ABSTRACT
A few cell types are said to be excitable because they are able, when suitably stimulated, to generate rapid, brief, alterations in this voltage that can be actively propagated over the cells' surface, an event termed an action potential. Excitable cells include neurons, skeletal, cardiac and smooth muscle cells, some endocrine cells and the plasma membrane of some oocytes. The transmembrane potential that exists across an excitable cell when in an unstimulated state is called the resting potential. Being able to measure directly resting potentials, action potentials and the other potentials that occur in nerve and muscle cells is crucial for understanding how these cells work and interact. A standard technique for measuring transmembrane potentials in individual cells is intracellular recording. Resting potentials arise because there is a difference in the concentrations of ions between the inside and outside of the cell and because the cell membrane has different permeabilities for these ions.
