Question

The release of chemical messenger from synaptic vesicles is under the influence of which of these ion(s)?

• A. Cl-
• B. Fe++ and s++
• C. Ca ++
• D. Mg++ and Sr++

Answer 1

Answer: (C)

Ca ++

A. Ca++

Reason: During the transmission of nerve impulses, when an impulse arrives at the synaptic knob of the axon, it depolarizes the presynaptic membrane and increases its permeability to calcium ions ($C{a}^{++}$). $C{a}^{++}$ ions now pass into the synaptic knob from the synaptic cleft, via voltage-gated channels. This causes a sudden rise in the cytosolic concentration of $C{a}^{++}$, which in turn, causes the release of a chemical, known as neurotransmitter substance (e.g. Acetylcholine), from small synaptic vesicles present there into the synaptic cleft by exocytosis through the presynaptic membrane. So the correct option is C.