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Structures: Part Deux > LEC43: Muscle Tissue > Flashcards

LEC43: Muscle Tissue Flashcards

1
Q

3 types of muscle tissue

A

smooth, skeletal, cardiac

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2
Q

general functions of muscle tissue

A

1) movement
2) maintenance of posture
3) joint stabilization
4) heat generation

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3
Q

special functional characteristics of muscle

A

1) contractility
2) excitability
3) extensibility
4) elasticity

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4
Q

contractility means

A

muscle only has 1 action: to shorten

shortening generates pulling force

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5
Q

excitability means

A

muscle can be excited; nerve fibers cause electrical impulse to travel

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6
Q

extensibility means

A

muscle can stretch w/ contraction of an opposing muscle

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7
Q

elasticity means

A

muscle recoils passively after being stretched

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8
Q

skeletal muscle location

A

attach to, move skeleton

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9
Q

how much of body weight does skeletal muscle comprise?

A

40%

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10
Q

are skeletal muscle contractions voluntary or involuntary?

A

voluntary

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11
Q

which muscle types are striated?

A

skeletal, cardiac

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12
Q

where is cardiac muscle found?

A

only in wall of the heart

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13
Q

are cardiac muscle contractions voluntary or involuntary?

A

involuntary

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14
Q

where is smooth muscle found?

A

walls of hollow organs

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15
Q

are smooth muscle contractions voluntary or involuntary?

A

involuntary

..although some voluntary as well

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16
Q

what does each skeletal muscle have associated w/ it?

A

1 nerve, 1 artery, 1 vein, which branch repeatedly

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17
Q

what do skeletal muscles connect

A

1 bone to another

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18
Q

what do skeletal muscles span

A

at least 1 movable joint, but can span 2 or more joints

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19
Q

where is skeletal muscle origin/insertion re: movement?

A

origin: the less movable attachment
insertion: pulled toward the origin

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20
Q

do both bones move when skeletal muscle contracts?

A

no, usually 1 bone moves other remains fixed

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21
Q

where is origin re: insertion (proximal, distal)

A

origin is proximal to insertion

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22
Q

what is biarticular muscle?

A

multijoint muscle, when muscles span 2 or more joints, cause movements at 2 joints

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23
Q

what are “fleshy” attachments?

A

aka direct attachment

attachment so short muscle appears to attach directly to bone

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24
Q

what is indirect attachment?

A

when connective tissue extends well beyond the muscle

eg: tendon

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25
Q

what do most skeletal muscles have attached to them?

A

tendonous attachment - cordlike

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26
Q

characteristics of skeletal muscle

A

1) moves skeleton
2) voluntary/conscious control
3) limited regeneration

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27
Q

muscle cell plasma membrane?

A

sarcolema / plasmalemma

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28
Q

muscle cell ER?

A

sarcoplasmic reticulum

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29
Q

muscle cell cytoplasm?

A

sarcoplasm

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30
Q

what comprises a skeletal muscle’s motor unit?

A

1 motor nerve + all the muscle fibers it innervates

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31
Q

how many fibers in a muscle cell?

A

1

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32
Q

how is skeletal muscle nucleus?

A

multinucleated, nuclei are peripherally located, surrounded by endomysium

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33
Q

arrangement of skeletal muscle fiber

A

fiber surrounded by endomysium

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34
Q

how are skeletal muscle fibers bundled?

A

fibers grouped into fasicles; surrounded by perimysium

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35
Q

how are several skeletal muscle fasicles grouped?

A

bundles of fasicles make up a muscle, surrounded by epimysium

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36
Q

what are endomysium, perimysium, epimysium made of?

A

connective tissue

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37
Q

what is a muscle cell made of?

A

many myofibrils

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38
Q

what are myofibrils made of?

A

bundles of myofilaments (thin-actin, thick-myosin), organized into sarcomeres

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39
Q

which tissue types are present in a skeletal muscle

A

all!

  • arteries/veins have endothelial cell lining
  • nerves have nervous tissue
  • CT surrounds muscle cell fibers
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40
Q

what is connective tissue function re: skeletal muscle?

