What is Nernst's equation?
Nernst equation determines the resting potential of cell membranes in the body as a factor of ion concentration inside and outside the cell. The cells are the basic unit of the body and the environment inside the cell is separated from the outside by the cell membrane. The intracellular environment contains a concentration of ions that differ from the concentration of the extracellular environment, so that an electric charge develops and is referred to as resting potential. The ions that have the most influential in determining the resting potential are also those to which the cell membrane is most permeable: sodium and potassium. Inside the cell there is a higher potassium concentration than outside the cell and the opposite applies to sodium ion.
For many cells in the body, resting potential remains constant throughout the duration of cellular life. However, in exciting cells such as nerve and muscle cells, resting potential simply refers to membrane potential when the cell is not excited. Excitable cell is a cell that generates an electrical impulse that causes the cell to become a SVALunar cells or fires a signal in the case of a nerve cell.
excitation results in a change in the permeability of the membrane to the ions, especially potassium and sodium. This allows the flow of ions from the area of higher concentration into the area of lower concentration, and this flow causes an electric current that changes the charge over the membrane. In this case, therefore, the Nernst equation does not apply, because the Nernst equation takes into account only the concentration of ions if there is no permeability in the cell membrane.
The factors of the Nernst equation in constants such as the Faraday Constant, the universal gas constant, the absolute body temperature and the valence of the ions considered. Potassium is the most commonly considered ion in the equation. It is the ion of the greatest throughput, so it flows through the membrane most.
Nernst's equation was criticized because it assumes that there is no clear flow of ions through the cell membrane. There is never a realistic or100 ion flow, because ions escape due to leakage or are actively pumped by a cell over the membrane. In many cases, the more universal Goldman equation is preferred to predict the membrane potential. The Goldman equation takes into account the permeability of the membrane to the ions for a more accurate assessment of the membrane potential and can be used for exciting and non -expansive cells.