Myasthenia Gravis

Question 1

where Ach synthesized?

Answer 1

motor nerve terminal

Question 2

how many (Ach) vesicles are released into synaptic cleft?

Answer 2

150-200

Question 3

proteins involved in fusion and recycling of synaptic vesicles

Answer 3

SNARES

Question 4

what are the 5 subunits of AchRs?

Answer 4

2 alpha
1 gamma
1 beta
1 delta

Question 5

how is agrin able to activate MuSK receptor?

Answer 5

through MASC

Question 6

What can induce AchR clustering?

Answer 6

MuSK through rapsyn

Laminins through alpha, beta dystroglycan and rapsyn`

Question 7

what is the underlying defect of MG?

Answer 7

decrease in number of available acetylcholine receptors at NMJ due to an antibody-mediated autoimmune attack

Question 8

each subunit of AchR is composed of how many transmembrane regions?

Answer 8

4 – M1, M2, M3, M4

Question 9

between ages 50-60, MG is more common in

Answer 9

men

Question 10

between ages 20-30, MG is more common in

Answer 10

women

Question 11

cardinal features of MG

Answer 11

weakness and fatigability

Question 12

MG diagnostic test

Answer 12

anti-achR antibodies

Question 13

autoantibodies associated to MG

Answer 13

autoantibodies to:

anti-achR ab
MuSK (interfere w/ clustering of AChRs)
LRP4
Agrin (normal clustering of ACHRs affected)

Question 14

amount of Ach released per impulse declines on repeated activity

Answer 14

presynaptic rundown

Question 15

cause of transient neonatal MG

Answer 15

placental transfer of maternal AChR to infants of mothers w/ autoimmune MG

TEMPORARY – lasts for only a few weeks

Question 16

Arthrogryposis multiplex congenita

Answer 16

caused by antibody production against fetal gamma subunit of AChR

multiple joint contractures

Question 17

caused by autoantibodies directed against P/Q type calcium channels at motor nerve terminals

Answer 17

lambert-eaton myasthenic disease