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
    • 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
  16. 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
    • 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
  17. 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

  18. 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+
  19. 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
  20. 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

    • located around cell periphery (brown staining)
  21. 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

  22. Duchenne Muscular Dystrophy
    • muscle fiber atrophy; varied muscle fiber size
  23. Becker's Muscular Dystrophy
    • replacement of muscle tissue with fat (adipose tissue)
    • CALVES are especially susceptible (gastrocnemius & soleus muscle) experience pseudohypertrophy
  24. 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
  25. 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

  26. 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
  27. muscle fiber sensory perception
    • provide proprioceptive information because they're made up of muscle cells & nerves
    • 1. muscle spindle
    • 2. golgi tendon organs
  28. muscle spindle
    • combination of muscle fibers + afferent nerves that monitor the extent to which muscles are extended or relaxed
    • muscle spindle cross-section
  29. golgi tendon organ
    • located in the tendon and provide sensory information about how much a muscle is being stretched
    • involved in both proprioception AND inhibition reflex
  30. 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)
    • 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
    • cardiac muscle
    • can see cell BRANCHING
    • can see centered nuclei (unlike skeletal, pushed to the periphery)
    • 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
    • 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
    • left: cardiac muscle (central nuclei)
    • right: skeletal muscle (periphery nuclei)
    • the white spots inside the cells = myofibrils for both tissue types
  31. 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
    • endocrine cells
    • specialized myocardial (muscle) cells that can contract & secrete ANF (Atrial Natriuretic Factor) to surrounding cardiac cells (small black dots = granules)
  32. 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)
    • 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)

  33. 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)
    • smooth muscle
    • can often see both longitudinal and cross-sectional view in the same section
    • spindle like cells
    • 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
  34. 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
  35. 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
  36. muscle repair
    satellite (stem) cells reside in external lamina; activated in damage or injury, proliferate, and replace damaged muscle cells
  37. skeletal muscle repair
    comes about as a result of disease (eg. muscular dystrophy) or damage (eg. small tears from excessive weight training)
  38. weight lifting causes ___________, not ________
    • weight lifting causes hypertrophy, not hyperplasia
    • you're increasing cells' SIZE, not their number
  39. 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
  40. smooth muscle repair
    actively proliferates in throughout life in response to damage or physiological needs (e.g. uterine expansion during pregnancy)
    • 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
    • dark horizontal lines (fascia adherens) & branching are clues that a slide = cardiac muscle
    • also centered nuclei/striations
    • in between spaces = endocardium
    • arrow = gap junction
    • horizontal squiggles = fascia adherens
    • cardiac muscle
    • 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

    • 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 Information

9 TOB Muscle
2016-09-15 15:55:23
TOB Exam2
MBS TOB Exam 2
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