9 TOB Muscle

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  1. Muscle Tissue consists of
    • muscle cells (myocytes, myofibers)
    • stem cells
    • neurons somatic + visceral motor, sensory (proprioception)
    • excitable plasma membranes
    • connective tissue
    • blood vessels
    • lymphatics
  2. What are the two types of non-muscle contractile tissue IN the muscle?
    • myoepithelial cells (glandular tissues)
    • myofibroblasts (fibroblasts that have developed contractile function, serve in wound healing)
  3. What are the there classifications of muscle?
    • 1. skeletal or visceral striated - voluntary
    • 2. cardiac striated - autonomic
    • 3. smooth NON-striated - autonomic
  4. voluntary muscle
    • skeletal striated - skeletal movement; cross and activate JOINTS (eg. bicep, tricep)
    • visceral striated - DON'T connect bone to bone; present in the upper esophagus, pahrynx, tongue, etc. can either be
    • indistinguishable from each other
    • striations run perpendicular to cell line
  5. cardiac striated
    • only found in the heart and is controlled autonomically
    • sympathetic speeds up heart beat, parasympathetic slows heart down
  6. smooth NON-striated
    • no striations; similar contractile elements as striated muscle, just organized differently
    • under autonomic control
    • found in the gut, bronchioles, blood vessels, ureter
  7. if a word has myo-, sarco-, or -mysium in it:
    • it's referreing to muscle
    • mysium means flesh
  8. sarcolemma
    muscle cell plasma membrane including the external lamina (similar to a basal lamina)
  9. sarcoplasm
    muscle cell cytoplasm
  10. sarcoplasmic reticulum
    muscle cell smooth ER; important for calcium storage
  11. names for muscle cells
    myofiber, myocyte
  12. skeletal muscle cells
    • run the full length of the muscle
    • are unbranched, striated & multinucleated (needed because of how long they are)
    • controlled voluntarily
    • continuous external lamina
    • NO gap junctions (UNLIKE cardiac/smooth muscle the whole muscle cell is insulated from it's surroundings)
  13. 3 levels of muscle connective tissue investments
    • 1. endomysium - surrounds each individual muscle cell
    • 2. perimysium - CT around each fascicle (group of cells)
    • 3. epimysium - outside the muscle itself
  14. What are two atypical striated muscles?
    • lower pharynx
    • diaphragm
  15. muscle cell cytoplasm (sarcoplasm) is filled with:
    CONTRACTILE elements, mainly actin and myosin; these are what push the nuclei off to the periphery of the cells
  16. Image Upload
    • skeletal muscle (whole mount)
    • can see STRIATIONS
    • can see muscle cells running from L to R diagonally
    • nuclei pushed to periphery
    • striations running 'horizontally' within cells
  17. myofibrils
    • the dark and light regions that identify striated muscle as 'striated'
    • each myofibril is made up of sarcomeres that are in sync with adjacent sarcomeres
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    • sarcomere exists from the Z (dark) line in one thin actin filament to the Z line in the next
    • I band: thin actin filament bisected by the Z line; light staining
    • Z line: serves as an anchoring point for thin actin filaments (Z disk)
    • A band: thick myosin filaments; dark staining
    • M line: line with proteins that reside in the middle of the A (thick myosin) band which hold the myosin together
    • H band: slightly lighter area surrounding M line in the A (myosin) band
    • the bubbly/dotty stuff between myofibril striation = cell organelles
  19. muscle contraction
    • occurs by filament sliding mechanism
    • the sarcomere overall shortens
    • the Z-lines MOVE closer together
    • neither the I nor A bands shorten (Z within the I just moves)
    • H band (surrounding M line) disappears - is filled in with thin filaments

