Question

Imagine you insert a stimulating electrode into a "typical" neuron in your arm, so that you can inject any amount of depolarizing or hyperpolarizing current that you want into the cell. Assume for the sake of this question that doing so will not alter the ionic concentration gradients in your tissue, kill the cell, or damage any of the normal components of the cell. Is there any way that you could create a situation where K^+ ions were diffusing on net from the extracellular fluid into this neuron?

A Yes, that would happen if you injected enough hyperpolarizing current into the cell to drop its Vm below the equilibrium potential of K^+.

B Yes, that would happen if you maintained the cell's Vm between the equilibrium potentials of K^+ and Na^+.

C Yes, that would happen if you injected enough depolarizing current into the cell to raise its Vm above the equilibrium potential of Na^+.

D No, it's not physically possible to favor the movement of K^+ ions in that direction.

Answer 1

Questions

Imagine you insert a stimulating electrode into a "typical" neuron in your arm, so that you can inject any amount of depolarizing or hyperpolarizing current that you want into the cell. Assume for the sake of this question that doing so will not alter the ionic concentration gradients in your tissue, kill the cell, or damage any of the normal components of the cell. Is there any way that you could create a situation where K^+ ions were diffusing on net from the extracellular fluid into this neuron?

Answer... B.. Explanation..

B Yes, that would happen if you maintained the cell's Vm between the equilibrium potentials of K^+ and Na^+.

if the sodium channels are opened, positively charged sodium ions flood into the neuron, and making the inside of the cell momentarily positively charged - the cell is said to be depolarized. This has the effect of opening the potassium channels, allowing potassium ions to leave the cell.