An increase in extracellular potassium ion from 4.0 to 6.0 mEq/L would
A) hyperpolarize the resting membrane potential.
B) make it more difficult to reach threshold and produce an action potential.
C) hypopolarize the resting membrane potential.
D) alter the threshold potential.

Question

Quizplus · Accepted Answer

An increase in extracellular potassium hypopolarizes the cell (makes it less negative)because more K⁺ ions stay inside the cell owing to the reduced concentration gradient.Hyperpolarization of the resting membrane potential (makes it more negative)is caused by a decrease in extracellular potassium.Hyperpolarization resulting from a decrease in extracellular potassium makes it more difficult to reach threshold and produce an action potential.The threshold for action potential does not change with a change in extracellular potassium.

An Increase in Extracellular Potassium Ion from 4