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  20. tropomyosin
    • protein located on the surface of actin
    • in the absence of calcium, it BLOCKS the active sites of actin
    • when calcium is present, it changes tropomyosin's conformation --> actin and myosin can now interact (+ ATP) and provide muscle contraction
    • control of muscle contraction has a lot to do with Ca 2+
  21. How do motor neuron action potentials propagate through a bundle of muscle cells?
    • neuron meets muscle at motor endoplate, aka neuromuscular junction
    • action potential impulse can be transferred to surface of muscle cell membrane
    • How can this signal go deep into the muscle & interact with calcium stores?
    • *T tubule: indentation of plasma membrane that runs DEEP into the muscle (surrounds myofibrils)
    • cisterns of smooth ER also surround T tubules, and they're filled with CALCIUM (structure is overall called a triad)
    • action potential -> T tubule -> sarcoplasmic reticulum -> voltage gated Ca 2+ channels enter -> cell cytoplasm
  22. dystrophin complex
    • connects actin cytoskeleton (thin filaments) to cell's plasma membrane which is itself linked to the connective tissue by another dystrophin-associated complex
    • ~links cell contractile elements to the surrounding connective tissue to mobilize muscles connected to tendon

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    • located around cell periphery (brown staining)
  23. dystrophin complex deficiency
    • LOSE the ability to transfer mechanical force to move muscles (contractile elements NOT connected to CT)
    • hypercalcemia also results, leading to increased osmosis --> mitochondrial rupture
    • eg. muscular dystrophy - only some cells have dystrophin

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  24. Duchenne Muscular Dystrophy
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    • muscle fiber atrophy; varied muscle fiber size
  25. Becker's Muscular Dystrophy
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    • replacement of muscle tissue with fat (adipose tissue)
    • CALVES are especially susceptible (gastrocnemius & soleus muscle) experience pseudohypertrophy
  26. muscular control is dependent on:
    • motor & sensory components:
    • 1) muscle fiber types
    • 2) motor unit density
    • 3) sensory fibers - that give us sense of propioception
  27. What are two different muscle fiber types?
    • RED (slow twitch): many mitochondria & oxidative enzymes (AERobic); don't contract fast but CAN contract for long periods without fatiguing; eg. back muscles
    • WHITE (fast twitch): bigger muscle cells, contract quickly; fewer mitochondria & oxidative enzymes (ANaerobic); quicker to fatigue; eg. quadraceps

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  28. motor unit density
    • fine control: few muscle fibers per single neuron (splits maybe 3-4 times) --> MORE control
    • coarse control: lots of muscle fibers per single neuron (can split ~1,000 times) --> LESS control
  29. muscle fiber sensory perception
    • provide proprioceptive information because they're made up of muscle cells & nerves
    • 1. muscle spindle
    • 2. golgi tendon organs
  30. muscle spindle
    • combination of muscle fibers + afferent nerves that monitor the extent to which muscles are extended or relaxed
    • muscle spindle cross-section
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  31. golgi tendon organ
    • Image Uploadlocated in the tendon and provide sensory information about how much a muscle is being stretched
    • involved in both proprioception AND inhibition reflex
  32. inhibition reflex
    reflex activated by golgi tendon organ that causes a muscle being overstretched and about to tear from the tendon to relax (also causes a positive response for an opposite muscle to contract)
  33. Image Upload
    • cardiac muscle
    • also striated
    • only found in the heart
    • under autonomic control
    • relatively short cells connected by end-to-end junctions
    • DISCONTINUOUS external lamina - there are gap junctions between cells
    • binucleate cells
    • CT = endocardium & epicardium
  34. Image Upload
    • cardiac muscle
    • can see cell BRANCHING
    • can see centered nuclei (unlike skeletal, pushed to the periphery)
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    • A = fascia adherens, perpendicular to long line of cell
    • B = intercalated disc, parallel to the cell, is where most cell-cell communication (gap junctions) occur
    • desmosomes can exist in BOTH places
  36. Image Upload
    • shows two cells interaction and delineations between them
    • horizontal = fascia adherens (coincide where Z lines are located)
    • vertical = intercalated discs
    • desmosomes can be present at both sites
    • functions in linking and anchoring
  37. Image Upload
    • left: cardiac muscle (central nuclei)
    • right: skeletal muscle (periphery nuclei)
    • the white spots inside the cells = myofibrils for both tissue types
  38. cardiac muscle has less robust smooth ER for T tubule activation
    • called a diad (sarcoplasmic reticulum + T tubule because there's less smooth ER surrounding the plasma membrane (T tubule) invagination
    • LESS efficient than skeletal muscle but that's okay b/c cardiac muscle has GAP JUNCTIONS for communication
    • it can also spontaneously contract
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    • endocrine cells
    • specialized myocardial (muscle) cells that can contract & secrete ANF (Atrial Natriuretic Factor) to surrounding cardiac cells (small black dots = granules)
  40. ANF (Atrial Natriuretic Factor)
    hormone released by endocrine cells in cardiac muscle that acts as a vasodilator in response to high BP, high Na+, & angiotensin II (a vasoconstrictor)
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    • Purkinje fibers
    • specialized myocardial cells that can contract and conduct impulses/signals
    • exist just deep of the endocardial surface near lumen of ventricles where blood is
    • are rich in glycogen (cells look filled with space)