A

necessary for muscle function, continuous with tendons, muscle attachments distributing force of muscle to bone, skin, etc

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41
Q

what surrounds myofibril?

A

sarcoplasmic reticulum

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42
Q

what are A and I bands named for?

A

how they rotate polarized light
I: isotropic: same in all drxns
A: anisotropic: diff in all drxns

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43
Q

sarcomere

A

basic unit of a muscle/myofiber, what allows us to flex

segment between 2 neighboring Z lines

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44
Q

subdivisions of sarcomere?

A

A band, I band, Z line, H band, M line

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45
Q

A band?

A

dark band

actin, myosin filaments

46
Q

I band?

A

light band

only actin

47
Q

Z line?

A

bisects I band

anchors actin, defines border of adjacent sarcomeres

48
Q

H band?

A

light band, bisects A band

only myosin

49
Q

M line?

A

dark line, bisects H band

anchors myosin

50
Q

what type of filaments make up myofibrils?

A

1) thick-myosin
2) thin-actin
3) elastic-titin

51
Q

structure of myosin

A

2 light chains + ATPase domain + actin-binding domain

52
Q

how does myosin filament assemble? what is rod structure?

A

self-assembles into a-helical tail, large bipolar aggregate or filament

53
Q

what does troponin connect? what is troponin complex made of?

A

connects to actin a-helices, to tropomyosin between actin filaments

1) calcium binding part
2) inhibitory part-troponin I
3) troponin T, binds to tropomyosin

54
Q

what covers actin’s myosin-binding site?

A

tropomyosin

55
Q

what is driving force for movement in myosin?

A

myosin II heads, thru ATPase activity move along actin filament

56
Q

what connects actin to Z disc?

A

a-actinin

57
Q

what connects myosin to Z disc?

A

titin

58
Q

where is a-actinin?

A

incorporated into Z disk

attaches actin to the disk

59
Q

what is sarcoplasmic reticulum made of?

A

smooth ER

60
Q

sarcoplasmic reticulum function?

A

store Ca++, release it when muscle stimulated to contract

61
Q

what is continuous with sarcolemma? what is the result?

A

t-tubules

therefore whole muscle contracts simultaneously (including deep parts)

62
Q

what are terminal cisternae

A

cross-channels in sarcoplasmic reticulum

63
Q

what makes troponins change conformation?

A

high [Ca++]

64
Q

what binds to troponin in muscle contraction? what is result?

A

Ca++ binds
Ca++ moves tropomyosin out of the way, bonds to troponin
allows myosin to bind to actin, muscle contraction

65
Q

what happens if [Ca++] is low?

A

troponin returns to standard conformation
tropomyosin blocks myosin
no muscle contraction

66
Q

role of neurotransmitters in muscle contraction, re: calcium?

A

1) neurotransmitters from motor end plate cause depolarization of sarcollema, including T-tubules
2) depolarization extends to membranes of sarcoplasmic reticulum
3) Ca++ released into sarcoplasm

67
Q

what happens when Ca++ in sarcoplasm?

A

binds to Tpn C, separates Tpn I from actin, exposes myosin binding site, contraction cycle begins

68
Q

what surrounds T tubule and skeletal muscle?

A

2 terminal cisternae

69
Q

what makes up the “triad” of the sarcoplasm? where is it?

A

2 terminal cisternea + T tubule

at the A-I junction

70
Q

what is the nature of the “triad” in cardiac muscle?

A

it is a diad

71
Q

motor end-plate function?

A

motor end plate of neuromuscular junction impinges on muscle fiber

72
Q

what happens to A-I band length when muscle contracts?

A

it shortens

73
Q

what kind of movement when actin-myosin bind?

A

RATCHET

74
Q

cause of contraction of muscle fiber?

A

1) Ca++ influx

2) ATP hydrolyzed to ADP + Pi

75
Q

role of satellite cell in skeletal muscle?

A

lie within basal lamina

migrate up, make filaments to fill in damaged areas when skeletal muscle damaged

76
Q

what is myasthenia gravis?

