Synaptic transmission in somatic and autonomic nervous system

Question 1

At a neuromuscular junction, where in the nerve cell does the AP arrive?

Answer 1

Presynaptic knob

Question 2

At a neuromuscular junction, what happens when the AP arrives at the presynaptic knob of the nerve cell?

Answer 2

Presynaptic membrane is depolarised, causes voltage-gated calcium ion channels to open

Question 3

At a neuromuscular junction, what does the influx of calcium ions in the nerve cell cause?

Answer 3

Cascade of events is triggered, which results in quanta containing acetylcholine fusing with presynaptic membrane

Question 4

What is a quanta?

Answer 4

Membrane-bound vesicle that contains a neurotransmitter

Question 5

At a neuromuscular junction, how do acetylcholine quanta reach the postsynaptic muscle membrane?

Answer 5

Diffuse across synaptic cleft and acetylcholine molecules bind to acetylcholine/nicotinic receptors (ligand-gated ion channel) on postsynaptic muscle membrane

Question 6

How many acetylcholine quanta are released by one AP?

Answer 6

60 - 10,000

Question 7

At a neuromuscular junction, what happens after acetylcholine binds to nicotinic receptors on the postsynaptic muscle membrane?

Answer 7

Triggers influx of different ions, mostly sodium ions, which depolarises the postsynaptic membrane

Question 8

At a neuromuscular junction, what happens after the postsynaptic muscle membrane is depolarised?

Answer 8

Muscle action potential propagated over the sarcolemma (plasma membrane of muscle cell), down through transverse tubules to inner aspects of muscle fibre