Modeling repetitive firing and bursting in a small unmyelinated nerve fiber.
The Hodgkin-Huxley equations, originally developed to describe the electrical events in the squid giant axon, have been modified to simulate the ionic and electrical events in a small unmyelinated nerve fiber. The modified equations incorporate an electrogenic sodium-potassium pump, finite intra-axonal volume, a periaxonal space, a calcium current, and calcium-dependent potassium conductance (GKCa). The model shows that adaptation can occur in two ways: increased Na-K pump activity because of periaxonal K accumulation or intra-axonal Na accumulation; or from an increase in (GKCa) caused by calcium accumulating within the axon. Bursting is an extension of adaptation and occurs when the sensitivity of the Na-K pump or (GKCa) to changes in ionic concentration is increased.
D000818:Animals; D001369:Axons / Q000502:physiology*; D001693:Biological Transport, Active; D002118:Calcium / Q000494:pharmacology; D049832:Decapodiformes; D008433:Mathematics; D008564:Membrane Potentials; D008954:Models, Biological; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D012964:Sodium; D011188:Potassium; D002118:Calcium