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Z OLD Tissues of the Body > Alterations in Skeletal Muscle Function > Flashcards

Alterations in Skeletal Muscle Function Flashcards

1
Q

What are the functions of skeletal muscle?

A

NAME?

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2
Q

How can skeletal muscle function be modified?

A
  • Remodelling of muscles
  • Alterations of neuromuscular transmission
  • Muscular dystrophies
  • Other myopathies
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3
Q

What can happen to the contractile proteins actin and myosin?

A

They can increase and decrease in nuber

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4
Q

When does the remodelling of muscles occur?

A

Continual

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5
Q

How long does it take to replace a contractile protein?

A

2 weeks

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6
Q

What happens if destruction > replacement?

A

Atrophy

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7
Q

What happens if replacement > destruction?

A

Hypertrophy

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8
Q

Why does skeletal muscle change with exercise?

A

Metabolic adaptation

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9
Q

What happens to skeletal muscle with exercise?

A
  • Sarcoplasmic reticulum swells
  • Increased volume of mitochondria
  • Increased Z band width
  • Increased ATPase
  • Increased density of T tubule systems
  • Increased in no. of contractile protein
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10
Q

Does exercise cause hyperplasia?

A

No

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11
Q

Give an example of a high intensity activity?

A

Weight lifting, e.g. 70-90% intensity, short duration, modest frequency

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12
Q

What is the effect of high intensity activity?

A

Stimulates contractile protein synthesis, fatter muscle fibres and larger muscles, which increases muscle mass and stength

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13
Q

What can high intensity activity lead to?

A

Hypertrophy

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14
Q

Give an example of an endurance exercise

A

Jogging e.g. low intensity, for a longer duration, 5 times a week

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15
Q

What is the advantage of endurance exercise over high intensity exercise?

A

It increases endurance, but without hypertrophy

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16
Q

What does endurance exercise stimulate?

A

Synthesis of mitochondrial proteins and vascular changes

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17
Q

What is the result of the stimulation of mitochondrial proteins and vascular changes in endurance exercise?

A

Allows for greater oxygen utilisation

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18
Q

What does endurance exercise result in a shift to?

A

Oxidative metabolism of lipids

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19
Q

What can lead to disuse atrophy?

A
  • Bed rest
  • Limb immobilisation
  • Sendentry behaviour
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20
Q

What happens in disuse atrophy?

A

Loss of protein leading to reduced fibre diameter, leading to loss of power

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21
Q

At what age does muscle atrophy occur?

A

30+

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22
Q

How much muscle mass has been lost my the age of 80?

A

50%

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23
Q

What is the loss of muscle mass with ageing called?

A

Sarcopenia

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24
Q

What can muscle atrophy with age lead to?

A

Problems with temperature regulation

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25
Q

How can muscle atrophy with age lead to hypothermia?

A

Not enough muscle mass to generate heat themselves

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26
Q

What is denervation atrophy known as?

A

Neurogenic muscular atrophy

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27
Q

What are the signs of lower motor neurone legions?

A

NAME?

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28
Q

How quickly does reinnervation need to occur for recovery from denervation atrophy?

A

Within 3 months

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29
Q

What happens in a muscle with spinal muscular atrophy?

A

The atrophic fibres are small, angulated and brightly eosinophilic, with an apparent increase in number of nuclei

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30
Q

What causes an increase in muscle length?

A

Sustained stretching

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31
Q

What happens when muscles lengthen?

A

NAME?

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32
Q

What changes of neurology occur in adjustment of muscle length?

A
  • Pain
  • Stretch response
  • Stretch reflex
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33
Q

What changes to viscoelastic properties occur in adjustment of muscle length?

A

Change in connective tissue alignment

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34
Q

What reduces the length of muscle?

A

Immobilisation

35
Q

What are the steps in neuromuscular transmission?

A
  • Opening of presynaptic voltage-dependant calcium channels, causing ACh release
  • ACh binds to nicotinic receptor
  • Binding of ACh to its receptor opens the sodium channel
  • Sodium entry depolarises muscle
36
Q

Where are nicotinic receptors located?

A

On folded end-plate regions

37
Q

What does the depolarisation of muscle following neuromuscular transmission cause?

A

Release of calcium ions from SR, therefore muscle contraction

38
Q

How is ACh terminated in neuromuscular transmission?

A

Acetylcholinesterase

39
Q

What happens at high motor neurone firing rates?

A

ACh release decreases by 25%

40
Q

What needs to be true of ACh receptors?

A

They must be occupied

41
Q

Give an example of a neuromuscular junction disorder?

A

Myasthenia Gravis

42
Q

What causes Myasthenia Gravis?

A

Autoimmune destruction of the end patch ACh receptors (IgA antibodies to AChRs)

43
Q

What is the result of the autoimmune destruction in Myasthenia Gravis?

