Final answer:
Given a resting potential of -70mV, Na+ ions will flow into the neuron due to the concentration and electrical gradients despite a negative driving force, leading to depolarization of the neuron and movement of the membrane potential toward zero.
Step-by-step explanation:
If the resting potential of a neuron is -70mV and the driving force for a Na+ ion is negative, it means that the inside of the cell is negatively charged relative to the outside. Since Na+ ions are positively charged and there is a higher concentration of these ions outside the cell, under normal conditions, Na+ ions will flow into the cell when channels are open. This flow is due to the concentration gradient, where Na+ seeks to equalize the concentration inside and outside of the cell, and is also influenced by the electrical gradient, as positive charges are attracted to the more negatively charged interior.
Even though the driving force mentioned is negative, this typically refers to the electrical driving force; so the direction of the sodium flow would still be into the cell until the charge potential reaches equilibrium. The entry of Na+ causes the inside of the cell to become less negative, a process referred to as depolarization, and moves the membrane potential closer to zero.