Resting Membrane Potential
The resting membrane potential is caused by the difference in ionic concentrations and conductances across the membrane of the cell during phase 4 of the action potential. The normal resting membrane potential in the ventricular myocardium is about -85 to -95 mV. This potential is determined by the selective permeability of the cell membrane to various ions. The membrane is most permeable to K+ and relatively impermeable to other ions. The resting membrane potential is therefore dominated by the K+ equilibrium potential according to the K+ gradient across the cell membrane. The membrane potential can be calculated using the Goldman-Hodgkin-Katz voltage equation. The maintenance of this electrical gradient is due to various ion pumps and exchange mechanisms, including the Na+-K+ ion exchange pump, the Na+-Ca2+ exchanger current and the IK1 inwardly rectifying K+ current. I is the symbol for an electric current.
Intracellularly (within the cell), K+ is the principal cation, and phosphate and the conjugate bases of organic acids are the dominant anions. Extracellularly (outside the cell), Na+ and Cl- predominate
Read more about this topic: Cardiac Action Potential
Famous quotes containing the words resting and/or potential:
“We judge a horse not only by its pace on a racecourse, but also by its walk, nay, when resting in its stable.”
—Michel de Montaigne (1533–1592)
“Children are potentially free and their life directly embodies nothing save potential freedom. Consequently they are not things and cannot be the property either of their parents or others.”
—Georg Wilhelm Friedrich Hegel (1770–1831)