Figure 44.7 Membranes Can Be Depolarized or Hyperpolarized The resting potential is produced mostly by leak K+ channels with a small contribution from leak Na+ channels (not shown here). A shift from the resting potential to a less negative membrane potential caused by increased Na+ permeability is called depolarization. Hyperpolarization occurs when the membrane potential becomes more negative as when the permeability of the membrane to K+ increases.