How is an action potential (AP) transmitted across a synapse?

As an action potential (AP) arrives at the synaptic knob and depolarises the presynaptic membrane, voltage-gated Ca2+ channels open, allowing the entry of Ca2+ ions, This caues vesicles (membrane-bound organelle within cytoplasm) containing various neurotransmitters (e.g. acetylcholine) to move towards and fuse with the presynaptic membrane. The neurotransmitters are released, they diffuse across the syanptic cleft and bind to the corresponding receptors on the postsynaptic membrane. This then causes Na+ channels to open, allowing influx of Na+ ions. The postsynaptic membrane depolarises, and an AP is sent down the axon following the synapse once the threshold for AP is reached. When the presynaptic membrane is no longer depolarised, neurotransmitters bound to receptors are broken down by a specific enzyme (e.g. acetylcholinesterase) and the products are recycled.