Final answer:
Action potentials are facilitated by both voltage-gated and ligand-gated channels. Voltage-gated channels respond to changes in electrical membrane potential, while ligand-gated channels open upon neurotransmitter binding, both contributing to depolarization that leads to action potentials.
Step-by-step explanation:
Action potentials, which are crucial for neural communication, involve the coordinated opening and closing of two primary channels: voltage-gated channels and ligand-gated channels.
Voltage-gated channels are critical in the initiation and propagation of action potentials. These channels respond to changes in the membrane potential. For instance, voltage-gated Na+ channels open when the membrane depolarizes from -70 mV to -55 mV, allowing Na+ ions to rush into the neuron, further depolarizing the membrane. If this depolarization reaches the threshold (-55 mV or beyond), it triggers an action potential.
Ligand-gated channels, on the other hand, open in response to the binding of neurotransmitters to their receptors, which can also contribute to the depolarization of the neuron and may aid in reaching the threshold for an action potential if enough Na+ ions enter the cell.
Leak channels play a role in maintaining the resting membrane potential, but they do not directly contribute to the generation of action potentials. Therefore, the correct answer to the student's question is Both a and c: voltage-gated and ligand-gated channels.