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Muscle tissue Flashcards

1
Q

What is the primary protein in thin myofilaments?

A

Actin

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2
Q

What are the two types of myofilaments?

A

Thin and thick filaments

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3
Q

The interaction of the thin and thick filaments in muscles does what?

A

Produces movement

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4
Q

What is a sarcomere?

A

A contractile unit of striated muscle

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5
Q

What is G actin and F actin?

A

G actin is the monomer of actin that is globular. These assemble into chains, with two chains twisting about each other to produce the F-actin

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6
Q

What are the three components of thin myofilaments?

A

Actin
Troponin
Tropomyosin

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7
Q

What are the three types of troponin, and what is the function of each?

A

TnT - subunit that attaches to tropomyosin

TnC - subunit that binds to Ca

TnI - subunit that binds troponin actin and inhibits it

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8
Q

What is the structure of tropomyosin?

A

2 polypeptide chains that form an alpha helix

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9
Q

What is the function of tropomyosin?

A

Each tropomyosin molecule (alpha-helix) rests on 7, G-actin molecules and covers their active sites (for myosin).

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10
Q

What is the combined function of troponin and tropomyosin?

A

To block actin

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11
Q

How many actin molecules does tropomyosin rest on? What is it doing there?

A

7–blocks active sites of actin

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12
Q

What is the primary protein of a myosin filament?

A

Myosin II

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13
Q

What does the myosin molecule consist of?

A

2 heavy chains, and 4 light chains

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14
Q

What are the two segments of meromyosin?

A

Heavy and light meromyosin

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15
Q

What does the heavy meromyosin consist of?

A

4 light chains
2 globular heads
A short, twisted tail

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16
Q

What does the light meromyosin consist of?

A

2 chains wrapped around each other in an alpha helix

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17
Q

What is the function of adding trypsin to myosin?

A

breaks down into meromyosin

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18
Q

What is the fuction of adding trypsin and papain to myosin?

A

breaks down into meromyosin as well as the S1 and S2 chains

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19
Q

What does the S1 moiety of myosin consist of?

A

2 light chains and 1 globular head

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20
Q

What does the S2 moiety of myosin consist of?

A

the short, twisted tail

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21
Q

What is the contractile unit of a muscle cell?

A

Sacromeres

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22
Q

What are the structures that contain multiple sarcomeres and extend the length of the cell?

A

Myofibrils

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23
Q

Many myofibrils runing parallel to each other form what structure?

A

a muscle fiber

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24
Q

What is the 3D shape of a sarcomere?

A

Cylinder

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25
Q

What is the disk that separates each cylindrical unit of a sarcomere? What does this area function as?

A

Z disk

Functions as an attachment of thin filaments via alpha actinin

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26
Q

What is the function of alpha actinin on the z band?

A

Anchors thin filaments

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27
Q

What is in the H band of a sarcomere?

A

Only thick filaments

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28
Q

What is in the I band of a sarcomere?

A

Only thin filaments in adjacent sarcomeres

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29
Q

True or false: the H band is a subset of the A band

A

True

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30
Q

What is the M line of a sarcomere? What is the major protein here?

A

Consists of protein structures lying between thick filaments, holding them in register.

Creatine kinase is the major protein here

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31
Q

What are the proteins that anchors thin filaments to the Z disk?

A

Alpha actinin and nebulin (x2)

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32
Q

What is the protein that anchors the thick filaments to the Z disk?

A

4 titin molecules

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33
Q

What is nebulin?

A

Inelastic protein that wraps around thin filaments and anchors it to the Z disk

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34
Q

What are the proteins that secures thick filaments in register at the M line?

A

Myomesin and C protein

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35
Q

What is the cytoplasmic protein that binds actin filaments to laminin?

A

Dystrophin

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36
Q

What are the components of muscles cells that are specific to muscles cells?

A 
Sarcolemma
Sarcoplasm
Sarcosomes
myofibrils
Sarcoplasmic reticulum
myoglobin
Glycogen
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37
Q

What is the sarcolemma?

A

cell membrane + exernal lamina +reticular fibers

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38
Q

What is the sarcoplasm

A

Muscle cell cytoplasm

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39
Q

What are sarcosomes?

A

muscle cell mitochondria

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40
Q

What are myofibrils?

A

long, cylindrical chains of sarcomeres

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41
Q

What is the sarcoplasmic reticulum?

A

sER of muscle cells

42
Q

What is the endomysium?

A

a layer of reticular fibers that surrounds each muscle cell

43
Q

What is the perimysium?

A

a thin, collagenous connective tissue, derived from the epimysium, and surrounds fascicles of muscles

44
Q

What is the epimysium?

A

Dense, irregular collagenous tissue that surrounds bunches of fascicles (deep fascia)

45
Q

Deep fascia in anatomy = what in histology?

46
Q

Nerves and vessels from the epimysium travel through what layer of the muscle to end up n each muscle cell?

A

The perimysium

47
Q

Where do the nuclei sit in muscle cells? How many are there per muscle cell?

A

Multiple nuclei per cell, which sit at the sarcolemma (plasma membrane)

48
Q

Are muscle cell nuceli euchromatic or heterochromatic? What shape are they?

A

Euchromatic

oval shaped

49
Q

What is the ECM that sits just outside the sarcolemme? What type of fibers are in this area?

A

External lamina filled with reticular fibers

50
Q

Can you see the A or Z band at the LM level?

51
Q

What are the transverse tubules? What are their function?

A

Invaginations of the cell membrane (sarcolemma).

Their lumen is continuous with the extracellular space, and contain extracellular fluid.

Their function is to carry nerve impulses deep into the cell

52
Q

Where is the sarcoplasmic reticulum found?

