Final answer:
In triggering an action potential, Na+ ions create a positive feedback loop by increasing the depolarization, leading to further opening of sodium channels. The sodium/potassium pump is activated by the action potential and is necessary for restoring the resting potential.
Step-by-step explanation:
In the first phase of triggering an action potential in a neuron, Na+ ions flow into the cell, which triggers a positive feedback loop. This is because the influx of sodium ions depolarizes the membrane, and as a result, more voltage-gated sodium channels open, allowing even more Na+ ions to enter the cell. This amplifies the depolarization, further opening sodium channels along the axon in a self-propagating manner until the action potential propagates down the length of the neuron.
The correct statement regarding the effect on the flux of sodium ions across the membrane when the electric potential difference falls below threshold voltage and an action potential is created is a positive feedback loop, or option E) B and C. This means that option B is the correct justification, as it states that the voltage-gated sodium channels open in response to sodium influx, which allows more sodium to enter through the channels, perpetuating the depolarization signal. Additionally, the sodium/potassium pump, which restores the resting potential after an action potential, is activated by the action potential itself and requires energy to function.