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BRS MUSCULOSKELETAL And RHEUM > Microstructure And Contraction > Flashcards

Microstructure And Contraction Flashcards

1
Q

What type of control is smooth muscle under?

A

Involuntary control

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2
Q

What part of the nervous system does smooth muscle act under?

A

Autonomic nervous system

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3
Q

What type of control is the skeletal muscle under?

A

Voluntary control

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4
Q

What does skeletal muscle do?

A

Bring about movement

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5
Q

What connects bone to muscle

A

A tendon

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6
Q

What are skeletal muscles usually attached to?

A

Bones

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7
Q

What is the microstructure of a muscle?

A

Myofilaments
Myofibril
Myofibre
Fascicles
Muscle

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8
Q

What are muscle fasciculus surrounded by?

A

Perimysium

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9
Q

What are myofibres surrounded by?

A

Endomysium

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10
Q

What surrounded the bundles of muscles fascicles to hold them together?

A

Epimysium

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11
Q

What is the nucleus state of muscle fibers?

A

Multinucleate

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12
Q

What is the plasma membrane that covers the myofibres called?

A

Sarcolemma

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13
Q

What is found in the sarcoplasm?

A

myoglobin and mitochondria

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14
Q

What is the sarcoplasmic reticulum?

A

Network of fluid filled tubules

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15
Q

What is one repeating unit of a myofibril called?

A

A sarcomere

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16
Q

What two proteins do myofibril consist of?

A

Actin and myosin

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17
Q

What is the thin filament called.

A

Actin

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18
Q

Thick filaments are

A

Myosin

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19
Q

What makes up the dark portion of the light and dark bands?

A

Myosin

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20
Q

What separates sarcomeres?

A

Dense Z protein discs

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21
Q

What is the I band?

A

The light bands with thin actin filaments

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22
Q

Do myofilaments extend the length of the myofibres?

A

No

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23
Q

What causes muscle contraction?

A

Movement of actin filaments over the myosin filaments, which shortens the length of the sarcomere

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24
Q

How many heads does myosin have?

A

Two globular heads

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25
Q

What forms the single tail of myosin?

A

Two alpha helices

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26
Q

What forms a myosin filament?

A

The tails of several hundred molecules

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27
Q

What two other molecules do actin filaments contain?

A

Troponin and tropomyosin

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28
Q

What shape are actin molecules twisted into?

A

Helix

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29
Q

What happens to the I band when the muscle contracts?

A

Shortens

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30
Q

What happens to the A band during contraction?

A

Stays the same length

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31
Q

What is the A band?

A

The dark band

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32
Q

What happens to the distance between the Z discs during muscle contraction?

A

Shortens

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33
Q

Describe the initiation of muscle contraction?

A
  1. Action potential arrives at end of motor neurone
  2. Voltage gated Ca2+ channels open
  3. Ca2+ enters pre-synaptic terminal
  4. Triggers the exosytosis of vesicles
  5. ACh released into the cleft
  6. Binds to receptors
  7. Generates action potential
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34
Q

How is ACh broken down?

A

Using acetylcholine esterase

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35
Q

Describe the activation of muscle contraction?

A
  1. AP propagates along surface and into T tubules
  2. dihydropyridine receptors in T tubule membranes sense change in voltage and changes shape of the protein linked to ryanoidine receptor
  3. Ryanodine receptor then opens and releases Ca2+ out into space around filaments
  4. Ca2+ binds to troponin
  5. Causes tropomyosin to move, exposing the myosin head binding site
  6. Ca2+ is then actively transported into the sarcoplasmic reticulum
  7. Charged myosin head binds to exposed site on actin filament
  8. This binding causes the myosin head to pívot pulling the actin filament towards center if sarcomere
  9. ATP binds which causes the myosin head to be released
  10. ATP hydrolysis provides energy to recharge the myosin head
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36
Q

What receptor detects the change in voltage when an action potential arrives at the T tubule

A

Dihydropyridine

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37
Q

What is the DHP receptor bound to?

A

Ryanodine receptor

38
Q

What does Ca2+ bind to on the actin filament?

A

Troponin

39
Q

What is covering the myosin binding site?

A

Tropomyosin

40
Q

What is the power stroke?

A

The pivoting of the the myosin head to slide the actin chain over the myosin filament

41
Q

What binds to the myosin head to charge the myosin head to move?

A

ATP

42
Q

What is used to “recharge” the myosin head for more contraction?

A

ADP hydrolysis to make ATP

43
Q

Describe the neural control of muscle contraction?

A

Upper motor neurone in the brain to lower motor neurones in the brainstem or spinal cord

44
Q

What is a motor unit?

A

A single motor neurone together with all the fibers that it innervates

45
Q

How many muscle fibers do each motor neurone supple on average?

A

600

46
Q

What happens when a single motor neurone is stimulated?

