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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
triad in skeletal muscle
t tubule with adjacent terminal cisterna
26
bundles of myofilaments
myofibrils
27
2 types of myofilaments
actin (thin), myosin (thick)
28
what feature => striations
sarcomeres
29
how long are myofibrils relative to cell
length of whole cell
30
2 types of actin
``` G actin (globular subunit) F actin (filamentous; 300-400 G actin) ```
31
what covers actin binding sites
tropomyosin
32
what holds tropomyosin in place
troponin
33
what runs like a string covering actin
tropomyosin
34
what causes troponin to change conformation
calcium binding
35
what happens when troponin binds calcium
tropomyosin shifts; exposing actin binding sites for myosin
36
structure of troponin
trimer
37
normally, intracellular calcium is kept ___
low
38
2 proteins wound together => myosin
myosin tails & myosin heads (cross bridges)
39
what part of myosin binds actin
myosin heads
40
how many myosins = 1 thick filament
~500
41
which direction do myosin heads face
1/2 half one way, 1/2 the other
42
how many thin filaments surround 1 thick filament
6; arranged helically
43
can thin filaments be shared between thick filaments' 6?
yes; between adjacent thick filaments
44
delineates sarcomere border
z disc
45
where do thin filaments attach
z disc
46
m line
where myosin attaches; m= middle
47
zone of overlap
overlap between thick and thin (only thing that increases with contraction)
48
h zone
thick filaments only
49
i zone
thin filaments only
50
a band
length of myosin
51
__ + ___ = a band
H zone + zone of overlap
52
where do neuron and muscle fibre communicate
neuromuscular junction
53
3 components of NMJ
synaptic terminal synaptic cleft motor end plate
54
where are cell bodies of motor neurons
spinal cord
55
T or F: axon can contact only 1 muscle fibre
F; axon can branch into collaterals and contact multiple skeletal fibres
56
what is in synaptic vesicles at NMJ
acetylcholine
57
how and where is ACh released after AP
exocytosis; synaptic cleft
58
which receptors on motor end plate
Acetylcholine receptors
59
what kind of channel is AChR
ligand-gated ion channel; ACh (ligand) binding => open
60
what ion depolarizes fibre once AChR open; which direction
Na+; influx
61
similarity between muscle fibres and neurons
both excitable
62
what happens to ACh after exocytosis
broken down by acetylcholerinesterase (AChE) in synaptic cleft; taken up by synaptic terminal, reused
63
Na moves _____ its concentration gradient
down
64
when does ACh release stop
when AP ends
65
how do muscle fibres control Ca2+ levels
actively; pump into SR (terminal cisterna), ECF
66
how does AP reach SR
travels down T tubule (membrane extension); contacts terminal cisterna (SR extension)
67
muscle contraction depends on _____ of intracellular Ca2+ upon AP
increase
68
with AP, Ca2+ moves ____ its gradient
down; into intracellular (concentrated in SR)
69
T or F: myosin heads attach once per AP
F; attach, reattach; as long as CA channels open
70
when do ca2+ channels close
when membrane potential difference returns to rest
71
muscle relaxation is _____; 3 reasons
passive; elasticity of tissues pull of antagonist muscles gravity
72
how many NMJ does a muscle fibre have
one
73
motor unit
SINGLE motor neuron (spinal cord) and the muscle fibres it innervates
74
what determines force produced by neural control
of motor units recruited
75
T or F: motor units have varying # of innervated muscle fibres
T
76
T or F: muscle fibres of motor unit all adjacent
F; intermingled; tension distributed throughout tissue
77
if less muscle fibres in motor unit
precise control i.e. eye movements
78
example of muscle with many fibres/motor unit
anti-gravity muscles in back
79
T or F: sometimes, all muscle fibres relaxed
F; active; resting tension, but not enough to contract
80
how do antigravity muscles avoid fatigue
rotate motor units active
81
what does aerobic metabolism: require? produce?
required: O2, organic molecules, mitochondrial enzymes produced: ATP, CO2
82
what does anaerobic metabolism: require? produce?
required: glycogen, glycolytic enzymes produced: ATP, lactic acid
83
metabolism of slow twitch
aerobic (think: takes time to do things right)
84
metabolism of fast twitch
anaerobic
85
colour of slow vs fast twitch
``` slow = red (myoglobin; needs oxygen) fast = white ```
86
which muscle type has larger diameter
fast twitch (doesn't have to worry about oxygen diffusion)
87
which muscle type has higher max tension
fast twitch; greater diameter
88
which muscle type is fatigue resistant
slow; as long as breathing, oxygen supplies ATP (while fast = limited glycogen, glycolytic enzymes)
89
which muscle type can use more substrates for ATP production
slow (carbs, lipids, proteins); fast can only use glycogen
90
example locations of slow twitch
fatigue resistant; back, legs (like dark meat on chicken)
91
what is required for muscle hypertrophy
repeated stimulation to near maximal tension
92
what 3 results increase ATP generating capacity in muscle hypertrophy
more mitochondria more glycogen reserves more glycolytic enzymes
93
T or F: number of myofibrils and myofilaments increases with muscle hypertrophy
true
94
why do muscles get bigger
each fibre gets bigger; not increasing #
95
what happens with muscle atrophy
reduced myofibrils, myofilaments | fibres become smaller, weaker
96
how are myofibrils removed in muscle atrophy
lysosomal activity
97
T or F: muscle atrophy is permanent
F; initially reverisble
98
cardiac muscle: # of nuclei
1/cell
99
size of cardiac muscle cells
smaller than skeletal
100
junctions between cardiocytes
intercalated discs
101
what cells set rate of contraction in cardiac
pacemaker cells
102
what modules cardiac cells rate
autonomic NS, hormones
103
3 junctions at intercalated discs in cardiocytes
gap junctions (communication), fascia adherens (in epithelia, zonula adherens; but here, not belt); desmosomes
104
why do cardiac cells contract autonomously
unstable membrane potential
105
T or F: cardiocytes can regenerate
F; if damaged (i.e. ischemic attack) replaced by fibrous CT
106
location of nuclei in cardiocyte
central
107
metabolism of cardiocytes
aerobic
108
energy reserves in cardiac muscle
glycogen, lipid droplets
109
why is smooth muscle nonstriated
myofilaments : irregular arrangement
110
4 locations of smooth muscle
respiratory, digestive, reproductive, circulatory
111
what cells set rate of contraction in smooth muscle
pacesetter (unstable membrane potential)
112
regeneration in smooth muscle?
yes (i.e. hyperplasia in uterus)
113
what makes smooth muscle contract as whole
gap junction
114
where are nuclei in SMC
central
115
which muscle type has smallest cells
smooth muscle
116
which muscle has more nuclei in cross section: cardiac or smooth?
smooth; cells are smaller

ANA300 (9 decks)

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