Final answer:
Acetylcholinesterase destroys acetylcholine after its release to prevent continuous stimulation of the postsynaptic membrane.
Step-by-step explanation:
Acetylcholinesterase (AChE) plays an important role in neuronal transmission across a synapse by destroying the neurotransmitter acetylcholine (ACh) shortly after its release by the axonal endings. This prevents continuous stimulation of the postsynaptic membrane and allows for the synaptic cleft to be ready for another signal. Inhibitors of acetylcholinesterase can increase neurotransmission by blocking the enzyme's activity, leading to higher levels of ACh in the synaptic cleft.