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ANA300 > MUSCLE > Flashcards

MUSCLE Flashcards

1
Q

in muscle contraction, what decreases (SFT)

A

sarcomere length (Z-Z)
H zone
I band

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2
Q

in muscle contraction, what remains constant (SFT)

A

A band (length of thick filaments)

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3
Q

in muscle contraction, what increases (SFT)

A

zone of overlap

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4
Q

what is the “super power” of muscle

A

ability to contract => tension

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5
Q

3 types of muscle and their classifications

A

skeletal (voluntary, striated)
cardiac (involuntary, striated)
smooth (involuntary, non striated)

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6
Q

what allows voluntary muscle to contract

A

neural input

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7
Q

what happens if involuntary muscle is denervated

A

can still contract; neves only regulate, don’t initiate contraction

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8
Q

3 layers of CT in muscle

A

epimysium (entire muscle)
perimysium (fascicle)
endomysium (muscle fibre/cell)

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9
Q

another name for muscle cell

A

muscle fibre

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10
Q

name of proteins within sarcoplasm

A

myofibrils

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11
Q

Sharpey’s fibres

A

collagen fibres of tendon continuous with collagen fibres of periosteum

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12
Q

T or F: neuromuscular bundles perforate CT layers of muscle

A

T; pierce CT covering then branch to reach ind’l muscle fibres

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13
Q

how many nuclei in muscle fibre

A

multinucleate (>100/fibre)

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14
Q

how do muscle fibres develop

A

fusion of myoblasts (mesodermal cells)

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15
Q

function of myosatellite cells

A

limited repair of skeletal muscle (normally, damaged -> replaced with fibrous CT)

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16
Q

how long can 1 muscle cell be

A

> 1m (skeletal muscle fibre)

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17
Q

what cell-cell junctions exist in skeletal muscle

A

none; fibres arranged in parallel; surrounded by endomysium

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18
Q

where are nuclei in skeletal muscle fibres

A

squeezed to periphery

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19
Q

what ensures that skeletal fibres contract together

A

endomysium transfers tension

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20
Q

sarcoplasm

A

muscle fibre cytoplasm

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21
Q

sarcolemma

A

muscle fibre cell membrane

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22
Q

transverse tubules

A

tubular extensions of sarcolemma; perpendicular to surface

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23
Q

sarcoplasmic reticulum

A

ER of skeletal muscle fibre

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24
Q

terminal cisterna

A

expanded sarcoplasm reticulum on either side of T tubule

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25
Q

triad in skeletal muscle

A

t tubule with adjacent terminal cisterna

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26
Q

bundles of myofilaments

A

myofibrils

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27
Q

2 types of myofilaments

A

actin (thin), myosin (thick)

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28
Q

what feature => striations

A

sarcomeres

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29
Q

how long are myofibrils relative to cell

A

length of whole cell

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30
Q

2 types of actin

A 
G actin (globular subunit)
F actin (filamentous; 300-400 G actin)
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31
Q

what covers actin binding sites

A

tropomyosin

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32
Q

what holds tropomyosin in place

A

troponin

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33
Q

what runs like a string covering actin

A

tropomyosin

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34
Q

what causes troponin to change conformation

A

calcium binding

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35
Q

what happens when troponin binds calcium

A

tropomyosin shifts; exposing actin binding sites for myosin

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36
Q

structure of troponin

A

trimer

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37
Q

normally, intracellular calcium is kept ___

A

low

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38
Q

2 proteins wound together => myosin

A

myosin tails & myosin heads (cross bridges)

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39
Q

what part of myosin binds actin

A

myosin heads

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40
Q

how many myosins = 1 thick filament

A

~500

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41
Q

which direction do myosin heads face

A

1/2 half one way, 1/2 the other

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42
Q

how many thin filaments surround 1 thick filament

A

6; arranged helically

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43
Q

can thin filaments be shared between thick filaments’ 6?

A

yes; between adjacent thick filaments

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44
Q

delineates sarcomere border

A

z disc

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45
Q

where do thin filaments attach

A

z disc

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46
Q

m line

A

where myosin attaches; m= middle

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47
Q

zone of overlap

A

overlap between thick and thin (only thing that increases with contraction)

48
Q

h zone

A

thick filaments only

49
Q

i zone

A

thin filaments only

50
Q

a band

A

length of myosin

51
Q

__ + ___ = a band

A

H zone + zone of overlap

52
Q

where do neuron and muscle fibre communicate

A

neuromuscular junction

53
Q

3 components of NMJ

A

synaptic terminal
synaptic cleft
motor end plate

54
Q

where are cell bodies of motor neurons

A

spinal cord

55
Q

T or F: axon can contact only 1 muscle fibre

A

F; axon can branch into collaterals and contact multiple skeletal fibres

56
Q

what is in synaptic vesicles at NMJ

A

acetylcholine

57
Q

how and where is ACh released after AP

A

exocytosis; synaptic cleft

58
Q

which receptors on motor end plate

A

Acetylcholine receptors

59
Q

what kind of channel is AChR

A

ligand-gated ion channel; ACh (ligand) binding => open

60
Q

what ion depolarizes fibre once AChR open; which direction

A

Na+; influx

61
Q

similarity between muscle fibres and neurons

A

both excitable

62
Q

what happens to ACh after exocytosis

A

broken down by acetylcholerinesterase (AChE) in synaptic cleft; taken up by synaptic terminal, reused

