Question

In hyperkalemia, the resting membrane potential a. moves farther from 0 millivolts. b. moves closer to 0 millivolts. c. remains unaffected.

Short answer

In hyperkalemia, the resting membrane potential becomes less negative due to the decreased concentration gradient caused by an increased level of potassium ions (K+) in the blood. Therefore, the resting membrane potential moves closer to 0 millivolts, corresponding to option b.

Step-by-step solution

Understand the role of K+ ions in resting membrane potential

The resting membrane potential of a cell is primarily determined by the concentration of K+ ions inside and outside the cell. The resting membrane potential is negative because there are more K+ ions inside the cell than outside, leading to a concentration gradient. This gradient drives K+ ions to flow out of the cell through potassium channels, resulting in a negatively charged interior.

Analyze the effect of hyperkalemia on K+ ion concentration and resting membrane potential

In hyperkalemia, the concentration of K+ ions in the blood increases, which means there are more K+ ions outside the cell. This increased K+ ion concentration outside the cell reduces the concentration gradient between the inside and outside of the cell. Since the gradient is smaller, fewer K+ ions flow out of the cell through potassium channels, causing the resting membrane potential to become less negative.

Relate the change in resting membrane potential to the given options

Now that we understand the effect of hyperkalemia on resting membrane potential, we can analyze the given options: a. moves farther from 0 millivolts: This option implies that the resting membrane potential becomes more negative, which is not what happens in hyperkalemia. So, this option is incorrect. b. moves closer to 0 millivolts: This option implies that resting membrane potential becomes less negative. Based on our analysis, this is the correct answer, as hyperkalemia causes the resting membrane potential to become less negative due to the decreased concentration gradient. c. remains unaffected: This option implies that there is no change in resting membrane potential, which is not the case for hyperkalemia. So, this option is also incorrect.

Conclusion

In hyperkalemia, the resting membrane potential moves closer to 0 millivolts, which corresponds to option b. Thus, the correct answer is b. moves closer to 0 millivolts.