A

Form a “lacy” sleeve around each myofibril

53
Q

Nerve cell impluses travel through what to reach myofibrils?

A

The T tubules

54
Q

What are terminal cisternae?

A

Terminal part of T tubules that end on the sarcoplasmic reticulum, and hold Ca

55
Q

What is a triad (in terms of muscle cells)? Where are these found?

A

1 T tubule + 2 terminal cisternae. Found at the A-I junction of a sarcomere

56
Q

What are the regenerative cells that lie between the skeletal muscle cell and its external lamina? What are their function?

A

Satellite cells

They proliferate when the tissue is injured to form new myoblasts

57
Q

What must be present in order for new myotubes to form from satellite cells? What happens if this is not present?

A

The external lamina

If this is not present, scar tissue forms from fibroblasts instead

58
Q

What is a motor unit?

A

A lower motor neuron and all of the muscle fibers it innervates

59
Q

What is the neuromuscluar junction?

A

The synapse of the motor neuron and its muscle

60
Q

What is the neurotransmitter that the axon terminals contain?

A

Acetylcholine

61
Q

What does a motor end plate consist of?

A

Axon terminal, synaptic cleft and the muscle cell sarcolemma

62
Q

What is myasthenia gravis?

A

Autoimmune disease where acetylcholine receptors are attacked by antibodies. Causes progressive weakness d/t receptor destruction.

63
Q

What is Duchenne muscular dystrophy (DMD)?

A

X-linked recessive disease that has a mutation of dystrophin

64
Q

What is the function of dystrophin

A

Protein that connects actin filament near the Z discs to the laminin in the ECM

65
Q

Histologically, what are the differences between cardiac and skeletal muscles?

A

Cardiac muscles are shorter than skeletal muscles, are branched, and contain many more capillaries in the surrounding spaces

66
Q

True or false: cardiac muscles contain glycogen and lipid droplets

67
Q

Do cardiac muscles have stronger or weaker striations than skeletal muscles?

68
Q

How many nuclei do cardiac muscles have? Where are they located within the cell?

A

1-2, centrally located

69
Q

What are atrial granules? Where are they found

A

Granules that contain atrial natriuretic factor and BNP (diauretics), usually found in the right atrium

70
Q

What are intercalated discs? What type of muscles are these specific to?

A

Specialized intercellular junctions between cardiac muscles

71
Q

What does the transverse portion of the intercalated disc do (3)?

A
  1. Anchors actin filaments of terminal sarcomere to plasma membrane
  2. transmits contractile forces from cell-cell
  3. binds cells together via desmosomes
72
Q

What does the lateral portion of the intercalated discs do?

A

Has gap junctions that permit the flow of ions from cell to cell so cardiac muscles contract together

73
Q

Do purkinje fibers tend to stain darker or paler than other muscle cells? What do they contain?

A

Paler

Glycogen and few myofilaments

74
Q

What is the function of the Purkinje fibers?

A

To relay electrical impulses to cardiac muscle fibers

75
Q

What are the three structures that form the heart’s intrinsic conducting system?

A

AV node
SA node
Purkinje fibers

76
Q

What percent of cardiac muscles cells volume is occupied by mitochondria?

77
Q

What is abundant in cardiac muscle cells?

78
Q

Injury to the heart muscle is repaired with what type of tissue?

A

Fibrous connective tissue

79
Q

What are the three layers of the heart?

A

Endocardium
Myocardium
Epicardium

80
Q

What layer of the heart are Perkinje fibers located in?

A

Endocardium

81
Q

What type of structure do smooth muscle cells form?

82
Q

Where is smooth muscle found?

A

Pharynx, esophagus, stomach, small intestine, large intestine, vessel walls, jrespiratory tract

83
Q

What do smooth muscle cells lack that are skeletal muscle cells have?

A

Striations

84
Q

What proteins do smooth muscle cells have?

A

Myosin and actin, but NO troponin

85
Q

How many nuclei are in smooth muscle cells?

A

Only one (mononuclear)

86
Q

What is the shape of smooth muscle cells?

87
Q

Are the nuclei of smooth muscle cells euchromatic or heterochromatic?

A

Euchromatic

88
Q

Where are the nuclei of smooth muscle cells?

A

Center of the cell

89
Q

How much space is between smooth muscle cells? Skeletal? Cardiac?

A

None in smooth

Present in cardiac and skeletal

90
Q

Looking at a EM slide of smooth muscle cells, you see small bubbles near the border of the cell. What are these?

A

Caveolae -coated vesicles containing Ca

91
Q

What are caveolae?

A

Pinocytotic vesciles in smooth muscles that release Ca into the cell for contraction

92
Q

What criss-crosses the smooth muscle cells?

A

Myofilaments

93
Q

What are dense bodies?

A

Connections of myofilaments either:

  1. on the cell membrane
  2. Cytoplasmic at myofilament bundles located in the cytoplasm
94
Q

What is the function of dense bodies on the cell membrane of smooth muscle cells?

A

Contract the cell and cause a puckering

95
Q

Ca released from the sarcoplasmic reticulum of muscle cells binds where?

A

To the Troponin I complex

96
Q

What happens to the confomation of the actin filament when Ca binds?

A

Changes conformation, and exposes myosin binding site on actin

97
Q

What happens to the distance between Z disks during contraction?

A

Get closer

98
Q

What happens to the free end of the actin molecule in contraction?

A

Get closer to the A band

99
Q

What happens to the length of the thin filaments during contraction? Thick?

A

They both remain the same

100
Q

What happens to the width of the A band during contraction?

A

Stays the same

101
Q

What happens to the width of the I band during contraction?

A

Gets narrow

102
Q

What happens to the width of the H band during contraction?

A

Disappears

Cell and tissue (45 decks)

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