Voltage-Gated Sodium Channels (Part 1-3)

These flashcards cover key concepts related to the structure, function, and action potential mechanisms of voltage-gated sodium channels as discussed in the lecture.

What is the main function of voltage-gated sodium channels (NaVs)?

They facilitate the rapid depolarization of the membrane potential during the action potential.

Describe the structure of voltage-gated sodium channels.

They are large, multimeric complexes composed of an alpha subunit and auxiliary beta subunits, with an ion-conducting aqueous pore contained entirely within the alpha subunit.

What are the five phases of the action potential?

1. Resting State, 2. Rising Phase, 3. Overshoot, 4. Falling Phase, 5. Undershoot.

What triggers the inactivation of Na+ channels during an action potential?

Inactivation occurs when the membrane potential approaches sodium's equilibrium potential (ENa) and a part of the channel blocks the open pore.

What role do beta subunits play in sodium channels?

Beta subunits modulate the gating, kinetics, and localization of the alpha subunit, affecting channel function.

What is the role of phosphorylation in NaV channels?

Phosphorylation can either increase or decrease Na+ currents, depending on the type of NaV channel and which protein kinase (PKA or PKC) is involved.

What is the significance of the selectivity filter in NaV channels?

The selectivity filter is negatively charged, allowing sodium ions to pass while excluding potassium ions.

How do toxins affect voltage-gated sodium channels?

Toxins can inhibit sodium channels by blocking the pore or altering the gating mechanism, affecting sodium ion flow.

What is the consequence of gain-of-function mutations in Nav1.7?

They can cause severe pain syndromes such as inherited erythromelalgia.

How does the sliding helix model explain channel activation in NaVs?

Depolarization repels the positively charged S4 region outward, causing conformational changes that open the channel pore.