When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob. Describe how.

Membrane depolarisation arrives at the pre-synpase and causes Ca2+ voltage-gated channels to open. This allows Ca2+ ions to diffuse in the presynapse via the activated Ca2+ channels. Ca2+ influx in the presynapse induces vesicles carrying the neurotransmitter to fuse with the presynaptic membrane and release their content in the synaptic knob.