Final Answer:
Na+ and K+ ions move when a neuron is resting (a) up the membrane channel to the same sides of the membrane
Step-by-step explanation:
During the resting state of a neuron, Na+ and K+ ions exhibit a concentration gradient-driven movement. The sodium-potassium pump actively transports three sodium ions (Na+) out of the neuron for every two potassium ions (K+) it brings in, maintaining a higher concentration of Na+ outside and K+ inside the cell. This establishes an electrochemical gradient. (a)However, at resting membrane potential, the movement of these ions is primarily passive.
The resting membrane potential is approximately -70 millivolts (mV) inside the neuron concerning the extracellular fluid. Both Na+ and K+ channels are selective to their respective ions and are usually closed at rest. However, some leakage channels allow a small flow of these ions. Na+ tends to move down its concentration gradient into the cell, but the membrane potential and closed channels limit its movement. Similarly, K+ tends to move out of the cell due to both its concentration gradient and the negative membrane potential, but again, the closed channels hinder its flow.
This delicate balance results in a net movement of Na+ up its concentration gradient and K+ up its concentration gradient but to the same sides of the membrane, maintaining the resting membrane potential. Understanding these ion movements during the resting state is fundamental to grasping the mechanisms involved in generating and maintaining the neuron's resting membrane potential.