Membrane Potentials and Action Potentials

Flashcards covering key vocabulary related to membrane potentials, graded potentials, and action potentials from the lecture.

Membrane Potential

The electrical potential difference across the cell membrane, maintained by ion movements and pumps like the sodium-potassium pump.

Leakage Channels

Protein tubes embedded in the cell membrane that allow ions, such as potassium, to move down their concentration gradient, influencing the cell's potential.

Graded Potential

A local change in membrane potential resulting from a stimulus, which can be depolarizing or hyperpolarizing, and is summable.

Depolarizing (Exciting)

A change in membrane potential where it becomes less negative, moving from resting potential towards zero, or even positive values, making the cell more excitable.

Hyperpolarizing (Inhibited)

A change in membrane potential where it becomes more negative than the resting potential, making the cell more inhibited.

Sodium-Potassium Pump

An active transport mechanism that helps restore and maintain the resting membrane potential by pumping sodium ions out and potassium ions into the cell.

Action Potential

A rapid, non-decremental, and unidirectional electrical signal generated by the rapid opening and closing of voltage-gated ion channels, leading to a quick depolarization and repolarization of the cell membrane.

Voltage-Gated Channels

Ion channels that open or close in response to changes in the membrane's electrical potential, crucial for generating action potentials.

Threshold

The critical membrane potential (e.g., -55mV) that, when reached, triggers the rapid opening of voltage-gated sodium channels and initiates an action potential.

Inactivation Gate

A specific gate within voltage-gated channels, particularly sodium channels, that closes after depolarization and prevents the channel from reopening until the membrane potential returns to near resting levels, ensuring unidirectional propagation of action potentials.

Unidirectional (Action Potential Propagation)

The characteristic of an action potential to travel in only one direction along a neuron, prevented from moving backward by the inactivation of voltage-gated channels in the previously depolarized region.

Non-decremental (Action Potential)

The property of action potentials that indicates they do not diminish in strength over distance or time, ensuring a consistent signal reaches its target.

Multiple Sclerosis (MS)

A neurological disorder characterized by the disruption of action potential transmission in motor neurons, leading to impaired coordinated movement.

Ligand-Gated Channels (Chemically Gated Channels)

Ion channels that open or close when a specific chemical signal (ligand) binds to them, often involved in generating graded potentials.

Summable (Graded Potentials)

The characteristic of graded potentials where their effects can be added together; increasing the stimulus (e.g., ligand concentration) results in a larger depolarization or hyperpolarization.