Muscle tissue Flashcards
1
Q
What is the primary protein in thin myofilaments?
A
Actin
2
Q
What are the two types of myofilaments?
A
Thin and thick filaments
3
Q
The interaction of the thin and thick filaments in muscles does what?
A
Produces movement
4
Q
What is a sarcomere?
A
A contractile unit of striated muscle
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
6
Q
What are the three components of thin myofilaments?
A
Actin
Troponin
Tropomyosin
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
8
Q
What is the structure of tropomyosin?
A
2 polypeptide chains that form an alpha helix
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).
10
Q
What is the combined function of troponin and tropomyosin?
A
To block actin
11
Q
How many actin molecules does tropomyosin rest on? What is it doing there?
A
7–blocks active sites of actin
12
Q
What is the primary protein of a myosin filament?
A
Myosin II
13
Q
What does the myosin molecule consist of?
A
2 heavy chains, and 4 light chains
14
Q
What are the two segments of meromyosin?
A
Heavy and light meromyosin
15
Q
What does the heavy meromyosin consist of?
A
4 light chains
2 globular heads
A short, twisted tail
16
Q
What does the light meromyosin consist of?
A
2 chains wrapped around each other in an alpha helix
17
Q
What is the function of adding trypsin to myosin?
A
breaks down into meromyosin
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
19
Q
What does the S1 moiety of myosin consist of?
A
2 light chains and 1 globular head
20
Q
What does the S2 moiety of myosin consist of?
A
the short, twisted tail
21
Q
What is the contractile unit of a muscle cell?
A
Sacromeres
22
Q
What are the structures that contain multiple sarcomeres and extend the length of the cell?
A
Myofibrils
23
Q
Many myofibrils runing parallel to each other form what structure?
A
a muscle fiber
24
Q
What is the 3D shape of a sarcomere?
A
Cylinder
25
What is the disk that separates each cylindrical unit of a sarcomere? What does this area function as?
Z disk
| Functions as an attachment of thin filaments via alpha actinin
26
What is the function of alpha actinin on the z band?
Anchors thin filaments
27
What is in the H band of a sarcomere?
Only thick filaments
28
What is in the I band of a sarcomere?
Only thin filaments in adjacent sarcomeres
29
True or false: the H band is a subset of the A band
True
30
What is the M line of a sarcomere? What is the major protein here?
Consists of protein structures lying between thick filaments, holding them in register.
Creatine kinase is the major protein here
31
What are the proteins that anchors thin filaments to the Z disk?
Alpha actinin and nebulin (x2)
32
What is the protein that anchors the thick filaments to the Z disk?
4 titin molecules
33
What is nebulin?
Inelastic protein that wraps around thin filaments and anchors it to the Z disk
34
What are the proteins that secures thick filaments in register at the M line?
Myomesin and C protein
35
What is the cytoplasmic protein that binds actin filaments to laminin?
Dystrophin
36
What are the components of muscles cells that are specific to muscles cells?
```
Sarcolemma
Sarcoplasm
Sarcosomes
myofibrils
Sarcoplasmic reticulum
myoglobin
Glycogen
```
37
What is the sarcolemma?
cell membrane + exernal lamina +reticular fibers
38
What is the sarcoplasm
Muscle cell cytoplasm
39
What are sarcosomes?
muscle cell mitochondria
40
What are myofibrils?
long, cylindrical chains of sarcomeres
41
What is the sarcoplasmic reticulum?
sER of muscle cells
42
What is the endomysium?
a layer of reticular fibers that surrounds each muscle cell
43
What is the perimysium?
a thin, collagenous connective tissue, derived from the epimysium, and surrounds fascicles of muscles
44
What is the epimysium?
Dense, irregular collagenous tissue that surrounds bunches of fascicles (deep fascia)
45
Deep fascia in anatomy = what in histology?
Epimysium
46
Nerves and vessels from the epimysium travel through what layer of the muscle to end up n each muscle cell?
The perimysium
47
Where do the nuclei sit in muscle cells? How many are there per muscle cell?
Multiple nuclei per cell, which sit at the sarcolemma (plasma membrane)
48
Are muscle cell nuceli euchromatic or heterochromatic? What shape are they?
Euchromatic
oval shaped
49
What is the ECM that sits just outside the sarcolemme? What type of fibers are in this area?
External lamina filled with reticular fibers
50
Can you see the A or Z band at the LM level?
No
51
What are the transverse tubules? What are their function?
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
Where is the sarcoplasmic reticulum found?
Form a "lacy" sleeve around each myofibril
53
Nerve cell impluses travel through what to reach myofibrils?
The T tubules
54
What are terminal cisternae?
Terminal part of T tubules that end on the sarcoplasmic reticulum, and hold Ca
55
What is a triad (in terms of muscle cells)? Where are these found?
