Alterations in Skeletal Muscle Function Flashcards Preview

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Flashcards in Alterations in Skeletal Muscle Function Deck (84):
1

What are the functions of skeletal muscle?

#NAME?

2

How can skeletal muscle function be modified?

- Remodelling of muscles
- Alterations of neuromuscular transmission
- Muscular dystrophies 
- Other myopathies

3

What can happen to the contractile proteins actin and myosin?

They can increase and decrease in nuber

4

When does the remodelling of muscles occur?

Continual

5

How long does it take to replace a contractile protein?

2 weeks

6

What happens if destruction > replacement?

Atrophy

7

What happens if replacement > destruction?

Hypertrophy

8

Why does skeletal muscle change with exercise?

Metabolic adaptation

9

What happens to skeletal muscle with exercise?

- 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

10

Does exercise cause hyperplasia?

No

11

Give an example of a high intensity activity?

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

12

What is the effect of high intensity activity?

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

13

What can high intensity activity lead to?

Hypertrophy

14

Give an example of an endurance exercise

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

15

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

It increases endurance, but without hypertrophy

16

What does endurance exercise stimulate?

Synthesis of mitochondrial proteins and vascular changes

17

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

Allows for greater oxygen utilisation

18

What does endurance exercise result in a shift to?

Oxidative metabolism of lipids

19

What can lead to disuse atrophy?

- Bed rest
- Limb immobilisation 
- Sendentry behaviour

20

What happens in disuse atrophy?

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

21

At what age does muscle atrophy occur?

30+

22

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

50%

23

What is the loss of muscle mass with ageing called?

Sarcopenia

24

What can muscle atrophy with age lead to?

Problems with temperature regulation

25

How can muscle atrophy with age lead to hypothermia?

Not enough muscle mass to generate heat themselves

26

What is denervation atrophy known as?

Neurogenic muscular atrophy

27

What are the signs of lower motor neurone legions?

#NAME?

28

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

Within 3 months

29

What happens in a muscle with spinal muscular atrophy?

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

30

What causes an increase in muscle length?

Sustained stretching

31

What happens when muscles lengthen?

#NAME?

32

What changes of neurology occur in adjustment of muscle length?

- Pain
- Stretch response 
- Stretch reflex

33

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

Change in connective tissue alignment

34

What reduces the length of muscle?

Immobilisation

35

What are the steps in neuromuscular transmission?

- 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

Where are nicotinic receptors located?

On folded end-plate regions

37

What does the depolarisation of muscle following neuromuscular transmission cause?

Release of calcium ions from SR, therefore muscle contraction

38

How is ACh terminated in neuromuscular transmission?

Acetylcholinesterase

39

What happens at high motor neurone firing rates?

ACh release decreases by 25%

40

What needs to be true of ACh receptors?

They must be occupied

41

Give an example of a neuromuscular junction disorder?

Myasthenia Gravis

42

What causes Myasthenia Gravis?

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

43

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

#NAME?

44

What are the symptoms of Myasthenia Gravis?

- Fatiguability 
- Sudden falling
- Ptosis
- Double vision 
- Effected by general state of health, e.g. fatigue and emotion

45

What causes the fatiguability and sudden falling in Myasthenia Gravis?

Sudden ACh release

46

What is ptosis?

Drooping upper eyelids

47

How to the symptoms of Myasthenia Gravis change over time?

They fluctuate

48

What is the treatment for Myasthenia Gravis?

- Acetylcholinesterase inhibitors
- Immune suppressants
- Plasmapheresis 
- Thyrectomy

49

What does plasmapheresis do?

Remove harmful antibodies from patients serum

50

Give 2 toxins that inhibit neuronal Na + channel

- Tetrodotoxin 
- Saxitoxin

51

What toxin inhibits Ca 2+  channel?

α-Conotoxin

52

What toxin inhibits K +  channel?

Dendrotoxin

53

Give 2 toxins that inhibit ACh release?

#NAME?

54

Give 2 toxins that inhibit acetylcholinesterase

- Physostigmine 
- DFP

55

Give 3 toxins that inhibit the muscle Na +  channel

- Tetrodotoxin
- Saxitoxin
- µ-Conotoxin

56

Give 2 toxins that stimulate AChR channel?

- Acetylcholine 
- Nicotine

57

Give 2 toxins that inhibit the AChR channel?

- d-Tubocurarine 
- α-Bungarotoxin

58

What are the two main causes of muscular dystrophies?

#NAME?

59

Give 8 types of muscular dystrophy

- Duchenne type 
- Becker type 
- Emery-Dreifus 
- Limb gurdle
- Facioscapulohumeral 
- Distal
- Occulopharyngeal 
- Congenital Mersonin Deficiency

60

Where does Duchenne and Becker type muscular dystrophy affect?

- Upper legs
- Calves
- Neck
- Shoulders
- Upper arms 
- Pectoral

61

What causes Duchenne type muscular dystrophy?

Complete absence of dystrophin

62

What causes Becker type muscular dystrophy?

Altered truncated dystrophin

63

Where does Emery-Dreifus muscular dystrophy affect?

#NAME?

64

Where does limb gurdle muscular dystrophy affect?

- Upper arms
- Shoulders
- Pectoral 
- Upper legs

65

What causes limb gurdle muscular dystrophy?

Deficiency of sarcoglycans

66

Where does facioscapulohumeral muscular dystrophy affect?

#NAME?

67

Where does distal muscular dystrophy affect?

#NAME?

68

Where does occulopharyngeal muscular dystrophy affect?

#NAME?

69

What causes Congenital Mersonin Deficiency?

50% deficiency of merosin

70

What are the consequences of protein abnormality?

- 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

When does Duchenne muscular dystrophy first become apparent?

Early onset

72

What is the sign of Duchenne muscular dystrophy?

Gower’s sign

73

What is Gower’s sign?

Pushing on knees to give power

74

What is meant by contractures?

Imbalance between agonist and antagonistic muscles

75

How is Duchenne muscular dystrophy treated?

Steroid therapies

76

What is being done to help with Duchenne muscular dystrophies?

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

77

What can skeletal muscle disorders be caused by?

- Denervation 
- Myopathies

78

What is the root of denervation disorders?

Neurological causes

79

What are myopathies?

Primary muscle diseases

80

Give 5 types of myopathies

- Inflammatory
- Electrolyte imbalances
- Thyrotoxicosis
- Hypoparathyroidism 
- Channelopathies

81

Give 3 examples of inflammatory myopathies

- Polymyositis 
- Myalgia 
- Influenza

82

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

Cramps

83

What can the result of thyrotoxicosis be?

Increased basal metabolic rate and protein catabolism

84

Give an example of a channelopathy

Malignant hyperthermia