Neuromuscular junction

11 important questions on Neuromuscular junction

What is excitation-contracting coupling?

Successfull transmission leads to contracting of the muscle cell

Which proteins are involved in fusion of ACh vesicles with the presynaptic membrane?

SNARE proteins attach vesicles to the presynaptic membrane
Synaptotagmin makes the connection tighter

Which proteins cluster the AChR?

MuSK and LRP4
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What is the effect of muscular diseases that result in too low EPP?

Increasing muscle weakness (harder to contract) and eventually paralysis

What is the quantal content?

Number of ACh quanta (vesicles) released in response to a presynaptic AP

--> n ACh quanta/pulse

What is the safety factor?

Ratio between supra-threshold EPP (A) and firing threshold (B) --> A/B

--> factor decreases with muscle diseases

What is the effect of disturbed NMJ?

Weakness/paralysis
Spontaneous activity
Cramps

What are causes of NMJ disorders?

Auto-immunity (mainly)
mutation in encoding gene
intoxication

Name some examples of NMJ disorders

Myasthenia gravis
Lambert-Eaton myasthenic syndrome
Congenital myasthenic syndromes
Neuromyotonia
Miller Fisher syndrome
Inherited calcium channelopathies

What is the problem in Lambert-Eaton?

Anti-calcium channel antibodies

How can mouse models be used to analyze NMJ dysfunction?

- hanging wire test = motor coordination/strenght
- horizontal rods test = motor coordinatino/strenght
- whole-body plethysmography = measurement of respiration pattern
- grip strenght test = muscle strenght test
- inverted mesh hanging test = fatigable muscle strenght
- EMG = stimulation and recording of the muscle AP
- dissected muscle nerve preparations
- Ex vivo NMJ elecrophysiology

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