Describe the events that take place at the synapse that enable transmission of a nerve impulse.

An action potential arrives at the synapse, triggering Ca2+ channels to open. This in turn triggers vesicles holding neurotransmitter to fuse with the presynaptic membrane, releasing the neurotransmitter into the synaptic cleft. The neurotransmitter binds to receptors on the postsynaptic membrane and triggers them, initiating an impulse on the postsynaptic membrane. Leftover neurotransmitter is either taken back up by the presynaptic membrane or degraded by enzymes in the synaptic cleft.