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Block 3 Found Sci > 1-Striated Muscle Skeletal > Flashcards

1-Striated Muscle Skeletal Flashcards

1
Q

basal lamina

purpose

A

important structural element serves as anchor point for proteins than span cell membrane

link endomysium to sarcolemma

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2
Q

T-tubules

definition

A

specialized invaginations in muscle cell membrane conduct AP (depolarization) from cell surface to calcium reservoir (@sarcoplasmic reticulum)

SR surrounds myofilaments

membrane = sarcolemma

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3
Q

muscle development sequence

skeletal muscle

A
  1. pluripotent stem cells diff to myogenic progenitor cells
  2. myoblasts
  3. committed myocytes OR dormant satellite cells to be acitvated later
  4. myocytes aggregate into myotubes
  5. mature fiber w/ nuclei @ periphery
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4
Q

mature muscle organization

A
  1. myofilaments
  2. myofibrils
  3. muscle fiber
  4. muscle fascicle
  5. muscle
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5
Q

layers of CT

A
  1. endomysium: around indiv muscle cells/fibers
  2. perimysium: divides into bundles aka surrounds fascicles
  3. epimysium: attachs directly to bone or tendon aka surrounds entire muscle group
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6
Q

basal lamina/BM composition

A

collagen + proteoglycans + glycoproteins/complex polysaccharides

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7
Q

terminal cisternae of SR

A

swelling at end of reticular network of sarcoplasmic reticulum where Ca stored

2 terminal cisternae + T tubule = triad

SR surrounds fibrils

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8
Q

contractile elements

sarcomere

A
  1. thin filaments (actin)
  2. thick filaments (myosin)
  3. titin
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9
Q

structural elements

A
  1. Z disc (est boundaries of sarcomeres)
  2. M line (center line)
  3. Titin
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10
Q

bands/zones

sarcomere

A
  1. I band (light color) = thin filaments only
  2. A band (dark color, wider) = thin + thick
  3. H zone (middle of A) = thick only
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11
Q

thick filaments

A

bipolar (head and tails, tails medial) structure of a lot of myosin molecules

filaments wrap together in quasi helical fashion

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12
Q

myosin molecule

A

2 heavy chains in alpha-helix + 2 light chains (regulatory and essential) per chain so 4 total

neck of chain allows for hinge to articulate with thin filaments

myosin head has ATPase activity

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13
Q

thin filaments

A

double strand of G actin sub units twisted a helix

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14
Q

regulatory proteins with thin filaments

A
  1. tropomyosin
  2. troponins
    T = bind tropomyosin
    C = bind calcium
    I = inhibitory, changes conformation when C binds Ca and moves T so tropomyosin out of active site on actin
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15
Q

titin

A

gigantic muscle protein that anchors thick filaments to Z discs, spans 1/2 sarcomere

gives structural integrity/elastic stabilization of thick/thin filaments, passive tension

bi-directional spring to help sarcomere return to og

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16
Q

Z disc/Z line

A

lattice like structural element at both ends of sarcomere

anchor point for thin filaments and titin filaments

connect to Z discs of adjacent myofibrils by intermediate filaments (desmin)

17
Q

M line/M disc

A

lattice like structural element at center of sarcomere

anchor for thick filaments and titin
-M protein: stabilized proteins in M line
-obscurin: regulate sarcomere/SR interaction
-myomesin: anchors myosin with titin

18
Q

costameric protein complex

A

aka dystrophin-glycoprotein complex + integrins = costamere

stabilizes muscle cell membrane during contraction

scaffolding for myofibrils by linking cytoskeleton w/ ECM and anchors Z disk (w/ contracticle proteins) to basal lamina

19
Q

outcomes of disease

clinical relevance

A
  1. respiratory insufficiency/failure
  2. inc suscept to respiratory infection
  3. spinal curvature
  4. cardiomyopathy
  5. metabolic abnormalities
  6. reduced mobility/independence
20
Q

muscular dystrophy

A

mutations in genes that encode dystrophin or other components of costamere

results: disorganized costameres
enhanced membrane leak
edema/inapp cytosolic Ca generation
ECM deposition

21
Q

duchenne muscular dystrophy

A

no dystophin protein present

fatal by age 30 via cardio respiratory failure

22
Q

becker muscular dystrophy

A

dystrophin present but reduced in amount

less serious, usually not fatal

23
Q

limb girgle dystrophy

A

mutations for sarcoglycans or other dystrophin-glycoprotein complex

24
Q

motor unit

A

one motor neuron and all the muscle fibers that it innervates

25
Q

neurotransmission at triad

A
  1. depolarization down t tubule
  2. conformation change in L type Ca channel (LTCC)
  3. 4 LTCC attach to 4 RYR = tetrad, opens
  4. termination when Ca sequestered in myoplasm
26
Q

Ca reuptake mechanism

A

SERCA major way, ATP dependent

Calreticulin and Calsequestrin are SR proteins that bind Ca+

27
Q

sliding filament theory

A

thin filaments slide over thick filaments bc thick pull toward center of sarcomere

thin pull Z discs toward each other and sarcomere shortens

28
Q

thin filament regulation

A

Ca triggers contraction by interacting with troponin C = conformational change

tropomyosin shifted deeper into actin groove to expose active site for myosin from thick to bind

29
Q

cross bridge cycle

A
  1. ATP binds to myosin
  2. dissociation of AM complex
  3. ATP hydrolyzed = conform change aka cocked state
  4. cross bridge formed when active site exposed
  5. Pi released = conform change and power stroke
  6. ADP released and cross bridge detach from myosin if ATP present
30
Q

magnesium

EC coupling

A

co factor for myosin ATPase mediated ATP hydrolysis

deficiency can cause muscle weakness and cramping, common in GI disease, diabetes, alcoholism, aging

31
Q

modulating force

A
  1. recruit more and bigger motor units if inc stimulus intensity
  2. frequency summation aka high frequency stimulation = repeated contractions of progressively greater force until reaches sustained maximal force production (fused tetanus)

progressive inc in myoplasmic Ca w/ each stimuli until max Ca levels reached

32
Q

type I slow twitch fibers

A

-aerobic pathway for ATP
-resistant to fatigue
-low/slow force output

similar to cardiac muscle with diff myosin isoforms

33
Q

type II fast oxidative fibers

A

aerobic or anaerobic ATP
resistant to fatigue
moderate/rapid force output

34
Q

type II fast glycolytic

A

anaerobic pathway for ATP
fatigue quickly
high/rapid force output

Block 3 Found Sci (60 decks)

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