An action potential arrives at the pre synaptic membrane which initiates the opening of Ca2+ channels. The influx of Ca2+ ions will cause vesicles containing neurotransmitters to fuse with the pre-synaptic membrane. The neurotransmitters will leave the pre-synaptic membrane via exocytosis and diffuse across the synaptic clef. The neurotransmitters will bind to complementary receptors on the post-synaptic membrane. Binding of neurotransmitter to the receptor cause the ligand-gated Na+ channels on the post-synaptic membrane to open , allowing Na+ to move into the post-synaptic membrane. The entry of enough Na+ ions will depolarise the post synaptic membrane and an action potential will be generated.