Neuro-muscular disorders

Question 1

Skeletal muscle fibers are innervated by?

Answer 1

large,myelinated motor neurons originating form the anterior horn of the spinal cord

Question 2

Where do myelinated fibers originate from ?

Answer 2

anterior horn of the spinal cord

Question 3

Each end of the motor axon branches out into…?

Answer 3

20-1000 thin terminal fibers (terminal unmyelinated)

Question 4

How is the terminal branches of a single motor neuron that innervate muscle fibers called?

Answer 4

motor unit

Question 5

Neuro-muscular junction is formed by?

Answer 5

connection of the axon terminals of the motor neuron with muscle fibers

Question 6

Neuro-muscular junction?

Answer 6

chemical synapse that lies between terminal ends of motor neurons and skeletal muscle fibers

Question 7

Myoneural junction?

Answer 7

where pre-synaptic neurotransmitters like ACh are released to interact with post-synaptic receptors

Question 8

Acetylcholine receptor?

Answer 8

transmemebrane receptor glycoprotein, ligated gated channels anchored to dystrophin-related protein complex

Question 9

AchR heteropentamer?

Answer 9

alpha, beta,epsilon,gamma

Question 10

Which subunit of AChr heteropentamer allows the coupling of the Ach neurotransmitter with the ACh receptor?

Answer 10

alpha

Question 11

What is the ion released by the sarcoplasmic reticulum that is involved in the Ach release?

Answer 11

Ca 2+

Question 12

MuSK?

Answer 12

-essential step in neuromuscular synapse
-initiates postsynaptic differentiation (priming muscle for synapse formation)

Question 13

LRP4?

Answer 13

-stimulates MuSK for postsynaptic differentiation
-receptor of agrin

Question 14

What is the most common neuro-muscular junction disorder?

Answer 14

Myasthenia gravis

Question 15

Myasthenia gravis is an _____________?

Answer 15

antiboy-mediated auto immune disease

Question 16

Antibodies are usually ____________ nicotonic acetylcholine receptor(AChR)?

Answer 16

usually against AChR located in the neuromuscular junction thus reduces the number of AChR and can cause damage to the post-synaptic membrane

Question 17

AChR usually target, __________ subunit?

Answer 17

alpha subunit

Question 18

What happen if there is no binding of ACh to AChR ?

Answer 18

AChR destruction

Question 19

AChR antibodies have antibodies against _______?

Answer 19

MuSK (muscle-specific receptor tyrosine kinase)

Question 20

What are the molecules that the AChR antibodies are against ?

Answer 20

MuSK and LRP4

Question 21

What is a clinical finding in Myasthenia gravis?

Answer 21

-fluctuating, (fatigable) weakness of commonly used muscles

Question 22

Hallmark features of Myasthenia Gravis?

Answer 22

ptosis,
diplopia(double-vision)
dysarthria(muscle of speech are weak thus trouble speaking)
dysphagia(swallowing difficulties)
respiratory/limb muscle weakness

Question 23

What is the 50% of the findings in a patient with Myasthenia Gravis?

Answer 23

ocular findings

Question 24

What are the most disabiling symptoms in Myasthenia Gravis patients?

Answer 24

bulbar symptoms (include dysarthria,dysphagia,facial weakness and weakness of mastication)

Question 25

Does weakness in myasthenia gravis increase or worsen with physical activity?

Answer 25

worsen but improves with rest

Question 26

Myasthenic crisis?

Answer 26

worsening of muscle weakness, resulting in respiratory failure that requires intubation or mechanical ventilation

Question 27

What are some trigger factors that can cause myasthenic crisis?

Answer 27

infection or aspiration

Question 28

What is the most common test to evaluate for Myasthenia gravis?

Answer 28

slow repetetive nerve stimulation

Question 29

What is the first line of immunosuppressive treatment for Myasthenia Gravis?

Answer 29

corticosteroids

Question 30

What are the Lambert-eaton antibodies ?

Answer 30

-antibodies that are against the P/Q-type voltage-gated Ca2+ channels
-cause reduction of neurotransmitter release

Question 31

What are treatment options for Lambert-eaton?

Answer 31

3,4 Diaminopyridine (DAP)
Guanidine hydrochloride