NMJ disoreders

Question 1

what is motor unit

Answer 1

one motor neuron and the muscle fibers it innervates

Question 2

what happens when AP

Answer 2

all fibers activated

Question 3

what happens at NMJ

Answer 3

AP>Ca in pre-syn>Ach release>binding to nicotinic>Na channels open>muscle

Question 4

what is myasthenia gravis

Answer 4

IgG antibody against nicotinic receptor

Question 5

what do antibodies do (2)

Answer 5

1. block Ach binding

2. attract complement for AchR destruction

Question 6

2 factors related to MA onset

Answer 6

1. genetics

2. age > 50 (women get younger)

Question 7

what is potential origin of autoimmunity

Answer 7

1. thymoma in 10%

2. thymus hyperplasia in 70%

Question 8

4 clinical signs of MA

Answer 8

1. fatiguability
2. Proximal>distal
3. ocular weakness
4. bulbar weakness (CN9-12)

Question 9

what is safety factor

Answer 9

release more Ach than needed for synapse

Question 10

2 special tests for MA

Answer 10

1. edrophonium - AchE inhibitor - should get better

2. ice pack test - cold inhibs AchE

Question 11

what is MA crisis

Answer 11

resp failure due to muscle weakness

Question 12

what is lambert eaton disease

Answer 12

IgG antibodies against pre-synaptic Ca channels

Question 13

what is association with lambert eaton

Answer 13

50% malignancy, 80% ar small cell lung

Question 14

4 clinical signs in lambert eaton

Answer 14

1. post-exercise facilitation
2. gradual leg weakness proximal>distal
3. autonomic dysfunction
4. minimal ocular/bulbar