Question

When a nerve cell membrane is depolarized by 5 mV

A. Its permeability to sodium increases.

B. Sodium ions move into the cell to cause further depolarization.

C. Potassium ions move outwards down their electro chemical gradient.

D. Chloride ions move inwards down their electro chemical gradient.

E. An action potential is generated.

Answer 1

A. True Depolarization opens sodium channels in the membrane.

B. True Positively charged sodium ions move down their electro chemical gradient making the inside of the fibre more positive.

C. True The fall in membrane potential increases the outward electro chemical gradient for the positively charged potassium ions; their exit tends to stabilize the membrane potential.

D. True The fall in membrane potential increases the inward electro chemical gradient for chloride; this again tends to restore the resting membrane potential.

E. False Not unless it reaches the threshold for **.