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Musculoskeletal > Physiology of Skeletal Muscle > Flashcards

Physiology of Skeletal Muscle Flashcards

1
Q

What are the three types of muscle in the body? Give an example of each

A

Cardiac - heart

Smooth - GI

Skeletal - Leg

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2
Q

The three types of muscle tissue are capable of developing TXXXX and causing MXXXX through CXXXX

A

The three types of muscle tissue are capable of developing tension and causing movement through contraction

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3
Q

Which muscles are striated?

A

Skeletal Muscle Cardiac Muscle

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4
Q

Which muscles are not striated?

A

Smooth Muscles

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5
Q

What causes striations in muscle?

A

Alternate bands of Myosin and Actin MYOSIN = Dark coloured filaments Actin = Light

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6
Q

Dark or Light coloured filaments? - Myosin - Actin

A

Myosin = Dark Actin = Light

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7
Q

Thick or Thin Filaments? - Myosin - Actin

A

Myosin = Thick Actin = Light

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8
Q

Describe the colour and thickness of Myosin?

A

Dark Colour Thick Filaments

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9
Q

Describe the colour and thickness of Actin?

A

Light Colour Thin Filaments

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10
Q

Which muscles are voluntary? Which are involuntary?

A

Skeletal Muscle is Voluntary Smooth Muscle and Cardiac are Involuntary

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11
Q

Which nervous system innervates the Skeletal Muscles?

A

Somatic Nervous System Therefore voluntary

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12
Q

Which nervous system innervates the Smooth Muscles?

A

Autonomic Nervous System Therefore involuntary

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13
Q

Which nervous system innervates the cardiac muscle?

A

Autonomic nervous System therefore involuntary

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14
Q

What are the physiological functions of skeletal muscles?

A

Maintain Posture Allow Movement Respiratory Movement Heat Production Contribute to whole body metabolism

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15
Q

How are skeletal muscle fibres organised?

A

Skeletal muscle fibres are organised in MOTOR UNITS

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16
Q

What are motor units composed of?

A

They contain ONE single alpha motor neurone and all the skeletal muscle fibres it innervates

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17
Q

Describe what happens when one alpha motor neurone is stimulated?

A

This causes stimulation of all the skeletal muscle fibres it innervates

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18
Q

What determines the number of muscle fibres per motor unit?

A

The function of the muscle determines the number of muscle fibres per motor unit Fine movement muscles (Eg: Eyes) have fewer muscle fibres per motor unit Powerful muscles (e.g: Thighs) have more muscle fibres per motor unit

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19
Q

In a muscle that valued presicion over power, how many muscle fibres would there be per motor unit?

A

Low Number

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20
Q

In a muscle that valued power over precision, how many muscle fibres would there be per motor unit?

A

High Number

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21
Q

In skeletal muscle, what is the levels of organisation? Biggest to Largest

A

Whole Muscle Muscle Fibre (One Cell) Myofibril Sarcomere Myosin and Actin

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22
Q

What is the Sarcomere?

A

The sarcomere is the functional unit of skeletal muscle

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23
Q

What mechanisms initiate skeletal muscle contractions?

A

Neurogenic Mechanisms (Nervous System)

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24
Q

In skeletal muscle contraction, where is Ca2+ released from?

A

Sarcoplasmic Reticulum

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25
Q

In skeletal muscle contraction, what initiates Ca2+ release?

A

Action potential spreads down the T tubules

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26
Q

What happens after Ca2+ is released?

A

It binds to ACTIN and prevents tropomyosin from binding to Actin. This pushes tropomyosin to the side and allows the active binding sites on actin to be exposed

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27
Q

What happens after Ca2+ has bonded to its target?

A

Myosin cross bridges attach to Actin They pull actin filaments to the centre of the Sarcomere This is driven by ATP CONTRACTION OCCURS

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28
Q

What drives Myosin pulling Actin filaments?

A

ATP

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29
Q

What happens after muscle contraction?

A

Ca2+ is taken up by the sarcoplasmic reticulum when the action potential stops

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30
Q

What happens after action potential stops?

A

Ca2+ uptake Tropomyosin binds back to Actin Relaxation of muscle

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31
Q

What are Myofibrils?

A

These are specialised contractile intracellular structures They have bands of actin and myosin

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32
Q

What are sarcomeres?

A

Within each cell, actin and myosin are arranged into sarcomeres. These are the functional units of muscle

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33
Q

What is a functional unit?

A

A functional unit is the smallest component capable of performing all of the functions of the organ

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34
Q

Where would you find a sarcomere?

A

Between two Z Lines

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35
Q

How is muscle tension produced?

A

By the sliding of actin filaments on myosin filaments

36
Q

What is the transmitter at the neuromuscular junction?

A

Acetylcholine

37
Q

Skeletal Muscle tension depends on two factors; What are they?

A

Number of Muscle fibres contracting within the muscle

Tension developed by each contracting muscle fibre

38
Q

What is motor unit recruitment?

A

This is when more motor units are stimulated to increase the strength of contraction

39
Q

Describe the effect one motor unit could have on many muscle fibres in terms of contraction?

A

One motor unit can cause simulataneous contraction of many muscle fibres

40
Q

What does motor unit recruitment help prevent?

A

Motor unit recruitment helps prevent fatigue

41
Q

In skeletal muscle activity, which is longer - the action potential or the resulting twitch?

A

The resulting twitch is much longer than the action potential

42
Q

Describe how (in reference to twitches) you can make the contraction stronger?

A

By summating (adding/joining) twitches, you can increase the force of contraction This is done by repeated stimulation of skeletal muscle

43
Q

Describe the resulting twitch from one action potential?

A

One single twitch

44
Q

Describe the resulting twitch from two separate action potentials?

