Final answer:
The FALSE statement regarding a neuronal action potential is that the opening of Cl- channels on a neuron will depolarize the cell.
Step-by-step explanation:
The FALSE statement regarding a neuronal action potential is d. The opening of Cl- channels on a neuron will depolarize the cell.
The rising phase of a neuronal action potential is indeed caused by Na+ influx. When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated Na+ channels, allowing Na+ ions to enter the cell.
The falling phase of a neuronal action potential is caused by K+ efflux. After the depolarization phase, voltage-gated K+ channels inactivate and open, allowing K+ ions to leave the cell, which repolarizes the membrane.
The influx of Ca2+ into synaptic knobs (terminals) induces exocytosis of neurotransmitters. When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated Ca2+ channels. The influx of Ca2+ ions initiates a signaling cascade that causes synaptic vesicles, containing neurotransmitter molecules, to fuse with the presynaptic membrane.
Therefore, option d, which states that the opening of Cl- channels on a neuron will depolarize the cell, is false because Cl- channels do not play a role in depolarizing the cell during an action potential. Instead, they are involved in maintaining the resting membrane potential.