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  42. Smooth Muscle
    • non-striated
    • involuntary (under autonomic control)
    • discontinuous external lamina
    • fewer CT investments (CT = epimysium & endomysium only)
    • many gap junctions
    • found throughout hollow organs of body (eg. GI tract, blood vessels, bladder, & arrector pili in skin)
  43. Image Upload
    • smooth muscle
    • can often see both longitudinal and cross-sectional view in the same section
    • spindle like cells
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    • dense body
    • smooth muscle cells have similar contractile units as skeletal/cardiac striated
    • except instead of being anchored on a Z line, smooth muscle contractile elements are anchored on spots known as dense bodies
  45. The Different Ways Smooth Muscle can Contract
    • 1. electrically: via gated Ca2+ channels
    • used by single (common BVs, GI tract) & multiunit (restricted trachea, large elastic arteries, iris)
    • 2. mechanically: receptors in smooth muscle that facilitate stretching; stimulates mechano-sensitive ion channels ("myogenic" response) - NOT a nerve response
    • 3. hormonally: e.g. oxytocin stimulates uterine contractions
  46. caveolae
    • indentation in smooth muscle cells which allow propagation of nerve impulses and Ca 2+ activated channels throughout a smooth muscle
    • analogous to T tubules in striated muscle
  47. muscle repair
    satellite (stem) cells reside in external lamina; activated in damage or injury, proliferate, and replace damaged muscle cells
  48. skeletal muscle repair
    comes about as a result of disease (eg. muscular dystrophy) or damage (eg. small tears from excessive weight training)
  49. weight lifting causes ___________, not ________
    • weight lifting causes hypertrophy, not hyperplasia
    • you're increasing cells' SIZE, not their number
  50. cardiac muscle repair
    • satellite cell replacement as well as limited mitosis
    • most repair is fibrotic - fibrous scar that can hinder how the heart beats
    • limited though: most you start with is what you end with
  51. smooth muscle repair
    actively proliferates in throughout life in response to damage or physiological needs (e.g. uterine expansion during pregnancy)
  52. Image Upload
    • can see sarcomeres
    • the stuff innervating sarcomeres = CYTOPLASM, or sarcoplasm
    • sarcoplasm is mostly made up of smooth ER (sarcoplasmic reticulum), however there are other organelles as well
    • dark blobs = mitochondria
    • probably also some lysosomes/ribosomes
  53. Image Upload
    • dark horizontal lines (fascia adherens) & branching are clues that a slide = cardiac muscle
    • also centered nuclei/striations
    • in between spaces = endocardium
  54. Image Upload
    • arrow = gap junction
    • horizontal squiggles = fascia adherens
    • cardiac muscle
  55. Image Upload
    • cardiac muscle
    • can see purkinje fibers, usually seen in context of free surface cause they're close to heart's lumen, where blood pumps through
    • lots of clear spaces = glycogen

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  56. Image Upload
    • you know this is smooth muscle because you see cross-section and longitudinal muscle
    • this is what's need for peristalsis --> must be smooth muscle
Card Set:
9 TOB Muscle
2016-09-15 15:55:23
TOB Exam2
MBS TOB Exam 2
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