Question

Imagine you created a toxin such that when a neuron fired an action potential, the toxin would bind immediately to the sodium-potassium pump at the top of the action potential, but the sodium and potassium channels would still function. What process(es) would be affected?

Answer 1

Maintaining resting potential will be affected. The toxin will bind to the sodium potassium pump at the top of the action potential. It means the toxin will bind when the potential of the cell is almost +40 because the resting potential of the cell is -70 and when a stimulus is applied the depolarization occurs and the voltage reaches upto +40 at peak action potential. After peak action potential repolarization of cell occurs which ends with hyperpolarization and finally resting potential occurs. Depolarization occurs due to entry of 3 sodium ions and leaving of 2 potassium ions via sodium potassium pump. Repolarization occurs due to efflux of potassium ions after attaing peak potential.

If toxin will bind to the sodium potassium pump at the peak it will not bring any change at that point because after attaining peak potential the influx of sodium ions closes and efflux of potassium ions occurs through sodium potassium channel due to concentration gradient. Once hyperpolarization is achieved then influx of sodium ions is required to attain the resting potential but here due to toxin the sodium potassium pump is not working and thus the influx of sodium will not occur and hence the neuronal cell will not attain the resting potential.