But action potentials move in one direction. This is achieved because the sodium channels have a refractory period following activation, during which they cannot open again. This ensures that the action potential is propagated in a specific direction along the axon.

Why do action potentials only propagate one way?

Propagation of the action potential occurs in one direction only because of the short inactive period of the Na⁺ channels and the brief hyperpolarization resulting from K⁺ efflux (see Figure 21-14). ... In myelinated neurons, voltage-gated Na⁺ channels are concentrated at nodes of Ranvier.

Why neurons are unidirectional?

Because action potentials can only travel from dendrites through to the axon, the transmission must be unidirectional.