Question

Anissa is working in an electrophysiology lab. She has isolated an excitable patch of membrane in the cell, generates one action potential but then finds that she cannot generate any action potentials, even with the supre-threshold stimulation. Which of the following statements could most likely account for this scenario?

a) The cell Anissa is recording does not contain voltage gated Na+ channels
b) The intracellular concentration of K+ ions is now higher than the extracellular concentration

c) The membrane contains voltage gated K+ channels that produce after-hyperpolarizations
d) The voltage gated Na+ channels in the membrane are all permanently inactivated

Answer 1

d) The voltage gated Na+ channels in the membrane are all permanently inactivated.

• If the cell Anissa is recording does not contain voltage gated Na+ channels, then she will not be getting the first action potential as well. Hence, wrong option.
• The intracellular concentration of K+ ions higher than the extracellular concentration is a normal resting membrane scenario. Generation of action potential depends on movement of Na+ ions across the membrane. Hence, wrong option.
• After-hyperpolarization falls under relative refractory period and hence stimulations with intensity greater than the previous impulse will produce action potential. But, it is given that even supra-threshold stimulation cannot produce action potential. Hence, wrong option.

Hence, we can say voltage gated Na+ channels in the membrane are all permanently inactivated so that no impulses are able to generate action potential.