What is the role of calcium at the synaptic terminal? what is the role of calcium at the synaptic terminal? calcium enters the synaptic terminal, permitting water to enter, increasing hydrostatic pressure, and forcing neurotransmitter out of the terminal into the synapse. depolarization of the synaptic terminals by an invading action potential opens voltage-gated calcium channels at the terminal, thus permitting diffusion of calcium out of the synaptic terminal. calcium, like sodium, is out of both ionic and electrical equilibrium. therefore, it counteracts the loss of free energy following depolarization of the synaptic terminal. depolarization of the synaptic terminals by an invading action potential releases intracellular calcium stores or allows calcium channels to open to allow calcium to enter the synaptic terminal from the extracellular environment, thus permitting neurotransmitter release.