Question

Exocytosis of neurotransmitter from the axon terminal is triggered by an increase in the intracellular concentration of?

1) Na⁺
2) K⁺
3) Ca₂⁺
4) none of these

Answer 1

The exocytosis of neurotransmitter from the axon terminal is triggered by an increase in the intracellular concentration of Ca²+.

Step-by-step explanation:

The exocytosis of neurotransmitter from the axon terminal is triggered by an increase in the intracellular concentration of Ca²+. When an action potential reaches the axon terminal, voltage-gated calcium (Ca²+) channels open, allowing calcium ions to enter the cell.

The increase in calcium concentration inside the end bulb facilitates the fusion of synaptic vesicles containing neurotransmitter molecules with the presynaptic membrane, leading to the release of neurotransmitters into the synaptic cleft through exocytosis.