A

Two single twitches

45
Q

Describe the resulting twitch from two action potentials that are very close together?

A

The muscle doesn’t have time to fully relax The twitches are summated and therefore stronger contraction

46
Q

Describe the resulting twitch from many action potentials that are very close together?

A

The muscle doesn’t have time to relax Causes maximum sustained contraction Called TETANUS

47
Q

What is tetanus?

A

This is the maximum sustained contraction of skeletal muscle Caused by high frequency action potentials

48
Q

What muscles can/cannot be tetanized?

A

Skeletal Cardiac cannot

49
Q

How useful is a single twitch?

A

Produces little tension Does not bring about useful skeletal muscle movement

50
Q

How useful is a summated twitch?

A

Produces tension Allows for some useful skeletal muscle movement

51
Q

How useful is tentanized twitch?

A

Produces maximum tension Allows for lots of useful movement

52
Q

Describe the relationship between tension and frequency?

A

As the frequency of action potentials increases, the tension increases

53
Q

What length must muscle be at for maximal tension?

A

Optimal Length

54
Q

When must the muscle be at the optimal length?

A

Before the onset of contraction

55
Q

What is the resting muscle length?

A

Approximately the optimal length

56
Q

What are the two types of skeletal muscle contraction>

A

Isotonic Isometric

57
Q

Describe the two types of skeletal muscle contraction

A

Isotonic is used for movement Muscle tension remains constant as the muscle length changes Isometric is used for holding objects still Muscle tension builds as the muscle length remains constant

58
Q

How is the tension transmitted to bone?

A

Via the elastic components of the muscles

59
Q

What influences the activity of the motor unit?

A

Wide variety of inputs Influenced by the brain and many different receptors

60
Q

What is the main causes of impaired skeletal muscle function?

A
  • Intrinsic muscle disease - Disease of the Neuromuscular Junction - Disease of the lower motor neurone - Disruption of inputs to motor unit
61
Q

Describe some causes of intrinsic muscle disease?

A

Acquired Myopathies (Inflammatory, Endocrine, Toxic) Genetic Myopathies (Congenital, Degernative, Abnormal Ion Channels)

62
Q

What is a reflex?

A

A stereotyped response to a specific stimulus

63
Q

Why is it important to know the neural pathways of reflexes?

A

It is important to know the neural pathways of reflexes to allow you to locate lesions in the motor system

64
Q

Reflex actions are A) Simplest B) Most complex C) Averagely complex form of coordinated movement

A

Reflex actions are the simplest form of coordinated movement

65
Q

Describe the stretch reflex?

A

This is a negative feedback mechanism that resists passive changes in the muscle length to maintain optimal resting muscle length

66
Q

What does the stretch reflex help with?

A

Helps us to maintain posture (Eg: When walking)

67
Q

In the stretch reflex, what is the sensor?

A

The muscle spindle

68
Q

In the stretch reflex, what happens when stretch is detected?

A

Muscle spindle detects stretch This causes increased firing in the afferent neurons Impulse is transferred to alpha motor neurons Activation of reflux causes contraction of stretched muscle

69
Q

What are muscle spindles?

A

These are the sensory receptors for the stretch reflex They are a collection of specialised muscle fibres

70
Q

What are the two names for the different types of muscle fibres?

A

Intrafusal Fibres = Muscle Spindle Extrafusal Fibres = Ordinary Muscle Fibres

71
Q

What are the effectors neurons that supply muscle spindles?

A

Gamma Motor Neurons

72
Q

What are the sensory nerve endings of the muscle spindles called?

A

Annulospindal Fibres

73
Q

Are all skeletal muscle types the same? If no, how do they differ?

A

No Differ in - ATP formation - Fatigue Resistance - Activity of Myosin ATPase

74
Q

What are the ATP pathways?

A

Glycolysis Oxidative Phosphorylation Transfer of high energy phosphate from Creatinine Phosphate to ATP

75
Q

Out the of the ATP pathways, which: - Is the fastest? - Produces the most glucose?

A

Creatinine phosphate is the fastest Oxidative Phosphorylation produces the most glucose

76
Q

What are the three types of skeletal muscle fibres?

A

Type 1 = Slow Oxidative Type 2a = Fast Oxidative Type 2x = Fast Glycolytic

77
Q

Describe Type 1a Skeletal Muscle Fibres - ATP - Speed - Myosin ATPase - Fatigue - Colour

A

Produces lots of ATP Slow Low Myosin ATPase activity Higher Resistance to fatigue Red

78
Q

Describe Type 2x Skeletal Muscle Fibres - ATP - Speed - Myosin ATPase - Fatigue - Colour

A

Less ATP Very Fast High Myosin ATPase activity Lower resistance to fatigue White coloured

79
Q

Describe when the Type 1A muscle fibres are used?

A

Prolonged low intensity activity Eg: Walking

80
Q

Describe when the Type 2A muscle fibres are used?

A

Prolonged moderated intensity activity Eg: jogging

81
Q

Describe when the Type 2X musclbe fibres are used?

A

Short internal, high intensity activity Eg: Sprinting

82
Q

Name the investigations used for muscle disease?

A

Electromyography (EMG) Nerve Conduction Studies Muscle Enzymes

83
Q

Describe EMG?

A

Electrodes detect the presence of muscle activity Records frequency and amplitude of impulses Not specific and not diagnostic Can be used to confirm muscular problem and not neurological

84
Q

Describe Nerve Conduction Studies?

A

Determines the functional integrity (working ability) of peripheral nerves

85
Q

Describe Muscle Enzymes?

A

Specific muscle enzymes (Eg: Creatinine Kinase CK) can be looked for to show muscle damage

Musculoskeletal (23 decks)

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