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
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