A

autoimmune disease

antibodies against Ach receptor bind to receptor, prevent Ach from binding to it, blocks normal nerve-muscle interaction, no muscle firing

clinically, ppl suffer from progressive muscular weakness

77
Q

how are the fibers in cardiac muscle?

A

fibers branch

78
Q

position of nucleus in cardiac muscle?

A

1-2 central nuclei

79
Q

do cardiac muscles have satellite cells?

A

no

80
Q

what are features within cardiac muscles?

A

1) intercalated disks
2) T-tubules at Z lines
3) cross-striations

81
Q

how many cells make up a cadiac muscle?

A

many cells/muscle

82
Q

where do cardiac muscle cells join

A

interalated disc

83
Q

what is a cardiac muscle “fiber”

A

long row of joined cardiac muscle cells

84
Q

what is myocardium

A

thick bundles of cardiac muscle

85
Q

what is inherent rhythmicity?

A

characteristic of cardiac muscle whereby each muscle cell beats separately, without stimulation

86
Q

syncitium

A

cardiac muscle cells are interconnected by specialized membranes with gap junctions which are synchronized electrically in an action potential

87
Q

how is terminal cisternae arrangement in cardiac muscle?

A

diad of terminal cisternae join with T tubule at Z line

88
Q

how does intercalated disc join together cardiac muscle cells?

A

1) macula adherens
2) gap junction
3) fascia adherens

89
Q

6 major locations of smooth muscle

A

1) inside eye
2) walls of vessels
3) respiratory tubes
4) digestive tubes
5) urinary organs
6) reproductive organs

90
Q

shape of smooth muscle cells?

A

spindle-shaped

91
Q

how many nuclei in smooth muscle cell?

A

1

92
Q

how are smooth muscle cells grouped?

A

into sheets; often run perpendicular to each other

93
Q

how do smooth muscles move?

A

slow, sustained contractions that’re resistant to fatigue

94
Q

which type of muscles do peristalsis?

A

smooth muscle

95
Q

what stimulates smooth muscle to contract?

A

can be stretching, hormones; doesn’t have to be nervous signal

96
Q

where is myenteric plexus, what kinds of cells found there?

A

GI

neuronal ganglion cells

97
Q

what feature of smooth muscle takes in calcium?

A

surface caveolae, endocytotic vesicles

98
Q

what does calcium bind w/ in smooth muscle?

A

calmodulin

99
Q

how does smooth muscle contraction cascade work?

A

Ca-calmodulin complexes > phosphorylation of myosin light chain kinase of myosin rod > conformational change exposing actin binding site of myosin > myosin binds actin > contraction

100
Q

what are dense bodies?

A

analogous to z-disks, but in smooth muscle

101
Q

where are dense bodies?

A

in smooth muscle

beneath plasma membrane, in cytoplasm’s intercytoplasmic surface

102
Q

what do dense bodies contain?

A

alpha actinin site of insertion of actin filaments - holds actin in place

103
Q

does smooth muscle have myosin filaments?

A

yes!

104
Q

what must occur for myosin to be able to bind actin?

A

myosin light chain kinase phosphorylates light chains; tail extends; forms bipolar myosin filaments, myosin heads can now bind actin

105
Q

which muscle tissue type cannot regenerate in adults?

A

cardiac muscle

106
Q

can skeletal muscle tissue regenerate?

A

nuclei cannot undergo mitosis; tissue can undergo limited regeneration

107
Q

what in skeletal muscle allows regeneration?

A

satellite cells

108
Q

can smooth muscle tissue regenerate?

A

yes!

i.e. uterus enlarges during pregnancy

109
Q

how many known actin genes?

A

at least 4

1) cardiac actin
2) skeletal muscle actin
3) vascular smooth muscle actin
4) visceral smooth muscle actin

110
Q

what causes myopathies

A

changes in actin gene structure

111
Q

how to distinguish myopathy from neuropathy?

A

histology

Structures: Part Deux (36 decks)

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