Electrophysiology Quiz: Membrane Potential

The electrical difference between the inside and outside of a cell membrane.

A state where the electrical and chemical forces acting on an ion across the membrane are balanced, preventing net movement of that ion.

The membrane potential of a cell when it is at rest, typically negative.

The ability of a cell membrane to allow certain ions to pass through while restricting others.

The force that drives an ion across the membrane, influenced by both the concentration gradient and the electrical potential.

A small, localized change in membrane potential that decays over distance and time.

A rapid, large change in membrane potential that travels along the axon without decreasing in amplitude.

A technique used to study the electrical properties of cells by inserting a fine electrode into the cell's interior.

A type of ion channel that opens or closes in response to the binding of a specific chemical messenger called a ligand.

A type of ion channel that opens or closes in response to changes in the electrical potential across the membrane.

A type of ion channel that opens or closes in response to mechanical forces, such as stretching or pressure.

A specialized protein embedded in the cell membrane that allows the passage of specific ions across the membrane. They are crucial for maintaining the electrical gradient and generating electrical signals in cells.

The process by which the membrane potential of a neuron changes in response to a stimulus, leading to the generation of an action potential.

The flow of charged particles, specifically ions, across a cell membrane. It is the basis of electrical signaling in cells.

A layer of lipids that forms a barrier between the inside and outside of a cell. It prevents the free movement of ions and other molecules across the membrane.

Proteins that actively transport ions across the cell membrane against their concentration gradients, using energy from ATP. They help establish and maintain the ion gradients necessary for cell function.

The potential difference across a membrane when an ion is in electrochemical equilibrium.

Describes the relative permeability of different ions across the membrane.

This equation describes the relationship between membrane potential, equilibrium potentials, and permeabilities of different ions. It's similar to a weighted average: higher permeability = higher contribution.

Represents the resistance to electrical current flow across the membrane.

Represents the resistance to electrical current flow along the inside of the axon.

Represents the resistance to electrical current flow through the external medium surrounding the axon.

The force that drives the movement of ions across the cell membrane. Depends on both the concentration gradient and the electrical potential.

The permeability of the membrane to a specific ion, determined by the number and type of ion channels present.

The membrane potential at which the driving force for an ion is zero, meaning no net movement of that ion across the membrane.

A change in membrane potential that makes the inside of the cell more negative. Decreases the driving force for potassium (K+) efflux.

A change in membrane potential that makes the inside of the cell more positive, closer to the equilibrium potential for sodium (Na+). Increases the driving force for sodium influx.

The change in membrane potential that occurs in response to a stimulus. Can be graded or all-or-none.

The spread of electrical signals passively along the membrane, without the involvement of voltage-gated ion channels.

Oocytes are unfertilized eggs that can be used to study ion channels. Oocytes normally do not have their own ion channels, so researchers can inject mRNA encoding for specific ion channels into them. These injected channels will be expressed, trafficked to the cell membrane, and become functional. This allows researchers to study the function of these channels using the patch clamp technique.

Oocytes are used to study the effects of mutations on ion channels by comparing the activity of normal channels with those that have mutations known to cause diseases (channelopathies) in humans. The mutations can directly affect the channel's structure, function, or regulation.

When a cell membrane is depolarized, the voltage across the membrane becomes more positive. Na+ channels open when the membrane depolarizes, allowing Na+ ions to flow into the cell. This influx of positive charge further depolarizes the membrane, creating a positive feedback loop.

After being open, Na+ channels quickly inactivate. Inactivation occurs due to a conformational change in the channel protein, preventing further inflow of Na+ ions even though the membrane is still depolarized. This inactivation helps to terminate the action potential.

K+ channels open when the membrane repolarizes (becomes more negative) after depolarization. This allows K+ ions to flow out of the cell, contributing to the repolarization process and restoring the membrane potential to its resting state.

Na+ channels are voltage-gated channels, meaning they open and close in response to changes in the membrane potential. They initiate the action potential by allowing rapid influx of Na+ ions when the membrane depolarizes. This depolarization then triggers the opening of voltage-gated K+ channels, causing repolarization.

Channelopathies are diseases caused by mutations in ion channel genes. These mutations can affect the channel's structure, function, or regulation, leading to a wide range of symptoms, depending on the specific channel affected.

Expression systems, such as oocytes, allow scientists to study channelopathies by comparing the activity of mutated channels to normal channels. This allows researchers to understand how specific mutations affect channel function and to develop potential therapeutic strategies for these diseases.