A 63-year-old man is dehydrated after 3 days of alcohol abuse. His serum sodium level has increased from a normal value of 140 to 147 mEq/L. The resting membrane potential of a typical neuron was −80 millivolts before dehydration. What is the most likely resting membrane potential of a typical neuron after the dehydration, assuming no change in resting sodium conductance?
A)−72 millivolts
B)−74 millivolts
C)−80 millivolts
D)−88 millivolts
E)−98 millivolts

Question

Quizplus · Accepted Answer

The resting membrane potential of a typical neuron is primarily determined by the concentration of potassium ions inside and outside the cell, not by sodium ions. Therefore, changes in serum sodium levels, such as those caused by dehydration, would not significantly alter the resting membrane potential if the potassium ion concentration gradient and resting sodium conductance remain unchanged.

A 63-Year-Old Man Is Dehydrated After 3 Days of Alcohol