Final answer:
The amount of neurotransmitter released is closely related to the total number of action potentials, as each action potential leads to a calcium-triggered release of neurotransmitters from the axon terminal.
Step-by-step explanation:
The total amount of neurotransmitter released at the axon terminal is most directly related to C. the total number of action potentials. Each action potential arriving at the axon terminal triggers the entry of calcium ions (Ca2+) into the neuron through voltage-gated calcium channels. This calcium influx causes synaptic vesicles loaded with neurotransmitters to merge with the presynaptic membrane and release their contents into the synaptic cleft in a process called exocytosis. The neurotransmitter then diffuses across the synapse, binding to receptors on the postsynaptic neuron and potentially initiating a new action potential.
It is important to note that the all-or-none principle states that the amplitude of the action potential is consistent, independent of the intensity of the stimulus that produced it. Thus, the amount of neurotransmitter released is not directly proportional to action potential amplitude but is related to the frequency of action potentials.