Resting Membrane Potential in a Neurone

Comprehensive vocabulary flashcards covering the resting membrane potential, ion channels, bioelectrical forces, Gibbs-Donnan equilibrium, and electrochemical equations.

Ions

Charged particles found within solutions in the extracellular and intracellular fluid compartments.

Anions

Negatively charged particles or ions, such as chloride ($\text{Cl}^-$) and intracellular proteins.

Cations

Positively charged particles or ions, such as sodium ($\text{Na}^+$) and potassium ($\text{K}^+$).

Volt

A unit measuring the electrical charge difference between two points in space, where one millivolt ($\text{mV}$) equals $\frac{1}{1000}\,\text{V}$.

Diffusion

The passive movement of solute particles or ions through a semipermeable membrane down their concentration gradient.

Osmosis

The movement of a solvent (water) across a membrane from a region of higher water concentration to a region of lower water concentration.

Leakage Channels

Nongated protein channels that remain open continuously; nerve cells possess substantially more $\text{K}^+$ than $\text{Na}^+$ leakage channels, making resting membrane permeability to $\text{K}^+$ much higher and producing a resting membrane potential of $-70\,\text{mV}$.

Ligand-Gated Channels

Membrane channel receptors that open or close upon the binding of a specific signaling chemical molecule (ligand), thereby mediating neuron excitability.

Voltage-Gated Channels

Ion channels that open or close in response to direct alterations in the membrane potential, typically closed at resting potential and opening via conformational changes during membrane depolarization.

Mechanically Gated Ion Channels

Stress-activated ion channels that open in response to mechanical vibration or pressure, such as those in auditory hair cells opened when sound vibrations tilt stereocilia and stretch linking filaments.

Resting Membrane Potential (RMP)

The stable electrical potential difference measured across the cell membrane of an unstimulated cell, characterized by a negative interior relative to the exterior, typically ranging from $-20\,\text{mV}$ to $-200\,\text{mV}$ across cell types.

Excitable Tissues

Nerve and muscle tissues capable of receiving stimuli (electrical, chemical, mechanical, or thermal) and responding by rapidly altering their resting membrane potentials to generate electrochemical impulses (action potentials).

Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+\text{ ATPase}$)

An electrogenic active transport mechanism spanning the plasma membrane that hydrolyzes $\text{ATP}$ to extrude $3\,\text{Na}^+$ ions from the cell in exchange for bringing $2\,\text{K}^+$ ions inside.

Gibbs-Donnan Equilibrium

The electrochemical equilibrium established across a semipermeable membrane separating two ionic solutions when one compartment contains non-diffusible ions (such as intracellular proteins), causing electrical and chemical energies across the membrane to become equal and opposite.

Donnan Effect

The phenomenon wherein the presence of an impermeant charged species on one side of a membrane causes an asymmetric, predictable redistribution of permeant ions, accumulating oppositely charged diffusible ions on the side of the impermeant species and leading to an osmotic imbalance.

Chemical Driving Force

The thermodynamic force pushing an ion species across a membrane that depends solely upon its concentration gradient between the intracellular and extracellular fluids.

Electrical Driving Force

The electrostatic force pushing an ion species across a membrane that depends on the net electrical potential difference across the lipid bilayer.

Equilibrium Potential

The precise electrical potential difference across the plasma membrane that exactly balances the chemical concentration gradient for a specific permeant ion species, resulting in zero net flux.

Nernst Equation

A mathematical relationship used to calculate the equilibrium potential ($E_{\text{ion}}$) for a given ion based on its concentration ratio across the membrane: $E_{\text{ion}} = \frac{RT}{zF} \ln\left(\frac{[\text{ion}]_o}{[\text{ion}]_i}\right)$ or $E_{\text{ion}} = \left(\frac{60}{z}\right) \log\left(\frac{[\text{ion}]_{\text{out}}}{[\text{ion}]_{\text{in}}}\right)$.

Goldman-Hodgkin-Katz (GHK) Equation

A constant-field equation that calculates the aggregate membrane potential ($V_m$) by factoring in the concentration gradients as well as relative membrane permeabilities ($P_{\text{K}}$, $P_{\text{Na}}$, $P_{\text{Cl}}$) of sodium, potassium, and chloride ions.