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Cell Biology > Exam 2: Muscles > Flashcards

Exam 2: Muscles Flashcards

(75 cards)

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1
Q

Thin filaments consist primarily of protein

A

actin

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2
Q

thin filaments are made of

A

F-actin, Troponin complex, Tropomyosin

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3
Q

G-actin monomers assemble to form

A

a polymer - 2 polymers become twisted to form a double-stranded helix (filamentous actin)

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4
Q

Troponin complex is made of

A

3 subunits (TnT, TnC, TnI)

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5
Q

TnT

A

attaches to Tropomyosin

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6
Q

TnC

A

binds Ca ions

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7
Q

TnI

A

binds troponin complex to actin

Inhibits actin-myosin interaction

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8
Q

Tropomyosin molecule consists of

A

2 polypeptide chains which form an alpha helix

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9
Q

Each tropomyosin molecule rests on

A

7 G-actin molecules and covers their active sites for myosin

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10
Q

Thick filaments consist of protein

A

myosin II

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11
Q

Myosin consists of

A

2 heavy chains (golf club heads) and 4 light chains

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12
Q

Heavy meromyosin

A

4 light chains + 2 globular heads (2 S1 moieties), and a short twisted tail (S2 segment)

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13
Q

Light meromyosin

A

long twisted tail - 2 chains wrapped around each other in an alpha-helix

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14
Q

sarcomere

A

overlapping actin (thin) and myosin (thick) myofilaments

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15
Q

myofibrils

A

long cylindrical series of end-to-end sarcomeres

Extend length of muscle cell

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16
Q

Muscle Fiber (cell)

A

many parallel myofibrils

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17
Q

Contractile unit of skeletal muscle is

A

a sarcomere

Z-line to Z-line

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18
Q

A-band

A

Dark band
thick and thin filaments
widest band

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19
Q

H-band

A

Thick filament only

bisects A-band

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20
Q

I-band

A

light band, thin filament only

Made of portions of adjacent sarcomeres

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21
Q

Z-line (disk)

A

attachment for thin filaments
Contains alpha-actinin, which anchors actin filaments to Z-disk
bisects I-band

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22
Q

M-line

A

consists of protein structures lying between thick filaments, holding them
Bisects H-band

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23
Q

Major protein in M-line

A

creatine kinase

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24
Q

Titin molecules

A

elastic protein

4 molecules anchor thick filament to Z-discs

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25
alpha-actinin
component of Z-disk | anchors thin filament to Z-disk
26
nebulin
nonelastic protein, wrapped around each thin filament | anchors thin filament to Z-disk
27
Myomesin
secures thick filament at M-line
28
C protein
secures thick filament at M-line
29
Dystrophin
cytoplasmic protein that binds actin to laminin of external lamina surrounding muscle fiber
30
Sarcolemma
cell membrane, external lamina, and reticular lamina
31
Sarcoplasmic reticulum
muscle cell smooth endoplasmic reticulum
32
Endomysium
surrounds each muscle fiber (cell) | delicate layer of reticular fibers
33
perimysium
surround many fibers as a group to form a fascicle (bundle) | thin, collagenous connective tissue
34
epimysium
dense, irregular collagenous connective tissue that encloses fascicles to form gross muscle
35
Skeletal muscle
striated muscle voluntary movement quick and forceful contractions
36
Cardiac muscle
heart, striated, involuntary | contraction is rigorous and rhythmic
37
Smooth muscle
non-striated, involuntary | slow contraction
38
Muscle cell nuclei are
oval-fusiform shape and euchromatic
39
Skeletal muscle nuclei are located
on cell periphery
40
Transverse tubules (T-tubules)
invaginations of cell membrane (sarcolemma) Lumen continuous with extracellular space and contain extracellular fluid Carries nerve impulses deep into cell
41
Terminal cisternae
store calcium in lumen | form triad at A-I junction of sarcomere
42
Satellite cells
regenerative cells that lie between skeletal muscle and its external lamina Proliferate after injury and form new myoblasts
43
Myasthenia Graves
autoimmune disease causing muscle weakness | Antibodies bind to acetylcholine receptors, preventing muscle contraction
44
Muscular Dystrophy
genetic, degenerative disease affecting striated muscles
45
Duchenne muscular dystrophy (DMD)
most common and severe form Protein dystrophin is absent causes muscle weakness and atrophy of shoulder, hip, pelvic, and thigh muscles As disease progresses affects heart and breathing muscles, leading to death
46
Cardiac muscle
``` weakly striated (sarcomeres and myofibrils present) Cells short and branched Contain glycogen deposits ```
47
Lipofuscin
aging pigment, present in cardiac muscle cells of older people
48
Cardiac muscle nuclei
are located in center of cell
49
Atrial granules (membrane bound granules)
Contain atrial natriuretic factor and brain natriuretic factor Most numerous in muscle fibers of right atrium Diuretic hormones, act on kidneys to lower blood pressure
50
Cardiac muscle cells are covered in
endomysium - contain many capillaries
51
Intercalated discs
specialized intercellular junctions of myocardium
52
Transverse portion of intercalated disc
perpendicular to long axis of muscle fiber | Contains Fascia adherens - anchor actin filaments & Maculae adherents (desmosomes) - bind cells together
53
Lateral portion of myocardial intercalated discs
parallel to cells fibers | Contain gap junctions - permit flow of ions from cell to cell
54
Purkinje fibers
specialized cardiac muscle cells located in endocardium Large, pale staining, contain glycogen deposits Form impulse-conducting system of heart - relay electrical impulses to myocardial fibers
55
Heart muscle damage can be detected by
high troponin blood levels
56
Smooth muscle
forms sheets, no striations | Nucleus in center of cell - largest width
57
Dense bodies
myofilament bundles attach on internal surface of smooth muscle cell membrane
58
Caleolae
bubble-like structures on inner surface of cell membrane in smooth muscle cells - release Ca into cell for contraction
59
A nerve impulse is transmitted
down the nerve cell axon until it reaches the pre-synaptic membrane
60
What ions enter the pre-synaptic terminal following a nerve impulse?
Calcium ions
61
Ca ions trigger
synaptic vesicle to release their neurotransmitters into the synaptic cleft
62
What neurotransmitter triggers muscle contraction
Achetocholine
63
Following Ach receptor binding, what is the ion exchange in the skeletal muscle cell?
Na ions enter the cell, K ions leave the cell - sarcolemma is depolarized
64
Nerve impulse is carried deep into the muscle cell by
T-tubules
65
Sarcoplasmic reticulum contains what protein?
calsequestrin, which stores Ca ions
66
After the sarcoplasmic reticulum is depolarized, what ion is released?
Calcium ions, which bind to the TnC subunit of troponin complex
67
Binding of Ca ions to troponin causes
a conformation change, causing TnT subunit to push tropomyosin deeper into the actin groove uncovering actin active sites
68
Uncovering the actin active sites allows
myosin head to bind to the actin monomor, pulling the actin filament over the myosin filament
69
What is needed for myosin to move the actin filament?
ATP energy
70
Myosin slides the actin filament in which direction during contraction
closer to the midline of the sarcomere (M-band), shortening the sarcomere
71
During contraction the length of the thin and thick filaments
remains the same, their relative position is what changes
72
During contraction the A-band
remains the same size
73
During contraction the H-band and I-band
become smaller
74
During contraction the Z-discs
come closer toward the midline
75
Rigor mortis
at death, the actin-myosin complexes can't dissociate since ATP is not available, so muscles stiffen

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