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Histology - Exam 2 > Exam 2 - Muscle > Flashcards

Exam 2 - Muscle Flashcards

1
Q

epimysium

A

outermost layer of dense CT surrounding muscle

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2
Q

perimysium

A

CT surrounding muscle fascicles

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3
Q

contents of muscle fiber bundles

A

individual multinucleated muscle fibers/cells 10-100 um wide and up to 30 cm long

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4
Q

endomysium

A

basal lamina and reticular fibers that surround individual muscle cells - contains capillaries that supply blood to fibers

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5
Q

location of nuclei in skeletal muscle cells

A

in periphery just beneath sarcolemma

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6
Q

satellite cells

A

infrequent small stem cells found b/w the sarcolemma and basal lamina that may proliferate after trauma to form new myoblasts

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7
Q

triad system

A

T-tubules + sarcoplasmic reticulum; located at junction of A and I bands

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8
Q

T-tubules

A

infolding of plasma membrane, forms inner portion of triad

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9
Q

sarcoplasmic reticulum

A

modified sER, forms two side portions of triad

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10
Q

motor end plate

A

myoneural jxn - interaction site b/w nerve axon and muscle where basal lamina of axon and teloglia fuse w/ muscle fiber

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11
Q

changes in axon as it nears muscle cell

A

loses myelin sheath, but Schwann cells remain

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12
Q

teloglia

A

name for Schwann cells in the motor end plate region

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13
Q

what happens in synaptic cleft?

A

Ach from axon terminals diffuses across cleft and binds to Ach receptors located in junctional folds/subneural clefts of sarcolemma

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14
Q

number of muscle fibers innervated by one axon?

A

one or more

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15
Q

motor unit

A

a nerve and the muscles it innervates

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16
Q

botulism toxin

A

binds to presynaptic membrane, blocking Ach release

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17
Q

curare

A

paralytic drug that binds to Ach receptor

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18
Q

myasthenia gravis

A

autoantibodies against Ach receptors that block Ach binding and lead to progressive muscle weakness

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19
Q

mechanism of contraction

A

AP along sarcolemma-> T-tubules -> release Ca from terminal cisternae of SR -> Tn-c moves tropomyosin -> ATP on myosin hydrolyzed -> myosin binds actin -> Pi released -> head flexed -> ADP released -> actin pulled into A band -> new ATP binds myosin, releases myosin from actin

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20
Q

red fibers

A

type I fibers - slow twitch: high Mb, high mitochondria, fatigue resistant (stain strongly b/c mito enzymes)

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21
Q

white fibers

A

type II fibers - fast twitch: low Mb, low mitochondria, more stored glycogen, higher myosin-ATPase activity

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22
Q

intermediate fibers

A

characteristics b/w type I and II

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23
Q

control of fiber type differentiation

A

by innervation - red may become white by denervating and replacing with nerve from white fiber

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24
Q

muscle spindles

A

stretch receptors in perimysium that regulate muscle tone and tension - run parallel w/ main muscle and contain intrafusal fibers and neuron terminals in a fluid filled CT capsule

