The movement of ions and other atomic or molecular substances across cell membranes without the need for energy input is known as

passive transport

Explanation:

The movement of ions across a cellular membrane without the need for energy input is known as passive transport. Diffusion is the passive movement of molecules from an area of high concentration to low concentration. Voltage describes the difference in electrical potential between two separate points, and isotonic movement describes the activity of a system at equilibrium.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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