Neuronal Membrane Potentials and Ion Movement (Weill Cornell Medicine)

Vocabulary flashcards covering key terms related to neuronal membrane structure, ion movement, diffusion, and electrical properties from the video notes.

Ion

A charged particle; ions exist both outside neurons (extracellular fluid) and inside (cytosol); movement underlies electrical signaling.

Cation

A positively charged ion (more protons than electrons).

Anion

A negatively charged ion (more electrons than protons).

Extracellular fluid

The watery fluid surrounding neurons; contains ions such as Na+ and Cl−.

Cytosol

The intracellular fluid inside neurons; contains ions such as K+.

Neuronal membrane

The cell membrane that is permeable to ions only through ion channels and pumps.

Phospholipid bilayer

Two-layer membrane structure with polar hydrophilic heads and nonpolar hydrophobic tails that forms the neuron’s boundary.

Hydrophilic

Water-loving; polar regions that interact with water.

Hydrophobic

Water-fearing; nonpolar regions that repel water.

Phospholipid head

Polar region containing phosphate; part of the bilayer surface facing water.

Phospholipid tail

Nonpolar fatty acid chains forming the bilayer’s interior.

Saturated fatty acid

Fatty acid with no double bonds; straight chains in the phospholipid tails.

Unsaturated fatty acid

Fatty acid with one or more double bonds; kinked tails in the bilayer.

Ion channel

A protein pore in the membrane that allows selective passage of ions; can be gated.

Ion pump

A membrane protein that uses energy (ATP) to move ions against their concentration gradient.

Gated channel

Ion channel that can open or close in response to stimuli to regulate ion flow.

Resting membrane potential

Voltage across the neuronal membrane when not firing (about −65 mV); inside is more negative than outside.

Equilibrium potential (Eion)

The membrane potential where there is no net movement of a given ion; depends on concentration gradient, charge, temperature.

Potassium equilibrium potential

The equilibrium potential for K+; a major determinant of the resting membrane potential due to higher K+ permeability.

Nernst equation

Equation used to calculate the equilibrium potential for an ion; conceptually considers temperature, ion charge, and concentration ratio.

Diffusion

Random movement of particles from high to low concentration driven by kinetic energy; occurs along a concentration gradient.

Concentration gradient

Unequal concentrations of an ion across the membrane that drives diffusion.

Electrical current

The flow of electric charges across the membrane; measured in amperes (I).

Electrical potential (voltage)

A force acting on a charged particle due to a difference in charge across space; measured in volts or millivolts (V or mV).

Conductance

The ease with which an electrical charge can move; symbol g; unit siemens.

Resistance

Opposition to the flow of current; inverse of conductance; unit ohms.

Ohm’s Law

Relationship I = gV and V = IR between current, conductance, voltage, and resistance.

Sodium-Potassium Pump

Active transporter that moves 3 Na+ out and 2 K+ into the cell using ATP, maintaining ion gradients.

ATP

Adenosine triphosphate; the energy currency used by ion pumps.

Permeability

The property of a membrane that describes how easily ions can cross, largely determined by channels and pumps.

Membrane potential

The electrical potential difference across the membrane; often discussed as resting membrane potential when the neuron is not firing.