Action Potentials

This set of flashcards is designed to help students remember important terms and concepts related to action potentials and the Hodgkin-Huxley model.

Action Potential

A brief electrical impulse that encodes and transmits information over long distances in nervous systems.

Hodgkin/Huxley experiments

Classic experiments that provided insight into the ionic basis of action potentials, utilizing the squid giant axon.

Voltage-Gated Ion Channels

Channels that open or close in response to changes in membrane potential, playing a key role in the generation of action potentials.

Depolarization

The process by which the membrane potential becomes less negative compared to the resting membrane potential.

Resting Membrane Potential (RMP)

The electrical potential difference across the plasma membrane when the cell is at rest.

Sustained Leakage Current

The constant flow of current that compensates for leakage through non-gated ion channels.

Repolarization

The process by which the membrane potential returns to its resting state after depolarization.

Peak Depolarization

The maximum positive spike in membrane potential during an action potential.

Threshold

The membrane potential that must be reached for an action potential to be initiated.

Absolute Refractory Period

The period following an action potential during which a cell cannot initiate another action potential.

Relative Refractory Period

The period following an action potential during which a greater-than-normal stimulus can elicit another action potential.

Passive Properties of Axons

The electrical properties of axons that affect the propagation of action potentials.

Tetrodotoxin (TTX)

A neurotoxin that blocks voltage-gated sodium channels, preventing action potentials.

Tetraethylammonium (TEA)

A compound that blocks potassium channels, used to study ionic currents.

Inactivation

The process by which voltage-gated sodium channels become non-conductive after opening.

Deinactivation

The recovery of voltage-gated sodium channels from inactivation, allowing them to open again.

Conductance

A measure of how easily ions can flow through a channel or membrane, typically represented by g.

Current

The flow of electric charge, typically measured as the movement of ions across a membrane.

Ion Channels

Proteins in the membrane that allow the passage of ions, crucial for generating action potentials.

Equilibrium Potential (E)

The membrane potential at which the net flow of a specific ion across the membrane is zero.

Voltage-Clamp Technique

An experimental procedure used to hold the membrane potential of a cell at a set value to study ionic currents.

Leakage Channels

Ion channels that are always open and contribute to the resting membrane potential.

Capacitative Current

The transient current due to charge displacement in a membrane during changes in voltage.

Control Current

The baseline measurement against which all other currents are compared.

Hyperpolarization

An increase in the membrane potential that makes it more negative than the resting potential.

Positive Feedback Loop

A process where an increase in a particular effect leads to further increases in that effect, critical in action potential generation.

Na+/K+ Pump

A protein that uses ATP to transport sodium out of the cell and potassium into the cell, crucial for maintaining resting potential.

Threshold Values

Specific membrane potentials that determine whether an action potential occurs.

Giant Axon

An enlarged axon that facilitates experimental studies due to its larger size and ease of manipulation.

Impulse Propagation

The movement of an action potential along an axon.

Node of Ranvier

Gaps in the myelin sheath where voltage-gated sodium channels are concentrated.

Saltatory Conduction

The rapid conductance of action potentials along myelinated axons, jumping from node to node.

Voltage Dependence

The relationship between voltage and the opening/closing of ion channels.

Conductance Curve

A graphical representation of how the conductance of ion channels varies with voltage.

Postinhibitory Rebound (PIR)

An excitatory response occurring after the offset of a hyperpolarizing current.

Inhibitory Synaptic Potential

A potential that reduces the likelihood of neuron firing by making it more negative.

Nudibranch Clione

A marine organism used to study the excitatory responses of neurons.

Membrane Theory

Bernstein's proposition that high selective permeability creates a resting membrane potential.

Current-Voltage Plot

A graph depicting the relationship between current and voltage in neuronal membranes.

Inward Current

A current that flows into a cell, often associated with Na+ influx during depolarization.

Outward Current

A current that flows out of a cell, often associated with K+ efflux during repolarization.

Activation Gate

The part of a voltage-gated ion channel that opens when membrane potential reaches threshold.

Inactivation Gate

The part of a voltage-gated ion channel that closes after the channel has opened, preventing further ion flow.

Feedback Circuit

A system that regulates the flow of currents, used in the voltage clamp methodology.

Rheotome

An early device for measuring electrical potentials in biological tissues.

Electrical Impulse

A wave of depolarization that travels along an axon, constituting an action potential.

Charge Neutrality

A condition where the overall charge within a biological system remains balanced; crucial for maintaining function.

Currents through Gated Channels

Ionic flows through channels that open in response to specific stimuli.

Fixed Volume of Current

The amount of current that remains constant regardless of changes in voltage.

Bioelectricity

The electric potential and currents originating from the biological activity of cells.

Pathway Resistance

The resistance encountered in a biological pathway, affecting the flow of ions.

Membrane Capacitance

The ability of a membrane to store charge, influencing action potential dynamics.

Intrinsic Properties

Inherent characteristics of ion channels that dictate their functional outcomes.

Adaptive Response

The process by which neurons adjust their thresholds in response to varying stimuli.

Spike Frequency

The rate at which action potentials are generated by a neuron.

Ion Channel Structure

The physical configuration of ion channels that determines their function.

Conductance Equations

Mathematical representations that describe how ionic current changes with voltage and time.

Passive Current Flow

The movement of ions across membranes in response to existing gradients without active processes.

Interstitial Fluid

The fluid that surrounds neurons and provides ionic balance necessary for action potentials.

Neuronal Threshold Plasticity

The ability of a neuron to alter its threshold in response to experience or stimuli.

Action Potentials in Physiology

The role of action potentials in signaling within and between neurons in the nervous system.

Structural Basis for Inactivation

The physical mechanism within ion channels that causes them to close after opening.

Evolutionary Conservation of Ion Channels

The phenomenon where fundamental aspects of ion channel function are preserved across species.

Mutations in Ion Channel Genes

Genetic alterations that can affect the function of ion channels, impacting neural signaling.

Membrane Potential Dynamics

The changes in electrical charge across a membrane over time, critical to neuronal function.

Voltage Sensor

The component of ion channels that responds to changes in membrane potential.

Equilibrium Data

Information regarding the steady-state conditions of an ion in the system.

Dynamic Changes in Membrane Resistance

Alterations in the ability of a membrane to impede current flow due to functional changes in ion channels.

Hodgkin-Huxley Model

A mathematical model describing how action potentials are initiated and propagated in neurons.