Which ion is primarily responsible for the resting membrane potential in neurons?

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The question asks: Which ion is primarily responsible for the resting membrane potential in neurons?

In neuronal membranes, the resting membrane potential is mainly governed by the permeability of the membrane to potassium ions (K+) via leak channels. At rest, the membrane is more permeable to K+ than to other ions, so K+ conductance sets the resting potential. The resting potential is typically around -65 to -70 mV in many neurons, a value largely determined by the equilibrium potential of potassium and the membrane’s high permeability to K+.

Even though several ions are present and contribute to the electrical landscape, potassium leaks out of the cell through channels more readily than others, driving the membrane potential toward the potassium equilibrium potential. If the membrane were equally permeable to all ions, or if Na+ conductance dominated, the resting potential would be different, and it would not be near the usual negative value observed.

To understand why other ions are less responsible at rest: sodium ions (Na+) have a larger electrochemical gradient inward, but the membrane is relatively less permeable to Na+ at rest, so Na+ conductance has a smaller influence on the resting potential. Chloride ions (Cl−) contribute to membrane potential in certain contexts, especially with shunting inhibition or extracellular conditions, but they do not establish the resting potential as strongly as K+. Calcium ions (Ca2+) have very low membrane permeability at rest in most neurons, so they do not set the resting potential.

Therefore, selecting potassium (K+) as the primary ion aligns with the dominant role of K+ leak channels in establishing the resting membrane potential. The rest of the ions—Na+, Cl−, and Ca2+—play roles in shaping excitability and signaling but do not predominantly determine the baseline resting potential on a day-to-day basis.

2261 BIOSC 1500 SEC1030 Cell Bio 1500'25 first midterm, 75 min version

Which ion is primarily responsible for the resting membrane potential in neurons?

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