Question

Describe how the structural features of the voltage-gated sodium channel are used to generate and propagate action potentials.

Answer 1

First you have to know what an action potential is.
The action potential is an electrochemical process triggered by an electrical impulse that reaches the cell, because of this different specific channels for ions open and close so that the concentration of ions changes. This difference in ion concentrations generates that electochemical gradient.

Once the cell depolarizes (because of the action potential) it tends to repolarize ((through the sodium-potassium pump and other energy-dependent channels). For the case of the voltage-dependent sodium channel, its structure allows it to be a fast channel, which modifies the curve that is generated for the action potential.

Some specifications of voltage-dependent sodium channels

1.- Sodium channels mediate fast depolarization and conduct electrical impulses throughout nerve cells, muscle cells and heart cells.

2.- Sodium channels have a modular architecture, with distinct regions for the pore (is the channel itself through which the ion passes) and the gates (are the structures that allow the entrance of the ion).

3.- At a molecular level, sodium channels are not static: they move extensively in the course of gating and ion translocation.

4.- Sodium channels bind local anaesthetics and various toxins.

Na+ channels consist of various subunits, but only the principal (?) subunit is required for function. The alpha sub-unit consists of four internally homologous domains (labelled I, II, III and IV) they have transmembrane segments. Auxiliary (? subunits [?1 and ?2]?) subunits are important modulators of Na+ channel function.