Flashcards in NMJ and muscle pathologies Deck (51)
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1
Symptoms of LMN disorders?
Weak
Low tone
Fasciculations
2
What innervated skeletal muscle fibres?
Motor neurones whose cell bodies arise in the ventral horn of the spinal cord
3
What is the motor end plate?
Synapses formed between motor neurons and the muscle
4
What is a motor unit?
A single motor neurone and all of the muscle fibres it innervates
5
What occurs when an action potential reaches the nerve?
Ca 2+ channels open
Vesicles of ACh are released into the synaptic cleft
ACh receptor opens and renders the membrane permeable to Na/K+ ions
Depolarisation starts an action potential at the motor end plate
6
What is the action of acetylcholinesterase?
Breaks up ACh into acetate and choline
7
What happens to choline in the synaptic cleft?
Sequestered into presynaptic vesicles
8
How does botulism affect the presynaptic membrane?
Cleaves presynaptic proteins involved in vesicle formation and blocks vesicle docking with the presynaptic membrane
9
What are the symptoms of botulism toxin?
Rapid onset weakness WITHOUT sensory loss
10
What is the pathogenesis of Lambert Eaton Myasthenic Syndrome?
Antibodies to presynaptic calcium channels leading to vesicle release
Strong assoc with small cell lung carcinoma
11
What is the treatment for LEMS?
3-4 diaminopyridine
12
What is the pathogenesis of myasthenia gravis?
Autoimmune antibodies to AChR resulting a reduced number of functioning receptors leading to muscle weakness and fatigability
Flattening of endplate folds
Even with normal ACh; transmission becomes inefficient
13
What is the role of the thymus in myasthenia?
75% have hyperplasia or thymoma
14
What is the epidemiology of myasthenia gravis?
Occurs at any age; 2 peaks of incidence
Females in 3rd decade
Males in 6/7th decade
Female:male ration 3:2
15
What are the clinical features of myasthenia?
Fluctuating weakness throughout the day; tends to be best in the morning
Extraocular weakness
Facial and bulbar weakness
Limb weakness is proximal
16
What is the treatment for myasthenia?
Acetylcholinesterase inhibitor; pyridostigmine
IVIg in acute emergencies
Thymectomy
17
What immune modulating drugs are used in myasthenia?
Steroids
Azathioprine
Mycophenolate
Emergency; plasma exchange or immunoglobulin
18
What drug should be avoided in myasthenia?
GENTAMICIN
Lots of antibiotics CI, lots of anaesthetic drugs are CI
19
What do most people with myasthenia die from?
Resp failure
Aspiration pneumonia
Immunosuppression SE in the elderly
Co-morbid
20
What are the different types of muscle fibres?
Type 1; slow oxidative; resist fatigue, myoglobin, RED
Type 2a; fast oxidative; aerobic metabolism
Type 2b; fast glycolytic, easily fatigued
21
What is a fasciculation?
Visible, fast, fine, spontaneous twitch
22
Why do fasciculations occur?
Healthy muscle; stress, caffeine, fatigue
Denervated muscle which becomes hyperexcitable
23
What are fasciculations a sign of?
MND
24
What is myotonia?
Failure of muscle relaxation after use
Chloride channel issues
25
What are the Si/Sy of muscle disease?
Myalgia
Muscle weakness
Wasting
Hyporeflexia
26
What can cause a head drop?
Myopathy
Myositis
MND
27
What muscles are commonly weak in muscle disease?
Proximal leg
Shoulder girdle
Neck weakness
28
What are immune mediated muscle weaknesses?
Dermatomyositis
Polymyoisitis
29
What are inherited muscle disorders?
Muscular dystrophies
Limb girdle muscular dystrophies
Myotonic dystrophy
30
