lecture tuesday 8/26

Vocabulary flashcards covering key terms from the neurophysiology notes on resting potential, gradients, channels, and basic neuron signaling.

Resting membrane potential

The steady-state electrical difference across the neuron's membrane when at rest, typically about -70 mV (inside negative), established by ion gradients, intracellular anionic proteins, leak channels, and the Na+/K+ pump.

Intracellular fluid (ICF)

Fluid inside the neuron that contains more negative charges (including anionic proteins) and differs in ion concentrations from the outside.

Extracellular fluid (ECF)

Fluid outside the neuron that has higher concentrations of certain cations (e.g., Na+, Ca2+) and contributes to the positive external environment.

Anionic proteins

Negatively charged intracellular proteins that remain inside the cell and contribute to a more negative internal environment.

Sodium-potassium pump (Na+/K+-ATPase)

A membrane transporter that pumps 3 Na+ out and 2 K+ in per ATP, helping maintain ion gradients and resting membrane potential.

Potassium leak channels

Potassium-selective channels that are open at rest, allowing K+ to leak out and contribute to a negative interior.

Sodium leak channels

Sodium-permeable channels present in lower numbers that allow some Na+ to leak into the cell, opposing the resting negativity.

Calcium gradient

Calcium (Ca2+) is higher outside the cell; opening Ca2+ channels allows Ca2+ to flow where gradients favor.

Chemical gradient

The uneven distribution of ions across the membrane (concentration gradient) that drives diffusion when channels are permeable.

Electrical gradient

The difference in electrical charge across the membrane (inside negative, outside positive) influencing ion movement.

Equilibrium potential (Nernst potential)

The membrane potential at which a particular ion would have no net flow, balancing its chemical and electrical gradients.

Potassium equilibrium potential (E_K)

The membrane potential at which K+ diffusion down its gradient is balanced by electrical forces (roughly -90 mV for K+).

Sodium equilibrium potential (E_Na)

The membrane potential at which Na+ diffusion is balanced by electrical forces (roughly +60 mV for Na+).

Depolarization

A shift in membrane potential toward less negative or more positive values, typically by opening Na+ channels and allowing inward Na+ flow.

Hyperpolarization

A shift toward more negative membrane potential, often due to K+ efflux or other mechanisms that increase negativity inside.

Permeability

The ease with which the membrane allows ions to pass, determined by the number and state of open channels.

Graded potential

A small, local change in membrane potential that can vary in size and can summate; occurs in dendrites and soma.

Voltage-gated ion channels

Ion channels that open or close in response to changes in membrane potential, enabling rapid signaling (e.g., action potentials).

Ligand-gated (chemical) channels

Ion channels that open in response to a chemical signal (neurotransmitter binding), mediating chemical stimuli.

Mechanically gated channels

Ion channels opened by physical deformation of the membrane (e.g., touch receptors bending of the membrane).

Action potential

The rapid, all-or-none electrical signal fired by a neuron when the membrane reaches threshold, driven by Na+ influx followed by K+ efflux.

Goldman-Hodgkin-Katz equation

A comprehensive equation that accounts for multiple ions and their permeabilities to estimate the resting membrane potential.

Nernst equation

An equation used to calculate the equilibrium potential for a single ion based on its concentration gradient.

Electrochemical gradient

The combined influence of chemical and electrical gradients on the movement of ions across the membrane.