Neurophysiology: Resting Membrane Potential and Ion Dynamics

Vocabulary flashcards defining core terms, values, equations, and physiological mechanisms underlying the resting membrane potential of neurons.

Ion channels

Protein pores that allow selected ions to move passively down their electrochemical gradients without directly requiring ATP.

Ion pumps

Transport proteins that use energy (such as ATP) to move ions against their concentration gradients.

Resting membrane potential

The electrical voltage difference across the membrane (approximately $-75\,\text{mV}$) where combined ionic currents produce no net current.

Potassium equilibrium potential ($E_K$)

The membrane voltage (approximately $-90\,\text{mV}$) at which electrical and concentration forces acting on $K^+$ balance, producing no net movement of $K^+$.

Sodium equilibrium potential ($E_{Na}$)

The membrane voltage (approximately $+60\,\text{mV}$) at which electrical and concentration forces acting on $Na^+$ balance.

Membrane potential

The actual electrical voltage difference between the inside and outside of a cell resulting from all permeable ions.

Equilibrium potential

The specific membrane voltage at which an ion's concentration gradient and electrical gradient balance, causing no net movement of that ion.

Extracellular KCl addition

An alteration that raises extracellular $K^+$, weakens the $K^+$ concentration gradient, makes $E_K$ less negative, and depolarizes the resting neuron.

Extracellular NaCl addition

An alteration that has little immediate effect on resting membrane potential because the resting membrane has low permeability to $Na^+$.

Nernst equation

A mathematical formula used to calculate the equilibrium potential for a single ion based on its charge and its intracellular and extracellular concentrations.

Goldman equation

A mathematical formula used to estimate membrane potential by considering the concentrations and relative membrane permeabilities of multiple ions (commonly $K^+$, $Na^+$, and $Cl^-$).

Current

The rate at which electrical charge moves, carried in neurons by moving ions such as $Na^+$, $K^+$, Ca^{2+}$, and Cl^-$$.

Conventional current

Current direction defined by the movement of positive charge, where positive ions entering a cell produce inward current and positive ions leaving produce outward current.

Leak channels

Ion channels that are usually open at rest, allowing ions to move passively down their electrochemical gradients (such as $K^+$ leak channels).

Semipermeable membrane

A selectively permeable membrane that allows certain substances to cross more easily than others.

Depolarization

A change in membrane potential where the voltage becomes more positive or less negative, such as a shift from $-75\,\text{mV}$ to $-60\,\text{mV}$.

Hyperpolarization

A change in membrane potential where the voltage becomes more negative, such as a shift from $-75\,\text{mV}$ to $-90\,\text{mV}$.

$Na^+/K^+$ pump ($Na^+/K^+$ ATPase)

A membrane protein that uses one ATP molecule to export $3\,Na^+$ and import $2\,K^+$, maintaining required ion gradients.