Increasing the expression of which membrane protein in a resting neuron would bring RMP closer to threshold voltage?

Question

BlackTom AI · Accepted Answer

Increasing Na+ permeability depolarizes the membrane toward ENa (+60 mV), so adding Na+ leak channels will move RMP closer to threshold.

1) Relevant concepts
- Resting membrane potential (RMP) is set by relative permeabilities (conductances) of ions and their equilibrium potentials (Goldman/weighted average idea). Typical values: RMP ≈ −70 mV, threshold ≈ −55 mV, ENa ≈ +60 mV, EK ≈ −90 mV, ECl ≈ −70 mV. Increasing the permeability (or number) of a specific ion channel shifts Vm toward that ion’s equilibrium potential.

2) Step-by-step reasoning
- At rest the membrane is much more permeable to K+ than to Na+, so Vm is close to EK (negative).
- If Na+ leak channels are increased, the relative contribution of ENa to Vm increases, pulling Vm in the positive direction (depolarization) toward +60 mV.
- Depolarization reduces the gap between RMP (≈ −70 mV) and threshold (≈ −55 mV), so the neuron is closer to firing.

3) Calculations / intermediate steps (illustrative)
Using a simple weighted-average approximation Vm ≈ (gK·EK + gNa·ENa + gCl·ECl)/(gK+gNa+gCl). Pick example conductances: gK = 1, gNa = 0.04, gCl = 0.45.
- Baseline numerator = 1(−90) + 0.04(+60) + 0.45(−70) = −90 + 2.4 −31.5 = −119.1
- Denominator = 1 + 0.04 + 0.45 = 1.49 → Vm ≈ −119.1/1.49 ≈ −79.9 mV
- Double gNa to 0.08: numerator = −90 + 4.8 −31.5 = −116.7; denom = 1.53 → Vm ≈ −76.3 mV
This example shows increasing gNa depolarizes the membrane (less negative), moving it closer to threshold.

4) Why the correct answer is correct
Na+ leak channels increase inward Na+ current at rest, shifting Vm toward ENa and therefore depolarizing the neuron, bringing RMP closer to threshold.

5) Why other options are incorrect (brief)
- Increasing K+ leak channels would hyperpolarize (move Vm toward EK, away from threshold).
- Increasing Cl− conductance usually clamps Vm near ECl (often near or more negative than RMP), not toward threshold.
- Increasing Na+/K+ ATPase activity is electrogenic but tends to make the inside more negative (hyperpolarize) and primarily maintains gradients, not depolarize toward threshold.

6) Conclusion
Therefore the correct choice is a. Na+ leak channels, which matches the provided answer.

Increasing the expression of which membrane protein in a resting neuron would bring RMP closer to threshold voltage?单项选择题

类似问题

A group of neurons expresses a pump which actively transports Vz2- into the cell, and also expresses a limited number of Vz2- leak channels in the cell membrane. How would resting membrane potential change in this scenario compared to a “standard” neuron?

Which of the following statements concerning the neuronal membrane at rest is correct?

The resting potential of a neuron is negative because _____________.

Which ONE of the following factors DOES NOT contribute significantly to the resting membrane potential?

If Na+/K+ ATP-ase were inhibited in a resting neuron, which voltage would the neuron ultimately reach over a long period of time?

Which ONE of the following statements about the resting membrane potential of a neuron is NOT CORRECT?

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