Question

If the resting axon's membrane becomes more permeable to potassium ions,

A) the inside of the membrane will become more positively charged.
B) the membrane will depolarize more rapidly.
C) it will take a stimulus of larger magnitude to initiate an action potential.
D) the hyperpolarization at the end of the action potential will not occur.

Answer 1

Increasing the permeability of a resting axon's membrane to potassium ions will necessitate a larger stimulus to initiate an action potential due to a further negative shift in membrane potential and increased hyperpolarization.

Step-by-step explanation:

If the resting axon's membrane becomes more permeable to potassium ions, then it will take a stimulus of larger magnitude to initiate an action potential. This is because as the membrane becomes more permeable to potassium ions, more K+ will flow out of the neuron, which will increase the negativity of the interior of the neuron relative to the outside.

As a result, the resting membrane potential will move further away from the threshold that must be reached to depolarize the neuron and generate an action potential. This increased difference makes it harder for any subsequent stimuli to depolarize the neuron to the threshold required to fire an action potential, thereby necessitating a larger stimulus.

During a normal action potential, the sodium-potassium pump helps to restore the resting potential after the hyperpolarization phase, which temporarily makes the membrane potential more negative than the resting state. This hyperpolarization occurs due to the efflux of K+ ions from the cell. If the membrane were to become more permeable to these ions, it would exacerbate this effect, thus increasing the hyperpolarizing overshoot and making it even more challenging for a new action potential to be initiated.

Answer 2

Increasing the permeability of a resting axon's membrane to potassium ions will necessitate a larger stimulus to initiate an action potential due to a further negative shift in membrane potential and increased hyperpolarization.

Step-by-step explanation:

If the resting axon's membrane becomes more permeable to potassium ions, then it will take a stimulus of larger magnitude to initiate an action potential. This is because as the membrane becomes more permeable to potassium ions, more K+ will flow out of the neuron, which will increase the negativity of the interior of the neuron relative to the outside.

As a result, the resting membrane potential will move further away from the threshold that must be reached to depolarize the neuron and generate an action potential. This increased difference makes it harder for any subsequent stimuli to depolarize the neuron to the threshold required to fire an action potential, thereby necessitating a larger stimulus.

During a normal action potential, the sodium-potassium pump helps to restore the resting potential after the hyperpolarization phase, which temporarily makes the membrane potential more negative than the resting state. This hyperpolarization occurs due to the efflux of K+ ions from the cell. If the membrane were to become more permeable to these ions, it would exacerbate this effect, thus increasing the hyperpolarizing overshoot and making it even more challenging for a new action potential to be initiated.