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Histology > Muscle Tissue Part 1 > Flashcards

Muscle Tissue Part 1 Flashcards

1
Q

Most important characteristics of muscles tissue

A

Contractility and Conductivity

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2
Q

What gives muscle tissue it’s ability to contract?

A

Actin, myosin, ATP

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3
Q

3 major types of muscle cells

A

Skeletal, smooth, cardiac

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4
Q

Characteristics of skeletal muscle

A

Attached to the skeleton, voluntary, cross-striations, used for locomotion/respirations. Quick acting but tire fast. Multi-nucleated.

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5
Q

Characteristics of Smooth muscle

A

Primarily in walls of internal organs. No striations. Involuntary

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6
Q

Characteristics of Cardiac muscle

A

Branching striated tissue. Found only in the heart. Involuntary.

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7
Q

Sarcolemma

A

Specialized plasma membranes of muscle tissue

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8
Q

Sarcoplasm

A

Cytoplasm of the muscle cell

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9
Q

Sarcoplasmic Reticulum

A

Specialized endoplasmic reticulum of muscle cells

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10
Q

Origin of skeletal muscles

A

Myoblasts of the embryonic mesenchymal cells

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11
Q

Skeletal muscle fiber

A

Each fiber is a cell. Multinucleated syncytium

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12
Q

T-tubules

A

Long processes formed by the sarcolemma that carry the action potential deep into the sarcoplasm

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13
Q

Where are the nuclei of skeletal muscles found?

A

Peripheral and immediately deep to the sarcolemma

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14
Q

What does the sarcoplasm of skeletal muscle contain?

A

Myofibrils, filamentous mitochondria, myoglobin, sarcoplasmic reticulum

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15
Q

Myofibrils

A

Contractile filaments are in the myofibrils that gives the striated appearance

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16
Q

Filamentous mitochondria

A

Lie between the myofibrils and close to the sarcolemma. Are the the source of ATP for myofibrils

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17
Q

Myoglobin

A

Oxygen-binding protein in skeletal muscle cells

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18
Q

Sarcoplasmic reticulum

A

Specialized form of SER. Used for deposit of Ca. Releases Ca into the cytoplasm initiating muscle contraction

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19
Q

Thin filaments of muscle fiber

A

F-Actin, Tropomyosin, Troponin Complex

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20
Q

How are muscle fibers arranged?

A

Hexagonal array

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21
Q

F-Actin

A

Forms the double-stranded helical filament (is the polymerization of G-actin)

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22
Q

Tropomyosin

A

Forms filaments that lie in the groove between 2 actin monomers. Masks the myosin-binding sites on actin filament.

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23
Q

Troponin Complex

A

Attached to tropomyosin. Has Troponin T, I, C subunits

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24
Q

Troponin T

A

Binds to tropomyosin, anchoring the complex

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25
Q

Troponin I

A

Binds to actin

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26
Q

Troponin C

A

Binds to Ca (essential part of muscle contraction). Smallest subunit.

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27
Q

Thick filaments of muscle fiber

A

Myosin II

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28
Q

What does Myosin II consist of?

A

2 heavy chains: α-helices
2 globular heads: ATPase and motor activity
2 light chains: attach to heads

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29
Q

Where are the binding sites for ATP and actin?

A

Thick filament myosin II globular heads

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30
Q

What are the dark bands of myofibril made of ?

A

A-bands

31
Q

What are the light bands of myofibril made of?

A

I-bands

32
Q

What are the areas of A-bands?

A

H-zone and M-line

33
Q

H-zone

A

Part of A-bands that contains ONLY thick filaments

34
Q

M-line

A

Dense line that bisects the H-zone. Formed by accessory protein (myomesin). Holds thick filaments in register

35
Q

I-band

A

Pale area formed primarily by thin filaments. Is bisected by Z-disk

36
Q

Z-disk

A

Composed of accessory proteins (α-actinin). Provides anchoring points for thin filaments. Supports architecture of myofibrils

37
Q

Sarcomere

A

Portion of the myofibril between 2 adjacent Z-disks. Basic contractile unit of skeletal muscle.

38
Q

In what muscle fiber unit does muscle contraction take place?

A

Sarcomere (shortens)

39
Q

What bands change during muscle contraction?

A

I-band, H-zone shrink

40
Q

What band(s) do NOT change during muscle contraction?

A

A-band

41
Q

What maintains precise alignment of thick and thin filaments of muscle fibers?

A

Accessory proteins, make up less than 25% of total muscle fiber protein

42
Q

8 types of accessory proteins

A

α-actinin. Nebula. Tropomodulin. Titin. Myomesin. C-protein. Desmin. Dystrophin.

