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unit 4 Flashcards

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1
Q

what are the four properties of muscle?

A

excitability, contractility, extensibility, elasticity

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2
Q

what does a skeletal muscle consist of?

A

contractile tissue composed of muscle cells
a series of collagen-based connective tissue coverigs

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3
Q

what do the connective tissue coverings do?

A

bind muscle fibers, link skeletal muscle to bone, transduce force to attached structures, convey neurovasculature

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4
Q

how are skeletal muscle cells developed?

A

myoblasts fuse to form a single skeletal muscle cell
once fusion occurs, muscle fibers cannot divide

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5
Q

how do muscles enlarge?

A

by hypertrophy

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6
Q

what are satellite cells?

A

myoblasts that remain in muscle
stem cell like cells

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7
Q

how does muscle fiber regeneration occur?

A

satellite cells divide and fuse to form new muscle fibers
they are activated when needed for healing

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8
Q

features of skeletal muscle

A

long cylindrical cells, multinucleate, appears striated due to overlapping thick and thin filaments

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9
Q
A

longitudinal skeletal muscle

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10
Q
A

cross section skeletal muscle

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11
Q

endomysium

A

layer of reticular fibers that surrounds individual muscle fibers

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12
Q

perimysium

A

CT layer that surrounds a group of fibers to form a fascicle

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13
Q

epimysium

A

dense CT that surrounds a collection of fascicles
deep fascia that surrounds muscle

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14
Q

what is a fascicle

A

multiple muscle fibers grouped
functional unit of muscle

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15
Q
A

denervation atrophy of skeletal muscle due to motor neuron damage

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16
Q

what is the myotendinous junction?

A

site of attachment of a muscle fiber and the contiguous CT of the tendon

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17
Q

what is the purpose of a myotendinous junction?

A

increase SA of contact and enhance adhesion

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18
Q

what surrounds each muscle fiber?

A

capillary beds

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19
Q

where are the parts of a nerve that go to skeletal muscle?

A

cell body - SC or brain
axon - in neurovascular bundle to muscle

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20
Q

fine movement

A

a few branches innervate a small number of muscle fibers

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21
Q

gross movement

A

many branches innervate thousands of muscle fibers

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22
Q

red fibers

A

type I, slow
slow contraction speed, fatigue resistant

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23
Q

intermediate fibers

A

type IIa, fast oxidative-glycolytic
fast contraction speed, relatively fatigue resistant

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24
Q

white fibers

A

type IIb, fast glycolytic, fast twitch
fastest contraction speed, fatigue quickly

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25
structure of myofibrils
long bundles of myofilaments that extend the entire length of the fiber and occupy most of the sarcoplasm
26
A band
contain thick filaments and overlapping thin filaments
27
I band
remaining thin filament
28
Z line
protein dense regions separating sarcomeres
29
H zone
portion of A band containing only thick filaments and no myosin heads
30
M line
protein dense region in the middle of the H zone
31
32
how are adjacent sarcomeres structured?
they are aligned
33
what is myosin?
a molecular motor protein that is a major component of thick filaments
34
what are myosin composed of?
2 heavy chains and 4 light chains
35
structure of myosin
tails associate in antiparallel fashion with a central bare zone and myosin heads that radiate around ends
36
what does a myosin head contain?
actin binding site and ATP binding site
37
what is actin?
a major component of thin filaments that contains a binding site for myosin head
38
what does tropomyosin do?
covers myosin binding sites on actin
39
what does troponin T, I, and C do?
T - binds to tropomyosin I - binds to actin C - binds to calcium
40
what does the binding of TnC and Ca do?
causes conformational change where tropomysoin moves to make the binding site on actin accessible
41
which filament slides during muscle contraction?
thin filaments slide over thick filaments toward M line
42
what zones/bands change during muscle contraction?
Z discs, I bands, H zone
43
what is the sarcoplasmic reticulum?
a special type of sER that is composed of membranous sacs and anastomosing channels encircling each myofibril
44
terminal cisternae
dilated sacs at ends of each sarcoplasmic reticulum networks
45
what is the function of the sarcoplasmic reticulum?
stores high concentrations of stored Ca2+ in terminal cisternae
46
where are mitochondria and glycogen deposits located?
adjacent to sarcoplasmic reticulum
47
what are transverse tubules (T-tubules)
invaginations of sarcolemma into the cell
48
what do T-tubules form?
a network of channels lined by specialized plasma membrane that wrap around each myofibril
49
triad
t-tubules associate with terminal cisternae of two sarcomeres
50
neuromuscular junction structure
axon forms a dilation called axon terminus that houses synaptic vesicles axon termini lie in a depression of the sarcolemma
51
function of neuromuscular junction
initiate events that lead to skeletal muscle contraction: Ach released and binds to AchR on sarcolemma, leads to influx of Na+, depolarizes membrane, action potential is reached
52
once an action potential is reached at the NMJ, what happens?
Ca2+ released from SR into sarcoplasm cause troponin to move tropomyosin, the contraction cycle begins
53
contraction cycle
54
longitudinal cardiac muscle
55
cross section cardiac muscle
56
three types of cell junctions in intercalated discs
fascia adherens, desmosomes, gap junctions
57
fascia adherens
hold cells together, link to actin in nearest sarcomere similar to adherens junctions
58
desmosomes
hold cells together, link to IF network similar to maculae adherens
59
gap junctions
spread action potential , allow for coordinated contraction
60
how is contraction of cardiac muscle initiated?
by cardiac conducting cells (modified cardiomyocytes)
61
cardiac muscle contraction
membrane is depolarized which extends to T-tubules signals SR, releases Ca2+ Ca2+ binds to TnC...
62
how does the depolarization signal travel in cardiac cells?
from one cell to the next via gap junctions, slower than skeletal muscle
63
cross section smooth muscle
64
longitudinal smooth muscle
65
unique features of smooth muscle
no T-tubules non-striated stretchier and greater contractile time can contract in wave pattern or along the entire length robust cell proliferation
66
visceral smooth muscle
in walls of vasculature and hollow organs connected via gap junctions for rapid spread of action potential
67
multiunit smooth muscle
few gap junctions, each cell acts independently
68
myofilaments in smooth muscle
organized into bundles that are oriented in all directions
69
initiation of smooth muscle contraction
electrical, mechanical, chemical
70
smooth muscle contraction
thin filaments slide past thick which generates tension transmitted to IFs, IFs pull on sarcolemma shortening occurs in all directions

histology (15 decks)

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