Final answer:
Potassium (K+) has a greater influence on the membrane resting potential because the cell membrane is more permeable to K+ than sodium (Na+), and there are more potassium leakage channels. The sodium-potassium pump heightens this effect by expelling more cations than it takes in, making the inside of the cell negatively charged compared to the outside. Lastly, the behavior of K+ channels during repolarization asserts the dominance of K+ in maintaining the resting potential.
Step-by-step explanation:
Why Potassium Influences Membrane Resting Potential More
The membrane resting potential is primarily determined by the distribution and movement of ions across the neuronal cell membrane. The inside of a resting cell is negatively charged compared to the outside. This is significantly influenced by potassium (K+) ions due to the cell membrane being more permeable to K+ than to sodium (Na+).
While both ions contribute to the resting potential, K+ has more influence because there are more potassium leakage channels than sodium leakage channels. Hence, K+ diffuses out of the cell more readily which increases its effect on the resting potential. Additionally, the sodium-potassium pump, which pumps three Na+ out of the cell and brings two K+ into the cell, further helps maintain the resting potential by creating a net negative charge inside the cell, further reinforcing the dominance of K+ in contributing to the membrane resting potential.
During repolarization, the K+ channels that opened to allow K+ to exit and Na+ channels to inactivate are closed. This transient increase in K+ permeability and the delayed closure of K+ channels following repolarization ensure that K+ continues to have a major role in restoring and maintaining the resting membrane potential.