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Histology Exam 2 TonyFrim > Muscle > Flashcards

Muscle Flashcards

1
Q

epimysium

A

dense connective tissue that surrounds muscle

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2
Q

perimysium

A

surround muscle fiber bundles (fascicles)

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3
Q

muscle fiber bundles consist of…

A

individual multinucleate muscle fibers (cells)

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4
Q

surrounds muscle cells and contain capillaries that supply blood to muscle fiber (cell)

A

endomysium

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5
Q

what are the components of the endomysium?

A

basal lamina and reticular fibers

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6
Q

in a cross section where would you find nuclei in skeletal muscle?

A

nuclei lie in a peripheral location just beneath the sarcolemma

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7
Q

satellite cells

A

infrequent small cells found between the sarcolemma and basal lamina. Stem cells that may proliferate after trauma to form new myoblasts

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8
Q

muscle cells are the same as

A

muscle fibers

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9
Q

At the light microscope level, H and E stained muscle fibers have

A

dark A bands and light I bands.

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10
Q

functional unit of muscle contraction

A

sarcomere

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11
Q

skeletal muscle has a well developed _____ system

A

triad

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12
Q

The inner portion of skeletal muscle triad is…

A

an infolding of the plasma membrane (T-tubule)

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13
Q

The 2 side portions of skeletal muscle triad are

A

modified smooth endoplasmic reticulum (sarcoplasmic reticulum)

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14
Q

Where is the skeletal muscle T tubule system located?

A

at the junction of the A and I bands

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15
Q

interaction site between nerve axon and muscle

A

motor end plate (myoneural junction)

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16
Q

As axons get close to muscle cell, what happens to myelin sheath and Schwann cells?

A

axon loses myelin sheath near the muscle cell, but Schwann cells still cover the axon

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17
Q

interactions at the motor end plate

A

At the motor end plate the axon and Schwann cells basal lamina fuse with the muscle fiber

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18
Q

What are Schwann cells called in the region of the motor end plate?

A

teloglia

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19
Q

Axon terminals contain__________ which diffuses across synaptic cleft and binds ______________ located in the __________ ________ of the sarcolemma.

A

Axon terminals contain acetylcholine which diffuses across synaptic cleft and binds to Ach receptors located in the junctional folds of the sarcolemma.

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20
Q

Triad

A

T tubule flanked on both sides by dilations of sarcoplasmic reticule,

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21
Q

how many muscle fibers may a single axon innervate?

A

a single axon may innervate one or more muscle fibers

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22
Q

A nerve and the muscles it innervates is called a

A

motor unit

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23
Q

Myasthenia gravis

A

autoantibodies against acetylcholine receptors. Antibodies block acetylcholine which leads to progressive muscle weakness

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24
Q

Action potentials generated at the motor end plate is propagated along….

A

the sarcolemma and is carried into the myofibrils by the transverse T tubule system continuous with the myofibril sarcolemma

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25
Q

depolarization of the T tubule system causes

A

the release of Ca++ from the terminal cisternae of the sarcoplasmic reticulum

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26
Q

the release of Ca++ from the terminal cisternae of the sarcoplasmic reticulum causes…

A

conformational changes in molecules (troponin-C) that mediate the interaction of actin and myosin and results in muscle contraction

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27
Q

Red fibers

A

Type I, slow twitch. High myoglobin, numeRous mitochondRia, and fatigue Resistant

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28
Q

White fibers

A

Type II, fast twitch. Lower myoglobin and mitochondria than Red fibers. More stored glycogen. Higher myosin-ATPase activity than Type I

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29
Q

Intermediate fibers

A

characteristics between Type I and II

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30
Q

What controls fiber type differentiation?

A

innervation. a red fiber may be changed to a white fiber by denervating and replacing with nerve from white fiber

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31
Q

Stain strongly for mitochondrial enzymes i.e succinate dehydrogenase

A

Red fibers (Type I)

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32
Q

Where can you find muscle spindles?

