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Cell Biology > Exam 2: Muscles > Flashcards

Exam 2: Muscles Flashcards

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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
Q

alpha-actinin

A

component of Z-disk

anchors thin filament to Z-disk

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26
Q

nebulin

A

nonelastic protein, wrapped around each thin filament

anchors thin filament to Z-disk

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27
Q

Myomesin

A

secures thick filament at M-line

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28
Q

C protein

A

secures thick filament at M-line

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29
Q

Dystrophin

A

cytoplasmic protein that binds actin to laminin of external lamina surrounding muscle fiber

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30
Q

Sarcolemma

A

cell membrane, external lamina, and reticular lamina

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31
Q

Sarcoplasmic reticulum

A

muscle cell smooth endoplasmic reticulum

32
Q

Endomysium

A

surrounds each muscle fiber (cell)

delicate layer of reticular fibers

33
Q

perimysium

A

surround many fibers as a group to form a fascicle (bundle)

thin, collagenous connective tissue

34
Q

epimysium

A

dense, irregular collagenous connective tissue that encloses fascicles to form gross muscle

35
Q

Skeletal muscle

A

striated muscle
voluntary movement
quick and forceful contractions

36
Q

Cardiac muscle

A

heart, striated, involuntary

contraction is rigorous and rhythmic

37
Q

Smooth muscle

A

non-striated, involuntary

slow contraction

38
Q

Muscle cell nuclei are

A

oval-fusiform shape and euchromatic

39
Q

Skeletal muscle nuclei are located

A

on cell periphery

40
Q

Transverse tubules (T-tubules)

A

invaginations of cell membrane (sarcolemma)
Lumen continuous with extracellular space and contain extracellular fluid
Carries nerve impulses deep into cell

41
Q

Terminal cisternae

A

store calcium in lumen

form triad at A-I junction of sarcomere

42
Q

Satellite cells

A

regenerative cells that lie between skeletal muscle and its external lamina
Proliferate after injury and form new myoblasts

43
Q

Myasthenia Graves

A

autoimmune disease causing muscle weakness

Antibodies bind to acetylcholine receptors, preventing muscle contraction

44
Q

Muscular Dystrophy

A

genetic, degenerative disease affecting striated muscles

45
Q

Duchenne muscular dystrophy (DMD)

A

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
Q

Cardiac muscle

A 
weakly striated (sarcomeres and myofibrils present)
Cells short and branched
Contain glycogen deposits
47
Q

Lipofuscin

A

aging pigment, present in cardiac muscle cells of older people

48
Q

Cardiac muscle nuclei

A

are located in center of cell

49
Q

Atrial granules (membrane bound granules)

A

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
Q

Cardiac muscle cells are covered in

A

endomysium - contain many capillaries

51
Q

Intercalated discs

A

specialized intercellular junctions of myocardium

52
Q

Transverse portion of intercalated disc

A

perpendicular to long axis of muscle fiber

Contains Fascia adherens - anchor actin filaments & Maculae adherents (desmosomes) - bind cells together

53
Q

Lateral portion of myocardial intercalated discs

A

parallel to cells fibers

Contain gap junctions - permit flow of ions from cell to cell

54
Q

Purkinje fibers

A

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
Q

Heart muscle damage can be detected by

A

high troponin blood levels

56
Q

Smooth muscle

A

forms sheets, no striations

Nucleus in center of cell - largest width

57
Q

Dense bodies

A

myofilament bundles attach on internal surface of smooth muscle cell membrane

58
Q

Caleolae

A

bubble-like structures on inner surface of cell membrane in smooth muscle cells - release Ca into cell for contraction

59
Q

A nerve impulse is transmitted

A

down the nerve cell axon until it reaches the pre-synaptic membrane

60
Q

What ions enter the pre-synaptic terminal following a nerve impulse?

A

Calcium ions

61
Q

Ca ions trigger

A

synaptic vesicle to release their neurotransmitters into the synaptic cleft

62
Q

What neurotransmitter triggers muscle contraction

A

Achetocholine

63
Q

Following Ach receptor binding, what is the ion exchange in the skeletal muscle cell?

A

Na ions enter the cell, K ions leave the cell - sarcolemma is depolarized

64
Q

Nerve impulse is carried deep into the muscle cell by

A

T-tubules

65
Q

Sarcoplasmic reticulum contains what protein?

A

calsequestrin, which stores Ca ions

66
Q

After the sarcoplasmic reticulum is depolarized, what ion is released?

A

Calcium ions, which bind to the TnC subunit of troponin complex

67
Q

Binding of Ca ions to troponin causes

A

a conformation change, causing TnT subunit to push tropomyosin deeper into the actin groove uncovering actin active sites

68
Q

Uncovering the actin active sites allows

A

myosin head to bind to the actin monomor, pulling the actin filament over the myosin filament

69
Q

What is needed for myosin to move the actin filament?

A

ATP energy

70
Q

Myosin slides the actin filament in which direction during contraction

A

closer to the midline of the sarcomere (M-band), shortening the sarcomere

71
Q

During contraction the length of the thin and thick filaments

A

remains the same, their relative position is what changes

72
Q

During contraction the A-band

A

remains the same size

73
Q

During contraction the H-band and I-band

A

become smaller

74
Q

During contraction the Z-discs

A

come closer toward the midline

75
Q

Rigor mortis

A

at death, the actin-myosin complexes can’t dissociate since ATP is not available, so muscles stiffen

Cell Biology (20 decks)

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