Histology #5 MSK muscle

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Author:
ARM
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239444
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Histology #5 MSK muscle
Updated:
2013-10-09 00:36:00
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Histo
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Histology #5 MSK muscle
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  1. Describe the 3 histological types of muscle
    • Smooth
    • -fusiform cells without striations
    • -vessels, uterus, gut, iris, etc...
    • Striated (skeletal and cardiac)
    • -cylindrical cells with densely packed arrays of contractile proteins visibly striated
    •          -Actin and myosin; titin (a structural protein)
  2. Describe the major morphological and functional characteristics of SMOOTH muscle
    • small fusiform cells with CENTRAL nuclei
    • individual cells arranged in sheets and tubes
    • contractile proteins- only visible on TEM
    •        -Actin (smooth muscle actin)
    •        - TropoMyosin, Myosin II
    • Intermediate filaments: desmin, vimentin
    • Dense body (desmosome attachments)
    • Gap Junctions (connexions)
    • Autonomic Innervation (stretch)
  3. describe the major morphological and functional characteristics of striated Cardiac muscle
    • Central nuclei
    • branching myofibres
    • Intercalated discs between cells (= anchorage region of cytoskeleton and rich in gap junctions)
    • relatively short length (50-100 microns)
    • rich in mitochondria (aerobic metabolism)
    • extensive SER- sarcoplasmic reticulum
    • vagus and purkinje fibre system innervation
  4. Describe the major morphological and functional characteristics of striated skeletal muscle
    • eccentric nuclei, long (10-50cm)
    • syncytial cell -trains of cells
    • prominent arrays of cytoskeletal contractile proteins- banding (birefringent)
    • abundant mitochondira
    • Extensive SER (smooth endoplasmic reticulum) aka sarcoplasmic reticulum
    •         -contains many voltage gated Ca++ channels
    • Extensive invaginations of plasma membrane
    •   -t tubules
    •   -triads include plasma membrane (the sarcolemma) and sarcoplasmic reticulum
  5. What are all the parts of the banding pattern
    • I band (gap between a bands)
    • A band (end of overlap zone to next end of overlap zone)
    • H zone: no overlap
    • Z line: z line to z line = sarcomere
    • M line: middle of sarcomere
  6. When a muscle fiber is stretched what happends?
    • increased distance between z lines
    • decreased zone overlap
    • increased width of H zone
    • A band remains constant
  7. What forms a triad?
    • T- tubules (sarcolemma invaginations)
    • sarcoplasmic reticulum
  8. Describe the morphological and functional specializations of the neuromuscular junction
    • ***Found in striated skeletal muscle
    • motor endplate: alpha motor neuron, releases ACh, R activated Na+ channel
    • site of BOTOX action (chemical neurectomy)
  9. Describe the morphological and functional characteristics of intrafusal muscle fibres
    • Individual striated skeletal muscle can be modified intrafusal muscle fibers
    • Proprioception (where you sense your position in space): sense stretch, indicate length/position
    • Reflex arc: sensory TYPE1A, motor (gamma motor neurons)
  10. List the connective tissue envelopes of skeletal muscle
    • epipysium: satellite cells, vessels, nerves
    • perimysium
    • endomysium
  11. What is a collagenous fibre network?
    • End to end
    • fuses to make tendon (myotendinous junction)
    • Golgi tendon organ stretch R (at R jxn determines tension)
  12. What is dystrophin?
    • Cytoplasmic rod-like protein
    • part of a protein complex that connects the myofibrils to the extracellular connective tissue components
    • important in transmitting loads from cells to tendon

    Absence/insufficiency = muscular dystrophy
  13. What is Myostatin
    • growth factor important in limiting muscle mass during development
    • mutations that make this protein non-functional are found in animals with exceptionally large muscles (double muscling eg Belgian blue cattle)
  14. What type of meat is fast twitch and which is slow twitch?
    • Light meat = fast twitch muscle (low myoglobin)
    • dark meat = slow twitch (endurance muscle, lots of myoglobin)

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