Membrane Potential and Electrical Signals

Vocabulary flashcards covering cellular membrane potential, Nernst and Goldman equations, ion channels, resting potential, and neural signaling.

Membrane Potential

The voltage difference between the inside and the outside of a cell.

Potassium Leak Channels ($K^+$ leak channels)

Channels in the cell membrane that allow potassium ions ($K^+$) to move freely across the membrane down their concentration gradient.

Equilibrium Potential ($E_{ion}$)

The membrane potential point at which electrical forces pulling an ion into the cell balance the concentration gradient forces pushing that ion out of the cell.

Nernst Equation

An equation used to determine the equilibrium potential for any given ion: $E_{ion} = \frac{RT}{zF} \text{ln}\frac{[ion]_{outside}}{[ion]_{inside}}$.

Simplified Nernst Equation (at $37^\text{o}C$)

The simplified formula for equilibrium potential assuming normal human body temperature ($310.15\,K$): $E_{ion} = \frac{61.54\,mV}{z} \text{log}\frac{[ion]_{outside}}{[ion]_{inside}}$.

Goldman Equation

An equation used to calculate membrane potential ($V_m$) by accounting for relative permeabilities and concentration gradients of multiple ions ($K^+$ and $Na^+$): $V_m = 61.54\,mV \times \text{log}\left(\frac{P_{K^+}[K^+]_o + P_{Na^+}[Na^+]_o}{P_{K^+}[K^+]_i + P_{Na^+}[Na^+]_i}\right)$.

Electrogenic Pump ($Na^+/K^+$ ATPase)

A membrane pump that hydrolyzes ATP to move $3\,Na^+$ ions out of the cell and $2\,K^+$ ions inside against their concentration gradients, contributing to a net negative membrane potential.

Resting Membrane Potential

The stable membrane potential of a neuron at rest (typically $-70\,mV$), which is highly sensitive to extracellular $K^+$ concentrations due to high $K^+$ permeability.

Blood-Brain Barrier

A mechanism in the nervous system that isolates the central nervous system (CNS) from fluctuations in blood $K^+$ concentration.

Potassium Spatial Buffering

A process in which astrocytes take up extracellular $K^+$ and redistribute it throughout the extracellular fluid of the central nervous system to prevent local accumulation of $K^+$.

Gated-Ion Channels

Membrane channels with open or closed gates used by neurons to create localized changes in membrane potential to generate electrical signals.

Depolarization

A change in membrane potential to a more positive value, occurring when gated $Na^+$ channels open and $Na^+$ flows in toward $E_{Na^+}$.

Hyperpolarization

A change in membrane potential to a more negative value, occurring when gated $K^+$ channels open and $K^+$ flows out toward $E_{K^+}$.

Repolarization

The process by which the membrane potential ($V_m$) returns back toward the resting membrane potential.

Action Potential (AP)

One of the two main types of electrical signals generated by neurons to convey information.

Post-Synaptic Potential (PSP)

Also known as a graded potential, one of the two main types of electrical signals generated by neurons.