Final answer:
Action potentials travel from the neuron's cell body to the axon terminals in a unidirectional manner due to the absolute refractory period that prevents depolarization from moving backward and the all-or-none phenomenon of signal propagation.
Step-by-step explanation:
Action potentials are fundamental to neuronal functioning and communication. They travel in one direction, from the neuron's cell body towards the axon terminals, and this directionality is due to several factors at play during the signal transmission. One crucial factor is the absolute refractory period, which occurs when the voltage-gated Na+ channels are inactivated at the peak of an action potential. During this period, depolarization cannot move backward because the previously opened Na+ channels cannot immediately reopen, making them insensitive to subsequent depolarization.
Furthermore, the propagation of an action potential is an all-or-none phenomenon. When an action potential is triggered, it must reach a certain threshold; if it does, the action potential is generated and propagated with full strength down the axon without diminishing. This all-or-none response ensures that the signal is maintained at its original strength until it reaches the axon terminals. After an action potential occurs, the sodium-potassium pump restores the resting potential of the neuron, further ensuring that the action potential cannot travel backward.
Additionally, myelination of axons and the presence of nodes of Ranvier facilitate the rapid and efficient transmission of action potentials along the axon through a process called saltatory conduction. This also contributes to the unidirectional travel of action potentials. The interplay of these physiological mechanisms precisely controls the flow of electrical signals within the neuron, ensuring the correct delivery and processing of information.