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Physiology > Skeletal muscle > Flashcards

Skeletal muscle Flashcards

1
Q

What is a sarcolemma?

A

Plasmalemma for muscle cells

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2
Q

What is a sarcomere?

A

The functional unit of a muscle cell; from one I band to another

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3
Q

What is the sarcoplasmic reticulum?

A

Where Ca is stored

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4
Q

What is the transverse tubules (T tubules)?

A

The connection between the outside of a muscle fiber to the outside. Allows for the conduction of electrical signals

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5
Q

What is a muscle fiber?

A

Synonymous with muscle cell

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6
Q

What is a myofibril?

A

Cylindrical structure made up of an end-to-end chain of repeating unit, the sarcomeres

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7
Q

What is titin?

A

The protein that hold the thick filaments to the Z disk

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8
Q

What is dystrophin?

A

The protein in myofibrils that attached an actin filament to a transmembrane protein

(This is the causitive agent of Duchanne’s muscluar dystrophy)

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9
Q

What is a ryanodine receptor?

A

The DHP channel located in the Triad

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10
Q

What are DHP receptors?

A

1

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11
Q

Which is the actin filament (thin or thick)?

A

Thin

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12
Q

Which is the thick filament?

A

Myosin

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13
Q

What is the Z-disc made of?

A

1

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14
Q

What are cross-bridges?

A

1

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15
Q

What is the sliding filament theory of muscle contraction?

A

The fact that the thick filaments slide across the thin filaments

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16
Q

What is the role of ATP in muscle contraction?

A

Detaches the myosin from the actin active site

this is the reason for rigormortis

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17
Q

What is the role of Ca in muscle contraction?

A

binds to the TnC, moving the actin complex, and allowing the myosin head to attach to the actin filament

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18
Q

Which type of muscle is striated?

A

skeletal

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19
Q

Which type of muscle have intercalated discs, and many branches?

A

Cardiac

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20
Q

Which type of muscles have a centrally located nucleus?

A

Smooth

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21
Q

What type of connections do intercalated discs have?

A

Electrical and mechanical (d/t pores)

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22
Q

Which type of muscles have multiunit connections to each cell?

A

Smooth

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23
Q

Smooth muscle cells that have a unitary innervation have what connection between cells? Why?

A

Gap junctions for transmission between cells

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24
Q

What is the layer of CT around a bunch of fasiculi?

A

Epimysium

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25
Q

What is the CT layer around a single fasicle?

A

Perimysium

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26
Q

What is the CT layer around an individual muscle fiber?

A

Endomysium

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27
Q

What are the dominant organelle in muscle cells?

A

Mito

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28
Q

What is the sarcoplasma?

A

The cytosol for muscle cells

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29
Q

What is inside T tubules?

A

Extracellular fluid

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30
Q

What are the components of a triad? What is the importance of this?

A

Sarcolemmas x2 + transverse tubule

allows for conduction of signals from ECF to myofibrils

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31
Q

What is the etiology of Duchenne’s muscular dystrophy?

A

An almost total lack of dystrophin

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32
Q

What is the etiology of Becker’s muscular dystrophy?

A

Mutated, but still somewhat functional dystrophin

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33
Q

Which part of the mrosin protein actually attach to the actin?

A

Heads

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34
Q

What is tropomyosin?

A

The protein that covers the active sites on the actin?

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35
Q

What are the proteins that form the troponin complex?

A

Tnt
TnC
TnI

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36
Q

What do the troponins bind?

A

TnT- tropomyosin
TnC- Ca
TnI-actin

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37
Q

What is the chemical changes that allow a detached myosin head to attach to the actin?

A

Loss of phosphate from head (NOT from ATP)

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38
Q

What is the consequence of ADP being released from the myosin head?

A

Nothing much (look at slide)

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39
Q

How far do muscle fibers extend?

A

The length of the muscle

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40
Q

What are the two components to the sarcolemma?

A

Plasma membrane

Transverse tubules

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41
Q

What is the outer coat of a sarcolemma made of?

A

A thin layer of collagen

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42
Q

What is the area that is between two Z discs?

A

sarcomere

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43
Q

What are the two attachments of a titin protein molecule?

A

Z line

Myosin thick filaments

44
Q

What is the sarcotubular system?

A

The system of transverse tubules and sarcoplasmic reticulum

45
Q

What is the function of the sarcoplasmic system?

A

Transmits action potential throughout the cell,

46
Q

What is the function of the sarcoplasmic reticulum?

A

Stores Ca until signalled by a depolarization to release it into the cytosol

47
Q

How does dystrophin add strength to muscles?

A

connecting fibrils to the ECM

48
Q

What are the two types of striated muscle?

A

Skeletal and cardiac

49
Q

What is the only type of muscle that is not striated?

A

Smooth

50
Q

What is the component of the I band? (the light band)

A

Actin

51
Q

What is the component of the H band?

A

Myosin

52
Q

What are the components of the A band?

A

Where myosin and actin overlap + H band

53
Q

Which type of muscles are connected by gap junctions?

A

Cardiac and smooth muscles–in the intercalated discs for cardiac muscles

54
Q

What are the two kinds of smooth muscle?

A

Multiunit and Unitary

55
Q

Where are nuclei found in skeletal muscle cells?

A

At the periphery

56
Q

What is the unit of muscle that contains just thick and thin filaments?

A

Myofibril

57
Q

What are bunches of myofibrils called?

