Disorders of the neuromuscular junction and muscle Flashcards
(87 cards)
What are the disorders of muscle?
Myopathies
Myositis
Myotonic dystrophy
What may be seen in LMN disorders?
Weakness
Low tone
Fasciculations
Skeletal muscle fibres are innervated by _____ ______ whose cell _____ arise in the ______ horn of the spinal cord
Skeletal muscle fibres are innervated by motor neurons whose cell bodies arise in the ventral horn of the spinal cord
The terminal portion of these motor neurones give rise to very fine _________ that run along the muscle cell.
The synapses formed between motor neurons and muscle are called the _____ ___ plate
The terminal portion of these motor neurones give rise to very fine projections that run along the muscle cell.
The synapses formed between motor neurons and muscle are called the motor end plate
A single motor neurone may control ____ ______ cells but each muscle cell response to ____ ____ motor neuron
A single motor neurone may control many muscle cells but each muscle cell response to only one motor neuron
What is found on the end of the motor neurone?
ACh vesicles
What receptor are present on the muscle ?
ACh receptors
______ ______ moves along the nerve, _____ gated ______ channels open allowing influx of _____. Vesicles of _____ ______ are released into ______ ____.
action potential moves along the nerve, voltage gated calcium channels open allowing influx of calcium. Vesicles of acetyl choline are released into synaptic cleft.
____ _____ diffuses across the _____ ____. The _______ receptor opens and renders the membrane permeable to __/_ ions.
The ________ starts an ____ potential at the ____ ___ ___
Acetyl choline diffuses across the synaptic cleft. The acetylcholine receptor opens and renders the membrane permeable to Na/K ions.
The depolarisation starts an action potential at the motor end plate
__________ splits acetylcholine into _____ and ______ which is then sequestered into _______ _____
Acetylcholinesterase splits acetylcholine into acetate and choline which is then sequestered into presynaptic vesicles
What is curare?
d tubocurarine
A plant which occupies the same position on the ACh receptor but does not open ion channel
What does curare result in?
No muscle contraction- so no respiration
When is curare toxic?
IV or IM (1-15mins)
How does novichok work?
Inhibits cholinesterase
What conditions cause problems at the presynaptic motor neurone?
Abnormality of calcium, sodium or magnesium
Botulism
Lambert eaton myastheniac syndrome
Where is clostridium botulinum found?
In soil
What are the common mechanisms of becoming infected with botulinum clostridium?
Food and wounds can become infected.
IV drug users- black tar heroine
What does botulinum clostridium do?
Cleaves presynaptic proteins involved in vesicle formation and blocks vesicle docking with the presynaptic membrane
What are the symptoms of botulinum clostridium infection?
Rapid onset weakness without sensory loss/ Some medical and cosmetic uses)
What happens in LEMS?
Antibodies to presynaptic calcium channels leads to less vesicle release.
What is associated with Lambert eaton myasthenia syndrome?
Strong association with underlying small cell carcinoma.
What can Lambert eaton syndrome be treated with?
3-4 diaminopyridine
Myasthenia gravis is a ________ disorder, it is the _____ common disorder of the NMJ.
Myasthenia gravis is a postsynaptic disorder, it is the most common disorder of the NMJ.
What is the pathophysiology of MG?
Antibodies to acetylcholine receptors (AChR)
Recuded number of ACh receptors and flattening of endplate folds
Transmission becomes inefficient
