Question

Explain how resting potential is maintained along an axon, the events that lead to an action potential, and the events of an action potential itself.

Answer 1

The resting membrane potential because of small build up of negative ions in the axoplasm along the inside of the membrane and the equal build up of positive ions in the extracellular fluid along the outer surface of the membrane.A typical value of resting membrane potential is -70mV.At resting phase,the axolemma is polarized.The membrane potential changes from its resting value when the membranes permeability to particular ions changes.

The events that takes place during action potential are

a) Depolaristion; when a nerve fiver is stimulated ,the plasma membrane is permeable first permeable to Na+ ions this results in inner side of the axon less negative potential.An action-potential occurs in the memvray of the axon of a neuron when the depolarization reaches certain level called threshold potential (-55mv).The particular which is able to bring the membrane potential to threshold called threshold potential.

b)Repolarization; the next phase is Repolarization : During this phase the influx of Na+ into the axoplasm from ECF is checked and efflux of k+ ions occurs,which leads to returning of axoplasm to the resting State(exit of potassium ions causes a reversal of membrane potential to negative value inside ).This is called Repolarization.

c) Hyperpolarisartion : During this phase the Repolarization typically goes more negative than the resting membrane potential to about -90 mV.This is called hyperpolarisartion.This occurs because of increased k+ permeability that exits while Voltage gated k+ channels are opened.