A

Muscle fibers

58
Q

What are bunches of muscle fibers called?

A

Fascicles

59
Q

What is the M line?

A

The central line in the sarcomere

60
Q

What is the cause of familiar dilated cardiomyopathy?

A

Titin mutation

61
Q

What is the cause of hereditary myopathy with early respiratory failure?

A

Titin mutation

62
Q

What is the mode of inheritance for Duchenne’s muscular dystrophy?

A

X-linked recessive

63
Q

What is the cause of the limb-girdle dystrophies?

A

mutations of genes coding for other components of the dystrophin-glycoprotein complex and other muscle proteins

64
Q

What are the components of myosin?

A

Head (S1 chain)

Hinge region of heavy chains

Tail region of heavy chains

65
Q

What is tropomyosin, and what is its role in muscle contraction?

A

The rope like protein that surrounds actin, and blocks the active site until Ca binds

66
Q

What happens to myosin’s affinity for actin when ATP binds?

A

Falls

67
Q

If all cross-bridges in the muscle have ATP bound to them muscle is (contracted or relaxed)?

A

Relaxed

68
Q

What happens to the myosin head when the bound ATP dephosphorylates?

A

Cocks the myosin head into alignment with actin binding site

69
Q

What must occur to the actin/tropomyosin complex before the ADP-myosin complex can bind?

A

Ca has to bind to troponin and move tropomyosin out of the way

70
Q

What triggers the power stroke of the myosin head?

A

Release of the pyrophosphate

71
Q

What happens after the myosin head binds to the active site on the actin filament?

A

ADP is lost (but myosin stays on)

72
Q

What causes the myosin head to become detached from the actin after ADP has left?

A

ATP binding

73
Q

What is the cause of rigor mortis?

A

Lack of ATP to free myosin from actin

74
Q

What happens to the I line as a muscle contracts?

A

Get smaller/disappears

75
Q

What happens to the A band of the sarcomere as a muscle contracts?

A

Stays constant

76
Q

What happens to the H band of the sarcomere as a muscle contracts?

A

Gets smaller

77
Q

How does a muscle cell relax?

A

ATP will help pump out Ca, as well as detach myposin heads from actin

78
Q

A neuromuscular junction is a “safe” synapse. What does this mean?

A

only one action potential in pre-junctional neuron is necessary to cause an action potential in muscle cell.

79
Q

What type of synapse innervates muscle cells?

A

The motor plate

80
Q

How does the action potential spread through a muscle cell (through what structure)?

A

Through T tubules

81
Q

What is the neurotransmitter used at motor plates at the neuromuscular junction?

A

Acetylcholine

82
Q

What does acetylcholine bind to? What does this cause?

A

Acetylcholine receptor, which causes K to go out slightly, but Na to rush in a ton

83
Q

In the triad, where is the action potential? Where is Ca stored?

A

Action potential is an element of the T tubule

Ca is stored in the sarcoplasmic reticulum

84
Q

What are the voltage gated channels in the T tubules that open to allow Ca to rush in?

A

L-type (DHP) channels

85
Q

When the DHC (L-type) channels open, what does this cause in turn?

A

The Ca channels on the sarcoplasmic reticulum side to open

86
Q

The Ca++- release channels on the sarcoplasmic reticulum are also called what?

A

ryanodine receptors.

87
Q

What are the proteins that enable the sarcoplasmic reticulum to pump Ca against its gradient?

A

Calsequestrin and Calreticulin

88
Q

What are the three ways that Ca is pumped out of the cytosol of muscle cells?

A

Pumped into sarcoplasmic reticulum by ATP pumps

Pumped out via Ca pumps

Antiport with Na

89
Q

What is the purpose of phosphocreatine?

A

High energy molecule that can regenerate ATP from ADP in times when ATP demand exceeds supply

90
Q

What is the breakdown product of creatine?

A

Creatinine

91
Q

What is the other source of energy for working muscle besides creatine?

A

Glycogen

92
Q

What is a motor unit?

A

A small group of nerves with the muscles they innervate

93
Q

What is a motor neuron pool?

A

All of the motor units that collectively innervate an entire muscle

94
Q

Muscle that need very fine motor control (such as the eyes) have what type of motor units? (very small or very large)

A

Very small

95
Q

How do muscles achieve graded contraction? (2 ways)

A

Increase/decrease the number of motor units at any one time

Summation effect of action potential -> Ca released before taken back up

96
Q

True or false: There is a very short delay between end of AP and development of muscle tension

A

True

97
Q

Continuous state of full activation of muscle is called what?

A

tetany or tetanization

98
Q

What prevents the heart from reaching tetany?

A

Longer action potential (d/t [Ca])

99
Q

True of false: an action potential in motor neuron will cause AP in all the muscle fibers of that motor unit

A

True

100
Q

What is isometric contraction?

A

When a muscle does not shorten during the contraction

101
Q

What is isotonic contraction?

A

When a muscle does shorten during a contraction but the tension on the muscle remains constant.

102
Q

When using muscles normally, what type of contraction is being used: isotonic or isometric?

A

Both

103
Q

When is the most tension present in a sarcomere?

A

When all the myosin heads are attached to an actin filament

104
Q

What causes the decrease in tension as sarcomeres shorten to their ends?

A

Abutment of the actin filaments

105
Q

When looking at a curve of passive vs total tension, what is the active tension?

A

The difference between the two curves

Physiology (75 decks)

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