M2 L13

Question 1

nicotinic Ach receptors

Answer 1

• five subunits
• each unit has 4x transmembrane domains
• muscle nAchR subunits slightly different to neuronal
• subunits surround pore in membrane
• pore is normally closed

Question 2

what goes through nAchR

Answer 2

Na+ and K+
causes depolarisation

Question 3

what happens to nAchR when exposed to Ach for too long

Answer 3

desensitisation, channel remains closed

Question 4

what is myasthenia gravis

Answer 4

• autoimmune disease of the NMJ
• antibodies to nAchR
• reduced NMJ function -> weakness

Question 5

why do myasthenia gravis symptoms come on in sustained contraction and how is it treated

Answer 5

• rapid sequence of AP = slight depletion of Ach pool = less Ach released per AP
• when receptors reduced this can cause muscle failure
• AchE blockers treat this by preventing Ach breakdown, allowing more receptors to be activated as Ach build up

Question 6

how is ACh synthesised

Answer 6

acetyl CoA + Choline
-(choline acetyltransferase/ChAT)->
Ach + CoA

Question 7

how is Ach broken down

Answer 7

Ach
-(acetylcholineesterase/AChE)->
Acetic acid + Choline