Final answer:
Calcium flows into the axon terminal through voltage-gated calcium channels due to a concentration gradient, leading to the release of neurotransmitters via exocytosis, which is crucial for neural communication.
Step-by-step explanation:
After the voltage-gated calcium channel is opened, calcium flows through the channels into the axon terminal due to a concentration gradient. There is a higher concentration of Ca2+ ions outside the neuron than inside. When voltage-gated Ca2+ channels open as a result of the action potential depolarizing the axon terminal, Ca2+ flows into the cell, using the process of diffusion to balance the concentration on both sides of the membrane.
The influx of Ca2+ inside the axon terminal is crucial for neurotransmitter release. These calcium ions bind to proteins associated with synaptic vesicles, triggering vesicles to merge with the presynaptic membrane and release their neurotransmitters into the synaptic cleft through the process of exocytosis. This is a critical step in neural communication as it allows the chemical signal, in the form of neurotransmitters, to be passed onto the next neuron, initiating or inhibiting an action potential.