Which of the following ions is most likely to cross the plasma membrane of a resting neuron?
A) K+
B) Na+
C) Ca2+
D) Cl−
E) Mg2+

Question

Quizplus · Accepted Answer

Resting neurons have more K+ channels than any other ion channels on their plasma membrane. Thus, K+ ions are more likely to cross the plasma membrane of a resting neuron. This movement is governed by the concentration gradient of K+ ions, which is higher inside the cell than outside. As a result, the K+ ions tend to diffuse out of the cell down their concentration gradient, leading to a net negative charge inside the cell relative to the outside. This difference in charge across the plasma membrane is what gives rise to the resting membrane potential of neurons.

Which of the Following Ions Is Most Likely to Cross