Main Answer
On concentrations, the first significantly affected action potential(s) is after one action potential.The option D is correct.
Explanation
An action potential is an electrical signal that travels along a neuron or muscle fiber, transmitting information. When an action potential occurs, it causes a rapid change in the concentration of certain ions, such as sodium (Na+) and potassium (K+), in the vicinity of the neuron or muscle fiber.
The first significant change in ion concentrations occurs during the action potential itself, as sodium ions rush into the cell and potassium ions leave the cell. However, these changes are relatively brief and return to baseline levels soon after the action potential has passed.
It is only after a series of action potentials that more sustained changes in ion concentrations may occur, as a result of processes such as neurotransmitter release and reuptake, ion channel regulation, and metabolic processes.The option D is correct.