A

muscle spindles run parallel with the main muscle fibers

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33
Q

Spindles sense…

A

Spindles sense changes in muscle length (stretch receptor)

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34
Q

contents within muscle spindle

A

contain modified muscle fibers (intrafusal fibers) and neuron terminals in a fluid filled connective tissue capsule

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35
Q

As the sensory ending is stretched the nerve terminal discharge rate increases or decreases?

A

increases

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36
Q

Nerve terminal has an _____________ ending

A

annulospiral (wraps around fiber in spiral configuration)

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37
Q

2 types of intrafusal fibers?

A

nuclear bag (cluster of nuclei) and nuclear chain

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38
Q

Muscle spindles may receive afferent sensory nerve fibers with what 3 types of endings?

A

1)annulospiral 2)flower spray 3)γ-efferents(fusimotor)

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39
Q

annulospiral nerve ending

A

wind around intrafusal fibers

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40
Q

flower spray nerve ending

A

terminate in clusters

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41
Q

γ-efferents (fusimotor)

A

motor end plates formed near spindle poles

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42
Q

After muscle injury, myoD and HGF induces

A

proliferation of satellite cells (quiescent myoblasts)

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43
Q

Rigor mortis

A

Upon death, muscle cell membranes become more permeable to Ca++. The Ca ions promote the cross-bridge attachment between actin and myosin. The muscle fibers contract while acetylcholine and ATP are present or until fully contracted. Muscles use ATP to pump calcium out of the cells and once the ATP is used up, the actin and myosin proteins will stay linked until decomposition

44
Q

muscle atrophy

A

atrophy due to disuse is caused by a reduction in muscle fiber size

45
Q

Does the number of muscle fibers change with muscle atrophy?

A

NO.NO.NO.

46
Q

4 main proteins found in myofilaments and associated size

A

actin(thin), tropomyosin(thin), troponin (thin), and myosin (thick)

47
Q

Myofibrils are composed of

A

myofilaments

48
Q

Z-disk

A

attachment point for thin filaments. Alpha actinin

49
Q

Z disk bisects

A

I band

50
Q

I band (isotopic band)

A

Thin myofilaments attach to Z disk and extend into A band

51
Q

Elastin protein that connects myosin to Z disc

A

Titin

52
Q

Inelastic protein attached to Z disc (runs parallel to actin)

A

Nebulin

53
Q

Desmin

A

intermediate filament that helps bind myofibrils to each other. Also encircles Z-disk

54
Q

What protein links Desmin to each other?

A

Plectin

55
Q

a filament of actin (F-actin) is made of

A

globular actin monomers (G-actin)

56
Q

Actin filaments are made up of __ strings of monomers wound around each other in a right handed helix

A

2

57
Q

Elongated protein dimer which lies in grooves of the actin helix

A

tropomyosin

58
Q

tropomyosin molecule binds these three troponin peptides

A

Tn-T, Tn-I, Tn-C

59
Q

Binds the Tn complex to tropomyosin

A

Tn-T

60
Q

this peptide in conjunction with tropomyosin inhibits the binding of actin to myosin

A

Tn-I

61
Q

Tn-C

A

calcium binding subunit- binding of Ca to this subunit releases the Tn-I tropomyosin inhibition of actin activation of myosin ATPase

62
Q

Desmin encircles the ______ of each sarcomere

A

Z-Disk

63
Q

______ links desmin together

A

Plectin

64
Q

Duchenne’s muscular dystrophy

A

X linked mutation in dystrophin gene

65
Q

Function of dystrophin

A

Dystrophin reinforces and stabilizes sarcolemma during contraction by linking the cytoskeleton with the ECM

66
Q

how does a lack of dystrophin impact muscle

A

defective or no dystrophin disrupts sarcolemma and Ca entrance into the cell = muscle fiber necrosis

67
Q

Sarcoglycanopathies

A

mutations in genes for sarcoglycans. disrupts interaction with other proteins and association of sarcolemma with ECM

68
Q

both a globular enzyme and a fibrous structural protein

A

myosin

69
Q

Basic components of a myosin molecule

A

2 identical heavy chains and 2 pairs of light chains

70
Q

Each myosin head binds how many molecules of light chains

A

Each myosin head binds 2 molecules of light chains

71
Q

Mechanism for muscle contraction

A

membrane depolarized and Ca released from the sarcoplasmic reticulum. Calcium ions then bind to the Tn-C subunit of troponin

72
Q

Ca ions binding to the Tn-C subunit of troponin results in

A

spatial configuration shift of troponin and moves the tropomyosin molecule deeper into the actin helix groove and exposes the myosin binding site on actin

73
Q

myosin binds to

A

actin

74
Q

when myosin head binds to actin- energy yielding breakdown of ATP to ADP + Pi ….

