Zoology - Neural Control and Coordination Question with Solution | TestHub

When an impulse arrives at the synaptic knob of the axon, it depolarizes the presynaptic membrane and increases its permeability to calcium ions $\left({\mathrm{Ca}}^{2+}\right).{\mathrm{Ca}}^{2+}$ ions from the synaptic cleft pass into the synaptic knob via voltagegated channels. Sudden rise in the cytosolic concentration of ${\mathrm{Ca}}^{2+}$, causes the release of a chemical, called neurotransmitter substance, from small synaptic vesicles present there into the synaptic cleft by exocytosis through the presynaptic membrane.