Explain the process that occurs in neuromuscular junctions from when the action potential in the pre-synaptic knob to transmission in the next neurone (6 marks).

The action potential in the pre-synaptic neurone causes calcium ion channels to open

This causes calcium ions to diffuse into the neurone, down its concentration gradient

This causes vesicles containing acetylcholine to fuse to the pre-synaptic membrane

Acetylcholine is then released into the synaptic cleft

Acetylcholine diffuses across the cleft and binds to sodium channels on the post-synaptic membrane, opening them

Sodium ions diffuse into the post-synaptic membrane, causing depolarisation and triggering an action potential

Acetylcholinesterase in the synaptic cleft binds to acetylcholine and delivers it back to the pre-synaptic knob to be recycled