Figure 44.9 Action Potentials Travel along Axons (A) There is no loss of signal as an action potential travels along an axon. (B) When an action potential is stimulated in one region of membrane, ionic current flows to and depolarizes adjacent areas of membrane. (C) The advancing wave of depolarization causes more Na⁺ channels to open, and the action potential is generated anew in the next section of membrane. Meanwhile, in the region where the action potential has just fired, the Na⁺ channels are inactivated and the voltage-gated K⁺ channels are still open, rendering this section of the axon incapable of generating an action potential. Hence the action potential cannot “back up,” but moves continuously forward, regenerating itself as it goes.