NBL Module 7 Video Lecture 2

Voltage Gated Channel

A type of ion channel selective for specific ions that opens in response to a depolarization of the membrane potential.

Voltage Gated Sodium Channels

Channels closed at resting membrane potential, open upon depolarization, allowing sodium influx and producing depolarization.

Threshold

Specific membrane potential (-55mV) at which voltage gated sodium channels are activated, crucial for initiating action potentials.

Inward Current

Flow of positive ions into the neuron, producing a negative current, seen when voltage gated sodium channels open.

Inactivation

Closure of voltage gated sodium channels after opening, leading to a transient inward current.

Initial Segment

Region where voltage gated sodium channels are localized, crucial for threshold and action potential initiation.

Positive Feedback Loop

Depolarization leading to opening of more voltage gated sodium channels, enhancing sodium influx and depolarization.

Voltage Sensor

Region within voltage gated sodium channels detecting membrane potential changes, leading to channel activation.

Conformational Change

Movement within the protein due to voltage sensor activation, leading to channel opening and ion movement.

Beta Subunits

Auxiliary subunits of voltage gated sodium channels involved in localizing the channels to specific regions within the axon, like the nodes of Ranvier.

Voltage Gated Sodium Channel

A type of ion channel that opens and allows sodium ions to flow through the cell membrane in response to changes in membrane potential.

Closed State

The state of the voltage gated sodium channel where the channel is not allowing the passage of sodium ions due to conformational changes.

Open State

The state of the voltage gated sodium channel where the channel allows the passage of sodium ions through the pore region.

Inactivated State

The state of the voltage gated sodium channel where the channel is closed and blocked from allowing sodium ions to move across the membrane.

Tetrodotoxin

A naturally occurring toxin that blocks voltage gated sodium channels, preventing the flow of sodium ions.

Local Anesthetics

Compounds like lidocaine and novocaine that inhibit voltage gated sodium channels, used to block pain sensation in dental procedures.

Voltage Gated Potassium Channel

Ion channels that open in response to depolarization, allowing potassium ions to flow out of the cell and repolarize the membrane potential.

Repolarization

The process of restoring the membrane potential back to its resting state after depolarization, often involving the efflux of potassium ions.

Voltage Gated Potassium Channels

Channels that do not have an inactivation gate region and are slower to open compared to voltage gated sodium channels.

Delayed Rectifier Potassium Channels

A major category of voltage gated potassium channels that open more slowly than voltage gated sodium channels and help bring the membrane potential back to the resting state.

Driving Force

The force that drives ion movement, calculated as the difference between the membrane potential and the equilibrium potential for a specific ion.

Refractory Period

A period after an action potential where the neuron is less responsive to further stimulation, divided into absolute and relative refractory periods.

Absolute Refractory Period

A brief period after an action potential where the neuron is unable to generate another action potential regardless of the stimulus strength due to inactivated voltage gated channels.

Relative Refractory Period

The period following the absolute refractory period during which a stronger stimulus is required to generate another action potential as the membrane potential is being repolarized by potassium channels.

Action Potential

The rapid change in membrane potential due to the opening and closing of voltage gated sodium and potassium channels, leading to the propagation of electrical signals in neurons and muscle cells.