Question

One of the pills that Ji takes for high blood pressure caused his blood K+ level to decrease from 4.5 mM to 2.5 mM. What happens to the resting membrane potential of his liver cells? (Circle all that are correct.)

decreases

increases

does not change

becomes more negative

becomes less negative

fires an action potential

depolarizes

hyperpolarizes

repolarizes

Answer 1

A decrease in blood potassium levels from 4.5 mM to 2.5 mM leads to the depolarization of the resting membrane potential, making it less negative. This is because the potassium gradient is essential for maintaining the resting potential, and a lower external K+ concentration reduces this gradient.

Step-by-step explanation:

When Ji's blood potassium (K+) level decreases from 4.5 mM to 2.5 mM, it affects his liver cells' resting membrane potential. The resting membrane potential is mainly established by the concentration gradient of potassium ions moving out of the cell, which is now compromised. Since a lower K+ concentration in the blood would reduce the concentration gradient, there would be less movement of K+ out of the cell, causing the inside of the cell to become less negative.

This would result in the resting membrane potential becoming less negative, or in other words, the membrane would depolarize. However, this does not necessarily mean the cell would fire an action potential, as depolarization would need to reach a certain threshold, which may not happen in liver cells. Thus, the correct options to circle would be that the resting membrane potential increases (becomes less negative) and depolarizes.