43
Q

α-Actinin

A

Short, bipolar, rod-shaped protein. Actin-binding. bundles thin filaments into parallel arrays and anchors them at the Z-line

44
Q

Nebulin

A

Elongated, inelastic proteins. Attached to Z-lines and runs parallel to thin filaments. Helps α-actinin anchor thin filaments. Regulates length of thin filaments during muscle development

45
Q

Tropomodulin

A

Small, actin-binding protein (actin-capping). Attached to the free portion of the thin filament. Maintains/regulates length of sarcomeric actin filament.

46
Q

Titin

A

Large protein. Forms elastic lattice that anchors filaments in the Z-line. 2 “springs” off of the protein help stabilize the centering of the myosin-containing thick filament. Prevents excessive stretching of the sarcomere.

47
Q

Myomesin

A

Myosin-binding protein. Holds thick filaments in line at the M-line

48
Q

C protein

A

Myosin-binding protein. Holds thick filaments in line at the M-line. Forms several distinct transverse stripes on either side of the M-line.

49
Q

Desmin

A

Type of intermediate filament. Forms lattice that surrounds the sarcomere at the level of the Z-lines, attaching them to one another/plasma membrane. Forms stabilizing cross-links between neighboring myofibrils

50
Q

Dystrophin

A

Large protein. Links laminin in external lamina of the muscle cell to the actin filaments

51
Q

Muscular dystrophy

A

Mutations in the structural proteins of skeletal muscle. Results in severe muscle weakness, muscle atrophy, and destruction of muscle fibers.

52
Q

Duchenne’s muscular dystrophy

A

Absence of dystrophin protein

53
Q

Membrane Triad components

A

Formed by scarcoplasmic reticulum. One T-tubule and 2 cisternae

54
Q

T-tubular system

A

Formed by deep invaginations of the sarcolemma. Allows impulse to travel down the cell and excite terminal cisternae. Run at junction of A and I bands

55
Q

Terminal Cisternae

A

Formed by the sarcoplasmic reticulum. Run parallel to T-tubules on both sides (triad formed). Contain high [Ca++]. Run near the boundary of A and I bands.

56
Q

What does an action potential cause in the sarcolemma/sarcoplasmic reticulum?

A

Descends down along the T-tubules, causing the release of Ca++ into the sarcoplasm.

57
Q

What ion’s influx causes muscle contraction?

A

Ca++

58
Q

What does Ca++ bind to in the sarcoplasm and what does it do?

A

Troponin C, causing the spatial configuration of troponin to change, moving it away from the myosin-binding sites on the actin

59
Q

What does myosin use to move along the actin filament?

A

ATP

60
Q

Stage 1 of contraction cycle

A

Attachment: rigor configuration

61
Q

Rigor configuration

A

Myosin head is tightly bound to the actin molecule of the thin filament (ATP is absent)

62
Q

Rigor Mortis

A

Lack of ATP causes myosin to remain bound to actin

63
Q

Stage 2 of contraction cycle

A

Release: ATP induces conformational changes to the myosin head, so myosin is released from actin

64
Q

Stage 3 of contraction cycle

A

Bending: ATP is broken into ADP and Pi (inorganic phosphate). Myosin head bends

65
Q

Stage 4 of contraction cycle

A

Force generation: Myosin head binds to actin again. Power stroke happens. Forces actin filament along the thick filament

66
Q

Power stroke

A

Release of Pi from myosin head causes head to generate a force and returns to its initial position

67
Q

Stage 5 of contraction cycle

A

Reattachment: myosin head is attached to new actin and is ready for a new cycle

68
Q

Relaxation of skeletal muscle

A

Ca++ activated ATPase pumps transport Ca to the sarcoplasmic reticulum. Ca disassociates from troponin C. Troponin returns to initial configuration blocking the actin/myosin interaction.

69
Q

Which cells cause regeneration of skeletal muscle?

A

Satellite cells

70
Q

What are the actions of satellite cells?

A

Activated after injury, proliferate, give rise to mew myoblasts. Myoblasts fuse to form new fiber

71
Q

How do muscles respond to aging?

A

Increase in diameter

72
Q

How do muscles respond to exercising?

A

hypertrophy

73
Q

How do muscles respond to disuse?

A

Atrophy

74
Q

Layers of connective tissue sheaths?

A

Endomysium: most internal layer, around each muscle fiber
Perimysium: Thicker layer, surrounds groups of muscle fibers
Epimysium: most external layer, surrounds groups of fascicles (makes the muscle)

Histology (8 decks)

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