The diagram illustrates the structures and processes involved in a chemical cholinergic synapse.
Which of the following statements correctly describes the roles of the labeled structures during synaptic transmission?
The arrival of an action potential depolarises the presynaptic membrane, opening structure XXX to allow Ca2+\text{Ca}^{2+}Ca2+ ions to diffuse down their electrochemical gradient into the synaptic knob.
Structure YYY releases acetylcholine into the synaptic cleft via active transport, requiring carrier proteins and ATP.
Enzyme ZZZ hydrolyses the neurotransmitter to ensure the postsynaptic ligand-gated channels remain open, sustaining continuous depolarisation.
Blocking structure XXX with a neurotoxin would increase the accumulation of neurotransmitter in the synaptic cleft, leading to muscle spasms.
