Question

if the membrane potential is +20 mV, will potassium ions try to enter or exit the neuron? why? name a membrane potential where potassium ions will try to enter the neuron

Answer 1

When the membrane potential is +20 mV, potassium ions try to exit the membrane as:

i) During depolarisation, number of Na⁺ ions enter the cell increasing the positive charge more inside than outside. Due to this intracellular repulsions, K⁺ ions start exiting out of the neuron.

ii) Also, K⁺ conductance increases due to opening of potassium channels in response to the changing voltage.

Active transport is the phenomenon responsible for transporting K⁺ inside the cell. The membrane potential at which it happens is very close to the resting membrane potential i.e. -70 mV.

The reason why it happens is because potassium ion concentration is really high inside the cell with a ratio of intracellular potassium to extracellular potassium around 40:1.