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Physiology > Skeletal muscle > Flashcards

Flashcards in Skeletal muscle Deck (105):
1

What is a sarcolemma?

Plasmalemma for muscle cells

2

What is a sarcomere?

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

3

What is the sarcoplasmic reticulum?

Where Ca is stored

4

What is the transverse tubules (T tubules)?

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

5

What is a muscle fiber?

Synonymous with muscle cell

6

What is a myofibril?

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

7

What is titin?

The protein that hold the thick filaments to the Z disk

8

What is dystrophin?

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

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

9

What is a ryanodine receptor?

The DHP channel located in the Triad

10

What are DHP receptors?

1

11

Which is the actin filament (thin or thick)?

Thin

12

Which is the thick filament?

Myosin

13

What is the Z-disc made of?

1

14

What are cross-bridges?

1

15

What is the sliding filament theory of muscle contraction?

The fact that the thick filaments slide across the thin filaments

16

What is the role of ATP in muscle contraction?

Detaches the myosin from the actin active site

(this is the reason for rigormortis)

17

What is the role of Ca in muscle contraction?

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

18

Which type of muscle is striated?

skeletal

19

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

Cardiac

20

Which type of muscles have a centrally located nucleus?

Smooth

21

What type of connections do intercalated discs have?

Electrical and mechanical (d/t pores)

22

Which type of muscles have multiunit connections to each cell?

Smooth

23

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

Gap junctions for transmission between cells

24

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

Epimysium

25

What is the CT layer around a single fasicle?

Perimysium

26

What is the CT layer around an individual muscle fiber?

Endomysium

27

What are the dominant organelle in muscle cells?

Mito

28

What is the sarcoplasma?

The cytosol for muscle cells

29

What is inside T tubules?

Extracellular fluid

30

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

Sarcolemmas x2 + transverse tubule

allows for conduction of signals from ECF to myofibrils

31

What is the etiology of Duchenne's muscular dystrophy?

An almost total lack of dystrophin

32

What is the etiology of Becker's muscular dystrophy?

Mutated, but still somewhat functional dystrophin

33

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

Heads

34

What is tropomyosin?

The protein that covers the active sites on the actin?

35

What are the proteins that form the troponin complex?

Tnt
TnC
TnI

36

What do the troponins bind?

TnT- tropomyosin
TnC- Ca
TnI-actin

37

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

Loss of phosphate from head (NOT from ATP)

38

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

Nothing much (look at slide)

39

How far do muscle fibers extend?

The length of the muscle

40

What are the two components to the sarcolemma?

Plasma membrane
Transverse tubules

41

What is the outer coat of a sarcolemma made of?

A thin layer of collagen

42

What is the area that is between two Z discs?

sarcomere

43

What are the two attachments of a titin protein molecule?

Z line
Myosin thick filaments

44

What is the sarcotubular system?

The system of transverse tubules and sarcoplasmic reticulum

45

What is the function of the sarcoplasmic system?

Transmits action potential throughout the cell,

46

What is the function of the sarcoplasmic reticulum?

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

47

How does dystrophin add strength to muscles?

connecting fibrils to the ECM

48

What are the two types of striated muscle?

Skeletal and cardiac

49

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

Smooth

50

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

Actin

51

What is the component of the H band?

Myosin

52

What are the components of the A band?

Where myosin and actin overlap + H band

53

Which type of muscles are connected by gap junctions?

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

54

What are the two kinds of smooth muscle?

Multiunit and Unitary

55

Where are nuclei found in skeletal muscle cells?

At the periphery

56

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

Myofibril

57

What are bunches of myofibrils called?

Muscle fibers

58

What are bunches of muscle fibers called?

Fascicles

59

What is the M line?

The central line in the sarcomere

60

What is the cause of familiar dilated cardiomyopathy?

Titin mutation

61

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

Titin mutation

62

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

X-linked recessive

63

What is the cause of the limb-girdle dystrophies?

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

64

What are the components of myosin?

Head (S1 chain)

Hinge region of heavy chains

Tail region of heavy chains

65

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

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

66

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

Falls

67

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

Relaxed

68

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

Cocks the myosin head into alignment with actin binding site

69

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

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

70

What triggers the power stroke of the myosin head?

Release of the pyrophosphate

71

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

ADP is lost (but myosin stays on)

72

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

ATP binding

73

What is the cause of rigor mortis?

Lack of ATP to free myosin from actin

74

What happens to the I line as a muscle contracts?

Get smaller/disappears

75

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

Stays constant

76

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

Gets smaller

77

How does a muscle cell relax?

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

78

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

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

79

What type of synapse innervates muscle cells?

The motor plate

80

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

Through T tubules

81

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

Acetylcholine

82

What does acetylcholine bind to? What does this cause?

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

83

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

Action potential is an element of the T tubule

Ca is stored in the sarcoplasmic reticulum

84

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

L-type (DHP) channels

85

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

The Ca channels on the sarcoplasmic reticulum side to open

86

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

ryanodine receptors.

87

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

Calsequestrin and Calreticulin

88

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

Pumped into sarcoplasmic reticulum by ATP pumps

Pumped out via Ca pumps

Antiport with Na

89

What is the purpose of phosphocreatine?

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

90

What is the breakdown product of creatine?

Creatinine

91

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

Glycogen

92

What is a motor unit?

A small group of nerves with the muscles they innervate

93

What is a motor neuron pool?

All of the motor units that collectively innervate an entire muscle

94

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

Very small

95

How do muscles achieve graded contraction? (2 ways)

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

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

96

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

True

97

Continuous state of full activation of muscle is called what?

tetany or tetanization

98

What prevents the heart from reaching tetany?

Longer action potential (d/t [Ca])

99

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

True

100

What is isometric contraction?

When a muscle does not shorten during the contraction

101

What is isotonic contraction?

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

102

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

Both

103

When is the most tension present in a sarcomere?

When all the myosin heads are attached to an actin filament

104

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

Abutment of the actin filaments

105

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

The difference between the two curves