Question

A polarized neuron in its resting state has A. high potassium & high sodium ion concentratio inside the cell membrane B. High potassium ion concentration on the outside of the cell membrane and high sodium ion concentration on the inside of the cell membrane C. High sodium and high potassium ion concentrations outside the cell membrane D. high sodium and high potassium ion concentrations outside the cell membrane

Answer 1

In a polarized neuron at resting state both Na and K⁺ channels are closed because the K⁺ ions leak into the cell and the membrane is permeable to K⁺ ions 100 times more than normal. The Na channels respond when the part of nerve cell is depolarized. Therefore, at resting state, a neuron contains high sodium and high potassium concentrations inside the cell membrane. Option A is correct.

Depolarization: The membrane becomes less polarized and less negative potential is observed inside the cell than at the resting potential.

Repolarization: The membrane returns to resting potential after depolarization.

Hyperpolarization: The membrane becomes more polarized and becomes more negative inside the cell than at resting potential.

M +20 - e +10 Depolarization (decrease in potential; membrane less negative) r 10 n 20 30 40 t 50 -60 70 Repolarizarion (return to resting potential after depolarization) Hyperpolarization (increase in potential; membrnae more negative) Resting potential 90 (mV) Time (msec) Types of changes in membrane potential