63
Q

Na moves _____ its concentration gradient

A

down

64
Q

when does ACh release stop

A

when AP ends

65
Q

how do muscle fibres control Ca2+ levels

A

actively; pump into SR (terminal cisterna), ECF

66
Q

how does AP reach SR

A

travels down T tubule (membrane extension); contacts terminal cisterna (SR extension)

67
Q

muscle contraction depends on _____ of intracellular Ca2+ upon AP

A

increase

68
Q

with AP, Ca2+ moves ____ its gradient

A

down; into intracellular (concentrated in SR)

69
Q

T or F: myosin heads attach once per AP

A

F; attach, reattach; as long as CA channels open

70
Q

when do ca2+ channels close

A

when membrane potential difference returns to rest

71
Q

muscle relaxation is _____; 3 reasons

A

passive;
elasticity of tissues
pull of antagonist muscles
gravity

72
Q

how many NMJ does a muscle fibre have

A

one

73
Q

motor unit

A

SINGLE motor neuron (spinal cord) and the muscle fibres it innervates

74
Q

what determines force produced by neural control

A

of motor units recruited

75
Q

T or F: motor units have varying # of innervated muscle fibres

A

T

76
Q

T or F: muscle fibres of motor unit all adjacent

A

F; intermingled; tension distributed throughout tissue

77
Q

if less muscle fibres in motor unit

A

precise control i.e. eye movements

78
Q

example of muscle with many fibres/motor unit

A

anti-gravity muscles in back

79
Q

T or F: sometimes, all muscle fibres relaxed

A

F; active; resting tension, but not enough to contract

80
Q

how do antigravity muscles avoid fatigue

A

rotate motor units active

81
Q

what does aerobic metabolism: require? produce?

A

required: O2, organic molecules, mitochondrial enzymes
produced: ATP, CO2

82
Q

what does anaerobic metabolism: require? produce?

A

required: glycogen, glycolytic enzymes
produced: ATP, lactic acid

83
Q

metabolism of slow twitch

A

aerobic (think: takes time to do things right)

84
Q

metabolism of fast twitch

A

anaerobic

85
Q

colour of slow vs fast twitch

A 
slow = red (myoglobin; needs oxygen)
fast = white
86
Q

which muscle type has larger diameter

A

fast twitch (doesn’t have to worry about oxygen diffusion)

87
Q

which muscle type has higher max tension

A

fast twitch; greater diameter

88
Q

which muscle type is fatigue resistant

A

slow; as long as breathing, oxygen supplies ATP (while fast = limited glycogen, glycolytic enzymes)

89
Q

which muscle type can use more substrates for ATP production

A

slow (carbs, lipids, proteins); fast can only use glycogen

90
Q

example locations of slow twitch

A

fatigue resistant; back, legs (like dark meat on chicken)

91
Q

what is required for muscle hypertrophy

A

repeated stimulation to near maximal tension

92
Q

what 3 results increase ATP generating capacity in muscle hypertrophy

A

more mitochondria
more glycogen reserves
more glycolytic enzymes

93
Q

T or F: number of myofibrils and myofilaments increases with muscle hypertrophy

A

true

94
Q

why do muscles get bigger

A

each fibre gets bigger; not increasing #

95
Q

what happens with muscle atrophy

A

reduced myofibrils, myofilaments

fibres become smaller, weaker

96
Q

how are myofibrils removed in muscle atrophy

A

lysosomal activity

97
Q

T or F: muscle atrophy is permanent

A

F; initially reverisble

98
Q

cardiac muscle: # of nuclei

A

1/cell

99
Q

size of cardiac muscle cells

A

smaller than skeletal

100
Q

junctions between cardiocytes

A

intercalated discs

101
Q

what cells set rate of contraction in cardiac

A

pacemaker cells

102
Q

what modules cardiac cells rate

A

autonomic NS, hormones

103
Q

3 junctions at intercalated discs in cardiocytes

A

gap junctions (communication), fascia adherens (in epithelia, zonula adherens; but here, not belt); desmosomes

104
Q

why do cardiac cells contract autonomously

A

unstable membrane potential

105
Q

T or F: cardiocytes can regenerate

A

F; if damaged (i.e. ischemic attack) replaced by fibrous CT

106
Q

location of nuclei in cardiocyte

A

central

107
Q

metabolism of cardiocytes

A

aerobic

108
Q

energy reserves in cardiac muscle

A

glycogen, lipid droplets

109
Q

why is smooth muscle nonstriated

A

myofilaments : irregular arrangement

110
Q

4 locations of smooth muscle

A

respiratory, digestive, reproductive, circulatory

111
Q

what cells set rate of contraction in smooth muscle

A

pacesetter (unstable membrane potential)

112
Q

regeneration in smooth muscle?

A

yes (i.e. hyperplasia in uterus)

113
Q

what makes smooth muscle contract as whole

A

gap junction

114
Q

where are nuclei in SMC

A

central

115
Q

which muscle type has smallest cells

A

smooth muscle

116
Q

which muscle has more nuclei in cross section: cardiac or smooth?

A

smooth; cells are smaller

ANA300 (9 decks)

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