Significance of Ion Channels and Membrane Potential Changes in Cells

Ion channels are integral membrane proteins spanning membranes. These proteins have virtual holes inside (which actually serve as tunnels) allowing ions to pass through, thereby circumventing the hydrophobic barrier of the lipid bilayer that separates cell interior from extracellular space. The cations and anions pass through their specialized channels in a strictly regulated way, in which the diameter and fixed charges in the actual ion tunnel are important, but not exclusive, restricting structural characteristics. Ion channels of cells from the nervous system and muscles are well studied and display enormous diversity (Lewis and Cahalan 1988; Pieri et al. 1989; Jan and Jan 1990).