A

All the muscle fibers in that motor unit will contract

47
Q

What is the best innervation ratio for high levels of fine control?

A

Neurones which innervate fewer muscle fibers

48
Q

What is a type one motor unit?

A

Slow

49
Q

What are type IIa muscle fibers?

A

Fast, fatigue resistant

50
Q

What are type IIB motor units?

A

Fast and fatiguable

51
Q

Which motor units have small cell body diameter?

A

Slow, type I

52
Q

Which motor unit type have thicker axons?

A

Type IIA and IIB

53
Q

What is the size difference in dendritic trees of the different motor units ?

A

Larger dendritic trees in Type IIA and Type IIB, smaller in type I

54
Q

How are muscle fibers distributed throughout the muscle?

A

Randomly

55
Q

Which muscle fiber type are rich in myoglobin?

A

Slow type I and type IIA (fast, fatigue resistant)

56
Q

Which type of muscle fibers are used for aerobic activity?

A

Slow twitch fibres

57
Q

Which muscle fibre type are used for anaerobic functions?

A

Fast and fatiguable muscle fibers

58
Q

Which muscles have a high proportion of slow twitch fibers?

A

Muscles involved in postural control

59
Q

What three factors are motor units classified by?

A

Amount of tension, speed of contraction and fatiguability

60
Q

What are the two mechanisms by which the brain regulates the forces that a single muscle produces?

A

Recruitment and rate coding

61
Q

Describe the recruitment mechanism?

A

The more motor units that are recruited, the larger the size of the force

62
Q

What is the size principle?

A

The smaller motor units are recruited first

63
Q

What happens during recruitment when more forces is needed?

A

More muscle units are recruited

64
Q

Describe the rate coding principle?

A

The firing rate down the motor neurones to the motor unit changes as more force is needed to be produced

65
Q

What is ramp contraction (summation)?

A

When the force of contraction increases over time due to more recruitment

66
Q

How does recruitment regulate the stimulation of motor units?

A

By regulating the number of motor units that are recruited

67
Q

Which motor unit is the first to be derecruited?

A

The motor unit which was recruited last - therefore this motor unit will be the one largest in size

68
Q

What are neurotrophic factors?

A

Type of growth factor which prevent neuronal death and promote growth of neurones after injury

69
Q

What does the motor unit and fibre characteristics depend on?

A

The nerve which innervates them

70
Q

What happens to fast and slow twitch muscle fibers is they are cross innervated?

A

The fast becomes slow and slow becomes fast

71
Q

What are the three main types of muscle contraction?

A

Isometric
Concentric
Eccentric

72
Q

What is isometric contraction?

A

When the muscle unit produces forces but doesn’t change length

73
Q

What is a concentric muscle contraction?

A

When the muscle shortened in order to produce movement

74
Q

What is eccentric contraction?

A

When force is produced but the muscle fibers is getting longer

75
Q

What is an example of eccentric muscle contraction?

A

When a person is lifting up a dumbbell which is too heavy for them

76
Q

Which type of muscle contraction produces the most force?

A

Eccentric

77
Q

Which type of muscle contraction can damage and tear muscle fibers?

A

Eccentric

78
Q

Following training, what is the most common type of muscle fiber change?

A

Type IIB to IIA (FAST FATIGUABLE TO FATIGUE RESISTANT)

79
Q

What can cause a change from type 1 to type 2 muscle fibers?

A

Severe deconditioning or spinal cord injury

80
Q

What type of fibers are found in aged muscle?

A

Larger proportion of type 1 fibers

81
Q

What provides evidence for the larger proportion of type 1 fibers in aged muscle?

A

Slower contraction time

82
Q

What shift in muscle fibers type is associated with microgravity?

A

Slow to fast

83
Q

Why is there a slow to fast shift in microgravity?

A

Less need for postural muscle innervation (slow)

84
Q

Where is the sarcolemma in relation to the endomysium?

A

The sarcolemma lies under the endomysium which surrounds the muscle fibre

85
Q

What is meant by a pennate arrangement of muscle fibres?

A

When muscle fibres are placed at angles to the tendon

86
Q

What is a unipennate arrangement of muscle fibres?

A

When the muscle is going in the same direction as the tendon

87
Q

What is a bipennate arrangement of muscle fibres?

A

When the muscle fibres are spread out in two direction from the tendon

88
Q

What is a multipennate arrangement of muscle fibres?

A

When there are many tendons and many fibres

89
Q

What is a parallel muscle fibre?

A

When the muscle fibre is straight across

90
Q

What is meant by a fusiform muscle fibre?

A

When the middle of the fibre is thicker and larger in size than the two outer edges

91
Q

What are the three shapes of muscle fibres?

A

parallel
fusiform
triangular

BRS MUSCULOSKELETAL And RHEUM (17 decks)

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