringiness of meat • Collagen & elastic fibers • Houses blood vessels & nerves

  39. Perimysium surrounds & binds groups of myofibers

  40. Perimysium- Cross Section

  41. Perimysium- Longitudinal Section

  42. Perimysium anchors blood vessels & nerves

  43. Perimysium bundles a fascicle

  44. Epimysium • “above” • Dense irregular CT • Surrounds & binds fascicles together • Holds together Individual muscles into discrete units • Ex biceps, triceps, deltoid

  45. Epimysium holds together Individual muscles into discrete units

  46. Epimysium

  47. Tendons & Aponeurosis • CT attaching • Muscle to bone • Muscle into CT of another muscle • Combination of CT fibers from all levels of muscle organization • Endomysium • Perimysium • Epimysium • CT fibers are continuous w/ periosteum & osseous matrix= strong muscle attachments • Bones more likely to break before tendon tears away from bone • All CTs merge to form attachments • Tendon- strong cord or rope • Aponeurosis- flattened sheet