Final answer:
The resting period after an action potential when the neuron cannot fire again is called the refractory period. It ensures ion channels return to their resting states and maintains unidirectional flow of impulses.
Step-by-step explanation:
After an action potential, there is a period known as the refractory period where the neuron is "resting" and not able to fire again.
During the action potential, the neuron undergoes a rapid change in electric charge across its membrane, which is then followed by a restoration to the resting state or repolarization. This restoration is achieved by the closing of voltage-gated sodium channels and the continued outflow of potassium ions, which returns the interior of the neuron to a negative charge. The sodium-potassium ATPase plays a crucial role throughout, continuously pumping Na+ out of the neuron and K+ back into the neuron, maintaining the resting potential.
The refractory period is divided into two phases: the absolute refractory period, where a new action potential cannot yet begin, and the relative refractory period, where a new action potential can only begin with a stronger stimulus. This period allows the ion channels to return to their resting states and ensures that each action potential is a discrete, all-or-nothing event, maintaining the unidirectional flow of nerve impulses.