1 T tubule + 2 terminal cisternae. Found at the A-I junction of a sarcomere
56
What are the regenerative cells that lie between the skeletal muscle cell and its external lamina? What are their function?
Satellite cells
| They proliferate when the tissue is injured to form new myoblasts
57
What must be present in order for new myotubes to form from satellite cells? What happens if this is not present?
The external lamina
If this is not present, scar tissue forms from fibroblasts instead
58
What is a motor unit?
A lower motor neuron and all of the muscle fibers it innervates
59
What is the neuromuscluar junction?
The synapse of the motor neuron and its muscle
60
What is the neurotransmitter that the axon terminals contain?
Acetylcholine
61
What does a motor end plate consist of?
Axon terminal, synaptic cleft and the muscle cell sarcolemma
62
What is myasthenia gravis?
Autoimmune disease where acetylcholine receptors are attacked by antibodies. Causes progressive weakness d/t receptor destruction.
63
What is Duchenne muscular dystrophy (DMD)?
X-linked recessive disease that has a mutation of dystrophin
64
What is the function of dystrophin
Protein that connects actin filament near the Z discs to the laminin in the ECM
65
Histologically, what are the differences between cardiac and skeletal muscles?
Cardiac muscles are shorter than skeletal muscles, are branched, and contain many more capillaries in the surrounding spaces
66
True or false: cardiac muscles contain glycogen and lipid droplets
True
67
Do cardiac muscles have stronger or weaker striations than skeletal muscles?
Weaker
68
How many nuclei do cardiac muscles have? Where are they located within the cell?
1-2, centrally located
69
What are atrial granules? Where are they found
Granules that contain atrial natriuretic factor and BNP (diauretics), usually found in the right atrium
70
What are intercalated discs? What type of muscles are these specific to?
Specialized intercellular junctions between cardiac muscles
71
What does the transverse portion of the intercalated disc do (3)?
1. Anchors actin filaments of terminal sarcomere to plasma membrane
2. transmits contractile forces from cell-cell
3. binds cells together via desmosomes
72
What does the lateral portion of the intercalated discs do?
Has gap junctions that permit the flow of ions from cell to cell so cardiac muscles contract together
73
Do purkinje fibers tend to stain darker or paler than other muscle cells? What do they contain?
Paler
Glycogen and few myofilaments
74
What is the function of the Purkinje fibers?
To relay electrical impulses to cardiac muscle fibers
75
What are the three structures that form the heart's intrinsic conducting system?
AV node
SA node
Purkinje fibers
76
What percent of cardiac muscles cells volume is occupied by mitochondria?
50%
77
What is abundant in cardiac muscle cells?
Myoglobin
78
Injury to the heart muscle is repaired with what type of tissue?
Fibrous connective tissue
79
What are the three layers of the heart?
Endocardium
Myocardium
Epicardium
80
What layer of the heart are Perkinje fibers located in?
Endocardium
81
What type of structure do smooth muscle cells form?
Sheets
82
Where is smooth muscle found?
Pharynx, esophagus, stomach, small intestine, large intestine, vessel walls, jrespiratory tract
83
What do smooth muscle cells lack that are skeletal muscle cells have?
Striations
84
What proteins do smooth muscle cells have?
Myosin and actin, but NO troponin
85
How many nuclei are in smooth muscle cells?
Only one (mononuclear)
86
What is the shape of smooth muscle cells?
Fusiform
87
Are the nuclei of smooth muscle cells euchromatic or heterochromatic?
Euchromatic
88
Where are the nuclei of smooth muscle cells?
Center of the cell
89
How much space is between smooth muscle cells? Skeletal? Cardiac?
None in smooth
Present in cardiac and skeletal
90
Looking at a EM slide of smooth muscle cells, you see small bubbles near the border of the cell. What are these?
Caveolae -coated vesicles containing Ca
91
What are caveolae?
Pinocytotic vesciles in smooth muscles that release Ca into the cell for contraction
92
What criss-crosses the smooth muscle cells?
Myofilaments
93
What are dense bodies?
Connections of myofilaments either:
1. on the cell membrane
2. Cytoplasmic at myofilament bundles located in the cytoplasm
94
What is the function of dense bodies on the cell membrane of smooth muscle cells?
Contract the cell and cause a puckering
95
Ca released from the sarcoplasmic reticulum of muscle cells binds where?
To the Troponin I complex
96
What happens to the confomation of the actin filament when Ca binds?
Changes conformation, and exposes myosin binding site on actin
97
What happens to the distance between Z disks during contraction?
Get closer
98
What happens to the free end of the actin molecule in contraction?
Get closer to the A band
99
What happens to the length of the thin filaments during contraction? Thick?
They both remain the same
100
What happens to the width of the A band during contraction?
Stays the same
101
What happens to the width of the I band during contraction?
Gets narrow
102
What happens to the width of the H band during contraction?
Disappears
