Question

With the normal extracellular calcium concentration, [Ca₂⁺], when the action potential reaches the axon terminal it triggers?

1) contraction of the axon terminal
2) release of neurotransmitter by exocytosis
3) a chemical reaction where Ca₂⁺ is converted to Mg₂⁺
4) no response

Answer 1

Voltage-gated Ca²+ channels in the axon terminal membrane open in response to the action potential, leading to the release of neurotransmitter by exocytosis.

Step-by-step explanation:

When an action potential reaches the axon terminal, voltage-gated Ca²+ channels in the membrane open. This allows calcium ions (Ca²+) to enter the axon terminal. The increase in Ca²+ concentration inside the axon terminal triggers the release of neurotransmitter by exocytosis into the synaptic cleft.