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25
muscle spindle nerve terminal discharge rate
discharge rate increases as the sensory ending is stretched
26
types of intrafusal fibers
nuclear bag (cluster of nuclei) or nuclear chain
27
types of spindle nerve terminal endings
- annulospiral (wind around intrafusal fibers) - flower spray (terminate in clusters) - Gamma-efferents/fusimotor (motor end plats formed near spindle poles)
28
induction of satellite cell proliferation
after muscle injury, myoD transcription factor and JGF (hepatocyte growth factor) induce proliferatoin of these cells
29
side-population cells
cells that can differentiate into all major blood cell lineages
30
where do you find side-population cells?
bone marrow and skeletal muscle
31
rigor mortis
death -> PM more permeable to Ca -> cross bridge attachment -> muscle fibers contract while Ach and ATP present -> once ATP used up, actin and myosin stay linked until decomposition
32
muscle atrophy
due to disuse - reduction in muscle fiber size, NOT number
33
myofilaments
make up myofibrils
34
thin myofilaments
actin, tropomyosin, troponin
35
thick myofilaments
myosin
36
A band
anisotropic band - thick and thin filaments, but only place thick filaments are found
37
I band
isotropic band - thin filaments only, bisected by Z disk where thin filaments attach
38
H band
contains myosin w/o heads and creatine kinase
39
creatine kinase
catalyzes ATP formation from ADP and phosphocreatine
40
M line
region of myomesin linking w/ myosin
41
Z disk
attachment point for thin filaments - contains alpha-actinin
42
sarcomere
functional unit of contraction
43
myofilament related structural proteins (7)
- titin - nebulin - alpha-actinin - myomesin - desmin - dystrophin - C protein
44
titin
elastic protein that connects myosin to Z disk - acts like spring to keep myosin filaments centered in sarcomere
45
nebulin
inelastic protein attached to Z disk that runs parallel to actin
46
myomesin
myosin binding protein that holds myosin filaments in register at M line
47
C protein
myosin binding protein similar to myomesin
48
alpha-actinin
bundles actin filaments into parallel arrays and anchors them to Z disk
49
desmin
intermediate filament that helps bind myofibrils to each other and encircles Z disk - linked to each other by plectin
50
dystrophin
actin binding protein that reinforces and stabilizes sarcolemma during contraction by linking cytoskeleton w/ ECM
51
actin
2 strings (F actin) of monomers (G actin) wrapped around each other in right-handed helix 7 nm in diameter
52
what regulates polymerization of actin in vivo?
thymosin B4 and profilin
53
what regulates actin filament length, stability/turnover?
cofilin, severin, gelsolin, villin, CapZ, gCAP39
54
tropomyosin
elongated protein dimer (35K MW) that lies in groove of actin helix and binds 3 troponin peptides
55
Tn-T
binds Tn complex to tropomyosin
56
Tn-I
inhibits binding of actin to myosin w/ help of tropomyosin
57
Tn-C
binds Ca, releasing Tn-I-tropomyosin inhibition of actin activation of myosin ATPase
58
alphabeta-crystallin
HSP that protects desmin from stress-induced damage
59
Duchenne's muscular dystrophy
X chromosome linked mutation in dystrophin gene that disrupts sarcolemma and Ca entrance into cell, resulting in muscle fiber necrosis
60
sarcoglycanopathies
limb-girdle muscular dystrophies with mutations in sarcoglycan genes - disrupts interactions w/ other proteins and association of sarcolemma with ECM
61
myosin
both a globular and fibrous structural protein w/ 2 heavy chains and 4 light chains
62
how many myosin molecules are thick filaments made of?
300-400
63
what does proteolytic digestion do to myosin molecules?
cleaves each heavy chain to produce a head and a tail
64
how many light chains does each head bind?
two light chains
65
heavy meromyosin
globular head of the heavy chain of myosin that contains an ATP and actin binding region
66
light meromyosin
rodlike alpha-helical tail of the heavy chain of myosin
67
cardiac muscle characteristics
banding, single nucleus/cell that is more centrally located, each fiber = many cells joined by intercalated discs, branched fibers
68
size of cardiac muscle cells
100-150 um long x 10-20 um wide
69
intercalated discs
transverse portion w/ fasciae adherens (actin filament anchor site) and macula adherens to bind adjacent cells together; lateral portion w/ gap junctions that ionically couple adjacent cells
70
how is cardiac muscle different from skeletal muscle?
- more mitochondria - more extrafibrillar sarcoplasm - larger T tubules - T tubules at Z disk - diads instead of triads - don't regenerate - intra and extracellular Ca - heals w/ fibrous CT that can block conduction
71
phospholamban
controls active transport of Ca into SR lumen
72
appearance of cardiocytes after MI
24 hrs: eosinophilic cytoplasm w/ some pyknotic nuclei | 3 days: inflammatory cells infiltrate tissue
73
smooth muscle
muscle under involuntary control of sympathetic or parasympathetic NS
74
smooth muscle cells
- spindle shaped - may branch - 20 um long - single central oval nucleus w/ 1 or more nucleoli -surrounded by basal lamina - caveolae on PM - cytoplasmic dense bodies w/ a-actinin (fxnal = of Z disk) - staggered arrangement of cells - no sarcomeres
75
what might smooth muscle cells secrete?
collagen and elastin
76
what does smooth muscle cytoplasm contain?
bundles of 5-7 nm thin filaments (actin, tropomyosin ONLY); 8-10 nm intermediate filaments (desmin, vimentin); 12-16 nm thick filaments (myosin)
77
myoepithelial cells of ectodermal origin
single, basket shaped smooth muscle cells found around sweat, salivary, lacrimal, and mammary glands
78
what attachments do myoepithelial cells contain?
hemidesmosomes
79
what do myoepithelial cells in mammary glands and lacrimal glands contract in response to, respectively?
oxytocin and Ach - to help dispel contents of glands
80
smooth muscle of mesodermal origin
located in respiratory, circulatory, digestive, reproductive tracts
81
smooth muscle of ectodermal origin
located in iris and ciliary body of eye
82
smooth muscle intermediate filament expression? why?
at high levels - serve as links in cytoskeletal network b/w dense bodies
83
smooth muscle myosin
2 heavy and 4 light chains, but filaments form only under certain conditions - dephosphorylation -> completely soluble
84
smooth muscle contraction
stim -> Ca increase in cytoplasm -> complex w/ calmodulin -> activate MLCK -> phosphorylate myosin -> myoson unfolds, forms filaments -> allows myosin to interact w/ actin
85
what other small molecule may also activate MLCK?
cAMP
86
how does estrogen influence smooth muscle?
increases cAMP -> contraction of smooth muscle
87
how does progesterone influence smooth muscle?
decreases cAMP -> relaxation of smooth muscle

Histology - Exam 2 (6 decks)

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