Neuro-muscular disorders Flashcards
Skeletal muscle fibers are innervated by?
large,myelinated motor neurons originating form the anterior horn of the spinal cord
Where do myelinated fibers originate from ?
anterior horn of the spinal cord
Each end of the motor axon branches out into…?
20-1000 thin terminal fibers (terminal unmyelinated)
How is the terminal branches of a single motor neuron that innervate muscle fibers called?
motor unit
Neuro-muscular junction is formed by?
connection of the axon terminals of the motor neuron with muscle fibers
Neuro-muscular junction?
chemical synapse that lies between terminal ends of motor neurons and skeletal muscle fibers
Myoneural junction?
where pre-synaptic neurotransmitters like ACh are released to interact with post-synaptic receptors
Acetylcholine receptor?
transmemebrane receptor glycoprotein, ligated gated channels anchored to dystrophin-related protein complex
AchR heteropentamer?
alpha, beta,epsilon,gamma
Which subunit of AChr heteropentamer allows the coupling of the Ach neurotransmitter with the ACh receptor?
alpha
What is the ion released by the sarcoplasmic reticulum that is involved in the Ach release?
Ca 2+
MuSK?
-essential step in neuromuscular synapse
-initiates postsynaptic differentiation (priming muscle for synapse formation)
LRP4?
-stimulates MuSK for postsynaptic differentiation
-receptor of agrin
What is the most common neuro-muscular junction disorder?
Myasthenia gravis
Myasthenia gravis is an _____________?
antiboy-mediated auto immune disease
Antibodies are usually ____________ nicotonic acetylcholine receptor(AChR)?
usually against AChR located in the neuromuscular junction thus reduces the number of AChR and can cause damage to the post-synaptic membrane
AChR usually target, __________ subunit?
alpha subunit
What happen if there is no binding of ACh to AChR ?
AChR destruction
AChR antibodies have antibodies against _______?
MuSK (muscle-specific receptor tyrosine kinase)
What are the molecules that the AChR antibodies are against ?
MuSK and LRP4
What is a clinical finding in Myasthenia gravis?
-fluctuating, (fatigable) weakness of commonly used muscles
Hallmark features of Myasthenia Gravis?
ptosis,
diplopia(double-vision)
dysarthria(muscle of speech are weak thus trouble speaking)
dysphagia(swallowing difficulties)
respiratory/limb muscle weakness
What is the 50% of the findings in a patient with Myasthenia Gravis?
ocular findings
What are the most disabiling symptoms in Myasthenia Gravis patients?
bulbar symptoms (include dysarthria,dysphagia,facial weakness and weakness of mastication)
