Question

A neuron is poisoned with a chemical, which is an inhibitor of the Na⁺-K⁺ ATPase. Explain what would happen to the resting membrane potential (RMP) of the cell (will it depolarize, hyperpolarize or remain the same). In your answer,

a.)identify the three factors that determine RMP in a neuron,

b.) identify whether each factor causes membrane potential to be more or less negative, and

c.) explain whether or not the chemical would affect each factor.

Answer 1

Na- K - pump is responsible for influx of 2 potassium into the cell and efflux of three sodium out of the cell so as to maintain chemical gradient across the cell.

This increase Na concentration outside the cell and K concentration inside the cell. Inhibition of Na-K pump by a chemical will interfere the movement of these ions across the cell. And hence more sodium will be present inside the cell making the inside of the cell more positve. This results in depolarizaton state.

Factors responsible for maintenance of RMP Are

1) Na ion gradient across the cell

2) potassium ion gradient

3) permeability of these ions

Sodium ion gradient is decreased when the cell is stimulated resulting in inflow of sodium into the cell. This entry of the sodium will cause depolarizaton.

Potassium ions are more inside the cell than outside. Soon after following depolarizaton, potassium channels get opened causing exit of these ions out of the cell and hence positive ions move outside the cell causing repolarization.

Chemical by binding to Na-K pump will inhibit the pump and then the gradient of these ions across the cell will get lost. This result in persistent depolarizaton.