A

flexes the myosin head and the actin thin filaments are pulled into the A band

75
Q

Banding of cardiac muscle is similar to

A

skeletal muscle

76
Q

nucleus of cardiac muscle cells

A

single nucleus per cell, centrally located

77
Q

cardiac muscle fibers are composed of several cardiac muscle cells joined end to end by junctional zones called

A

intercalated disks

78
Q

transverse portion of intercalated disks contain

A

fasciae adherens (actin filaments anchor site) and macula adherens (desmosomes) to bind adjacent cells together

79
Q

lateral portion of intercalated disks have

A

gap junctions which ionically couple adjacent cells

80
Q

cardiac muscle in relation to skeletal muscle

A

cardiac muscle has more mitochondria and extra fibrillar sarcoplasm than skeletal muscle. Larger T tubules in cardiac. triads are less common in cardiac muscle

81
Q

how does cardiac muscle respond to injury

A

cardiac muscle responds to injury by forming a fibrous connective tissue scar.

82
Q

how does cardiac muscle make new cells

A

under normal circumstances cardiac muscle does not regenerate

83
Q

Phospholamban

A

controls active transport of Ca++ into sarcoplasmic reticulum lumen.

84
Q

amount and activity of phospholamban is controlled by what hormone

A

thyroid hormone

85
Q

how is smooth muscle controlled?

A

smooth muscle is under involuntary control of sympathetic or parasympathetic nervous system

86
Q

appearance of smooth muscle cells

A

spindle shaped, but may branch. single central oval nucleus with one or more nucleoli. surround by a basal lamina

87
Q

smooth muscle cells may secrete

A

collagen and elastin

88
Q

2 smooth muscle cells may form

A

gap junctions and interdigitations that facilitate electrical conduction

89
Q

Plasma membrane on smooth muscle cells has numerous _______ on the surface and cytoplasmic _______ ______ that contain alpha actinin

A

caveolae

dense bodies

90
Q

arranged of cells in smooth muscles can be described as

A

“staggered”

91
Q

single smooth muscle cells can be found

A

around sweat, salivary, lacrimal, and mammary glands

92
Q

mammary glands contract in response to

A

oxytocin

93
Q

lacrimal glands contract in response to

A

acetylcholine

94
Q

smooth muscle of mesodermal origin can be found in what body systems/areas

A

respiratory, circulatory, digestive and reproductive tracts

95
Q

smooth muscle of ectodermal origin can be found…

A

in the iris and ciliary body of the eye

96
Q

smooth muscle does not contain

A

sarcomeres

97
Q

If smooth muscle is dephosphorylated

A

completely soluble

98
Q

Components of smooth muscle myosin (chains)

A

smooth muscle has 2 heavy chains and 4 light chains like striated muscle

99
Q

when smooth muscle is stimulated, Ca++ increases in cytoplasm and complexes with

A

calmodulin (Ca++ binding protein)

100
Q

the Ca++-calmodulin complex activates

A

myosin light chain kinase

101
Q

myosin light chain kinase phosphorylates myosin which causes

A

myosin to unfold and form filaments and this allows myosin to interact with actin

102
Q

other than Ca-calmoduin complex what else may activate myosin light chain kinase

A

cAMP

103
Q

H band contains

A

myosin (no heads) and creatine kinase

104
Q

creatine kinase, which is located in the H band, catalyzes

A

ATP formation from ADP and phosphocreatine

105
Q

A band

A

(anisotropic band)- thick myofilaments found only A band + thin myofilaments

Histology Exam 2 TonyFrim (6 decks)

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