During the firing of a nerve cell, the membrane potential rises above -70 mV. The equilibrium ratio of the concentration of Cl^- ions in axoplasm to interstitium before the pulse arrives is 0.072. In which direction will the Cl^- ions flow during the passage of the pulse? A)They will flow from interstitium to axoplasm. B)They will flow from axoplasm to interstitium. C)No migration of Cl^- ions takes place. D)As the system is no longer in equilibrium, we cannot use Nernst's equation to determine the direction of flow

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Quizplus · Accepted Answer

During the firing of a nerve cell, the membrane potential becomes less negative (rises above -70 mV), which can lead to a change in the direction of ion flow across the membrane. Given the equilibrium ratio of Cl- ions (represented here as Cl^- for formatting reasons) in axoplasm to interstitium is 0.072, this indicates that under resting conditions, there are more Cl- ions in the interstitium than in the axoplasm. When the membrane potential rises, the electrical gradient that normally helps retain Cl- ions in the interstitium is reduced, potentially reversing or altering the flow of ions. Therefore, Cl- ions will flow from the area of higher concentration (interstitium) to the area of lower concentration (axoplasm) to try to re-establish equilibrium, driven by both the concentration gradient and the change in membrane potential.

During the Firing of a Nerve Cell, the Membrane Potential