44
Q

What are the symptoms of Myasthenia Gravis?

A
  • Fatiguability
  • Sudden falling
  • Ptosis
  • Double vision
  • Effected by general state of health, e.g. fatigue and emotion
45
Q

What causes the fatiguability and sudden falling in Myasthenia Gravis?

A

Sudden ACh release

46
Q

What is ptosis?

A

Drooping upper eyelids

47
Q

How to the symptoms of Myasthenia Gravis change over time?

A

They fluctuate

48
Q

What is the treatment for Myasthenia Gravis?

A
  • Acetylcholinesterase inhibitors
  • Immune suppressants
  • Plasmapheresis
  • Thyrectomy
49
Q

What does plasmapheresis do?

A

Remove harmful antibodies from patients serum

50
Q

Give 2 toxins that inhibit neuronal Na + channel

A
  • Tetrodotoxin
  • Saxitoxin
51
Q

What toxin inhibits Ca 2+ channel?

A

α-Conotoxin

52
Q

What toxin inhibits K + channel?

A

Dendrotoxin

53
Q

Give 2 toxins that inhibit ACh release?

54
Q

Give 2 toxins that inhibit acetylcholinesterase

A
  • Physostigmine
  • DFP
55
Q

Give 3 toxins that inhibit the muscle Na + channel

A
  • Tetrodotoxin
  • Saxitoxin
  • µ-Conotoxin
56
Q

Give 2 toxins that stimulate AChR channel?

A
  • Acetylcholine
  • Nicotine
57
Q

Give 2 toxins that inhibit the AChR channel?

A
  • d-Tubocurarine
  • α-Bungarotoxin
58
Q

What are the two main causes of muscular dystrophies?

59
Q

Give 8 types of muscular dystrophy

A
  • Duchenne type
  • Becker type
  • Emery-Dreifus
  • Limb gurdle
  • Facioscapulohumeral
  • Distal
  • Occulopharyngeal
  • Congenital Mersonin Deficiency
60
Q

Where does Duchenne and Becker type muscular dystrophy affect?

A
  • Upper legs
  • Calves
  • Neck
  • Shoulders
  • Upper arms
  • Pectoral
61
Q

What causes Duchenne type muscular dystrophy?

A

Complete absence of dystrophin

62
Q

What causes Becker type muscular dystrophy?

A

Altered truncated dystrophin

63
Q

Where does Emery-Dreifus muscular dystrophy affect?

64
Q

Where does limb gurdle muscular dystrophy affect?

A
  • Upper arms
  • Shoulders
  • Pectoral
  • Upper legs
65
Q

What causes limb gurdle muscular dystrophy?

A

Deficiency of sarcoglycans

66
Q

Where does facioscapulohumeral muscular dystrophy affect?

67
Q

Where does distal muscular dystrophy affect?

68
Q

Where does occulopharyngeal muscular dystrophy affect?

69
Q

What causes Congenital Mersonin Deficiency?

A

50% deficiency of merosin

70
Q

What are the consequences of protein abnormality?

A
  • Muscle fibres tear themselves apart on contraction
  • Enzyme creatine (phospho)kinase liberated into serum
  • Calcium enters cell causing cell death
  • Pseudohypertrophy (swelling), before fat and connective tissue replace muscle fibres
71
Q

When does Duchenne muscular dystrophy first become apparent?

A

Early onset

72
Q

What is the sign of Duchenne muscular dystrophy?

A

Gower’s sign

73
Q

What is Gower’s sign?

A

Pushing on knees to give power

74
Q

What is meant by contractures?

A

Imbalance between agonist and antagonistic muscles

75
Q

How is Duchenne muscular dystrophy treated?

A

Steroid therapies

76
Q

What is being done to help with Duchenne muscular dystrophies?

A

Genetic research, e.g. into gene therapy, stem cells etc

77
Q

What can skeletal muscle disorders be caused by?

A
  • Denervation
  • Myopathies
78
Q

What is the root of denervation disorders?

A

Neurological causes

79
Q

What are myopathies?

A

Primary muscle diseases

80
Q

Give 5 types of myopathies

A
  • Inflammatory
  • Electrolyte imbalances
  • Thyrotoxicosis
  • Hypoparathyroidism
  • Channelopathies
81
Q

Give 3 examples of inflammatory myopathies

A
  • Polymyositis
  • Myalgia
  • Influenza
82
Q

Give an example of a myopathy caused by an electrolyte imbalance?

83
Q

What can the result of thyrotoxicosis be?

A

Increased basal metabolic rate and protein catabolism

84
Q

Give an example of a channelopathy

A

Malignant hyperthermia

Z OLD Tissues of the Body (19 decks)

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