Resting Membrane Potential and Ionic Equilibrium

Vocabulary flashcards reviewing chemical concepts, electrochemical equilibrium, ion channels, Nernst and Goldman equations, and resting membrane potential.

Ion

A particle with an electrical charge, such as $K^+$ (potassium), $Na^+$ (sodium), or $Cl^-$ (chloride).

Concentration Bracket Notation $[\quad]$

A symbol notation denoting the 'concentration of' a specified substance or ion.

Diffusion

The energy-free movement of a substance from an area of high concentration to an area of low concentration.

Voltage ($V$)

An electrical potential difference created by a difference in charge between two points or across a membrane.

Potassium Ion ($K^+$)

The predominant positively charged ion found inside a resting neuron that can freely enter and exit the cell through selective leak channels.

Sodium Ion ($Na^+$)

A positively charged ion maintained at a higher concentration outside the cell than inside during resting conditions.

Chloride Ion ($Cl^-$)

A negatively charged ion maintained at a higher concentration outside the cell than inside during resting conditions.

Electrochemical Equilibrium

The state established when the force of chemical diffusion driven by a concentration gradient is balanced by the electrical potential force driven by charge differences.

Nernst Equation

An equation given by $E_x = 58 \log \left(\frac{[X]_2}{[X]_1}\right)$ that predicts a $58\,mV$ change in equilibrium potential for every tenfold change in the concentration gradient of a single permeable ion.

10-Fold $K^+$ Gradient Change

A tenfold change in the potassium ion ($K^+$) gradient that produces a linear change of $58\,mV$ in membrane potential.

Hodgkin and Katz (1949)

Researchers who measured a resting membrane potential of $-65\,mV$ in squid giant axons and demonstrated its dependence on external $K^+$ concentration.

Ion Channels

Proteins embedded in the cell membrane that selectively allow specific ions to pass into or out of the cell.

$K^+$ Leak Channel

A membrane channel through which potassium ions ($K^+$) can freely enter and exit the resting neuron along their concentration gradient.

Goldman Equation

An equation given by $V = 58 \log \left(\frac{P_K [K]_2 + P_{Na} [Na]_2 + P_{Cl} [Cl]_1}{P_K [K]_1 + P_{Na} [Na]_1 + P_{Cl} [Cl]_2}\right)$ that calculates membrane potential by considering concentration gradients and membrane permeabilities ($P$) of $K^+$, $Na^+$, and $Cl^-$.

Resting Membrane Potential

The stable electrical potential difference across the cell membrane of a resting neuron (measured at $-65\,mV$ in squid axon), driven primarily by selective $K^+$ permeability and ionic concentration gradients.

Hyperpolarization

A change in membrane potential that makes the inside of the cell more negative relative to the outside, which does not trigger an action potential.