<P> The neurotransmitter molecule packages ( vesicles ) are created within the neuron , then travel down the axon to the distal axon terminal where they sit docked . Calcium ions then trigger a biochemical cascade which results in vesicles fusing with the presynaptic membrane and releasing their contents to the synaptic cleft within 180 μs of calcium entry . Triggered by the binding of the calcium ions , the synaptic vesicle proteins begin to move apart , resulting in the creation of a fusion pore . The presence of the pore allows for the release of neurotransmitter into the synaptic cleft . The process occurring at the axon terminal is exocytosis , which a cell uses to exude secretory vesicles out of the cell membrane . These membrane - bound vesicles contain soluble proteins to be secreted to the extracellular environment , as well as membrane proteins and lipids that are sent to become components of the cell membrane . Exocytosis in neuronal chemical synapses is Ca triggered and serves interneuronal signalling . </P>
what type of ion channels is necessary for the function of the axon and the axon terminal
Calcium