complete each sentence with the correct word

An action potential reaches the axon terminal causing ______________ to open.



voltage-gated [tex]\mathrm{Na}^{+}[/tex]channels
sodium lons
threshold
ligand-gated ion channels
motor end plate
exocytosis
voltage-gated [tex]\mathrm{Ca}^{2+}[/tex] channels
voltage-gated [tex]\mathrm{K}^{+}[/tex]channels
diffusion
calcium ions