How does opening a gated ion channel affect resting membrane potential?

Answer 1

Since the concentration gradient is very large for potassium (where the concentration is much greater ( ~20-30X) inside the cell than outside the cell), reducing this concentration gradient by increasing the concentration of extracellular potassium would result in decreased efflux of potassium through leak channels. This decrease in efflux would result in immediate depolarization of the cell membrane, and would probably be sufficient to generate an action potential (if the depolarization met the threshold level of ~55mV). Now this would only apply to the first generation of an action potential, because if the cell were not able to restore its resting membrane potential (as in the case of increased XC potassium), no subsequent action potentials would be generated. Remember that eventually, equilibrium would be reached between the concentrations of potassium inside and outside the cell, meaning no net flux of those ions, meaning no membrane potential.

Answer 2

The Resting Membrane Potential would become more negative (hyperpolarized).

The neuron's RMP is normally -70mV, which is more positive than potassium's equilibrium constant of -94mV. This is because sodium leaks into the cell (going down its concentration gradient) making it slightly more positive inside the cell, thereby allowing some of the potassium ions to travel down their concentration gradient and out of the cell. This continuous slow leak of these two ions creates the -70mV RMP. These concentrations are then maintained by the sodium/potassium pump.

Now to the point of the question, if the extracellular concentration of sodium decreases, there is less push for sodium to enter the cell (going down a lesser concentration gradient), so the cell's RMP becomes more negative (closer to potassium's equilibrium constant of -94mV) or hyperpolarized and therefore less likely to achieve threshold with normal stimulation.

Answer 3

If the concentration of large intracellular anions..i.e. proteins, which are unable to cross the membrane due to their large size.. were to increase, the resting potential would reach a more negative state, a deviation from -70mV to a more negative value do to these anions.

Answer 4

Assuming your question is referring to when the membrane potential is at equilibrium, when inside the cell is more positive (more K+) and outside is more negative (more Cl-)

• K+ ion channel: K+ rushes out
• NA+ ion channel: some Na+ is leaking in
• Cl- ion channel: Cl- rushes in
• ATP powered pump: pumps K+ and Na+ back in against concentration gradient.

Causing a depolarization. If the depolarization is significant enough to cross threshold it triggers an action potential.

Answer 5

increase