Question

Action potentials are propagated in a one-way direction down a neuronal plasma membrane because

A) The action potential is of insufficient intensity to stimulate the voltage-gated ion channels behind it
B) The adjacent channels upstream from the action potential are ligand-gated
C) The adjacent channels upstream from the action potential are in a refractory period
D) Voltage-gated ion channels are suppressed
E) The adjacent channels upstream from the action potential are at their threshold potential

Answer 1

Action potentials are propagated in a one-way direction down a neuronal plasma membrane because voltage-gated sodium channels become temporarily inactivated during the peak of depolarization, creating an absolute refractory period.

Step-by-step explanation:

The propagation of action potentials down a neuronal plasma membrane occurs in a one-way direction because voltage-gated Na+ channels become temporarily inactivated during the peak of depolarization, resulting in an absolute refractory period. This prevents the depolarization from spreading back towards previously opened channels.

Therefore, the action potential must propagate towards the axon terminals, providing a one-way direction of transmission. Once the membrane potential returns to the resting state, the voltage-gated Na+ channels reset and can be opened again.