Membrane Electrophysiology – Resting Membrane Potential

Vocabulary flashcards covering key terms from Dr. Reynolds’ lecture on the biophysical basis of the resting membrane potential.

Resting Membrane Potential (RMP)

The steady difference in electric potential between the inside and outside of an excitable cell at rest; about –70 mV in a motor neuron.

Equilibrium Potential (Eₓ)

The membrane voltage at which the net flux of a specific ion is zero because its electrical and concentration gradients are balanced.

Nernst Equation

Formula that calculates an ion’s equilibrium potential from its intra- and extracellular concentrations and valence.

Sodium–Potassium Pump (Na⁺/K⁺-ATPase)

Primary-active transporter that exports 3 Na⁺ and imports 2 K⁺ per ATP, establishing Na⁺/K⁺ gradients and contributing to RMP.

Concentration Gradient

Difference in the chemical concentration of an ion across a membrane that drives diffusion from high to low concentration.

Electrical Gradient

Difference in electrical charge across a membrane that attracts opposite charges and repels like charges.

Electrochemical Gradient

Combined influence of an ion’s concentration and electrical gradients that dictates its net movement.

Leak Channel

Ion channel that remains open at rest, allowing passive ion flow; key example is the K⁺ leak channel.

Membrane Permeability

The ease with which ions cross the membrane, determined by number and state of ion channels.

Potassium Leak Channel

Non-gated K⁺ channel whose constant activity makes K⁺ the dominant determinant of RMP.

Action Potential (AP)

Rapid, transient reversal of membrane potential that propagates along excitable cells; cannot occur without an established RMP.

Depolarization

Change in membrane potential toward 0 mV or positive values relative to RMP.

Repolarization

Return of membrane potential back toward the resting negative value after depolarization.

Hyperpolarization

Membrane potential becoming more negative than the resting level.

Hyperkalemia

Elevated extracellular K⁺ that decreases the K⁺ gradient and makes the RMP less negative (cells more excitable).

Hypokalemia

Reduced extracellular K⁺ that increases the K⁺ gradient and makes the RMP more negative (cells less excitable).

Hypernatremia

Excess extracellular Na⁺ that increases the Na⁺ driving force and can slightly influence RMP.

Hypercalcemia

Elevated extracellular Ca²⁺ that can alter excitability by affecting voltage-gated channels and RMP.

Hyperchloremia

Elevated extracellular Cl⁻ that can influence RMP when Cl⁻ leak channels are present.

Net Driving Force

Difference between membrane potential and an ion’s equilibrium potential multiplied by permeability; determines ion flux rate and direction.

Chemical vs Electrical Steady State

Condition where active pumps maintain concentration gradients while electrical forces balance passive diffusion, producing a stable RMP.

Motor Neuron RMP

Typical resting membrane potential of a motor neuron (≈–70 mV), close to Eₖ because of high K⁺ permeability.