The Neuromuscular Junction

Question 1

What is the neuromuscular junction a synapse between?

Answer 1

• Motoneurone
• Muscle cell

Question 2

How does Ca2+ enter the presynaptic terminal in a NMJ?

Answer 2

Depolarisation opens voltage-gated Ca2+ channels

Question 3

Function of Ca2+ in the NMJ

Answer 3

Causes vesicles containing ACh to fuse with the presynaptic membrane and release it

Question 4

How does Ca2+ cause vesicle fusion?

Answer 4

Ca2+ binds to synaptotagmin (sensor) and conformational change triggers vesicle fusion

Question 5

What does ACh bind to?

Answer 5

Nicotinic receptors

Question 6

What type of receptor is a nicotinic receptor?

Answer 6

Ionotropic (ligand-gated channel)

Question 7

Resting potential and end-plate potential of muscle

Answer 7

• RP = -90mV
• EPP = -20mV

Question 8

What is the function of the EPP?

Answer 8

Causes an action potential in muscle

Question 9

What does the action potential travel down in a muscle?

Answer 9

Transverse tubules (T tubules)

Question 10

What do T tubules allow?

Answer 10

Transmission of AP deep into muscle fibre to separate myofibrils

Question 11

How long is ACh bound to the nAChR?

Answer 11

1ms

Question 12

What hydrolyses ACh after it is released back into the synaptic cleft?

Answer 12

Acetylcholinesterase