Final answer:
The statement is false; action potentials are typically initiated by voltage-gated Na+ channels, which result in depolarization. Voltage-gated K+ channels are important for repolarization. Voltage-gated Ca2+ channels are involved at the synaptic terminals for neurotransmitter release.
Step-by-step explanation:
The statement that action potentials are usually mediated by voltage-gated Ca2+ channels is false. Action potentials are primarily initiated by the opening of voltage-gated Na+ channels, which leads to the rapid influx of sodium ions and the depolarization of the neuron's membrane.
As the membrane depolarizes, these voltage-gated sodium channels are triggered to open, allowing more sodium ions to enter the cell which propagates the action potential.
Additionally, voltage-gated K+ channels play a key role in the repolarization phase of an action potential. Once the membrane potential reaches its peak, these potassium channels open, and potassium ions rush out of the cell, which helps to restore the resting membrane potential.
While voltage-gated Ca2+ channels also play a significant role in neurotransmission, they are primarily involved in the synaptic transmission process. When an action potential reaches the axon terminal, these calcium channels open and allow calcium ions to enter the presynaptic cell, triggering the release of neurotransmitters into the synaptic cleft.