resting membrane potential is an electric potential (reserves), which is formed between the outer surface of the cell membrane and the inner side of the plasma membrane.The inner side of the membrane with respect to the outer surface always has a negative charge.For each type of cell resting potential is practically constant value.Thus, in warm-blooded in skeletal muscle fibers, it is 90 mV for myocardial cells - 80, nerve cells - 60-70.The membrane potential is present in all living cells.
According to modern theories consider the electric supply is generated as a result of the active and passive movement of ions.
passive movement occurs along the concentration gradient, it does not require energy.Membrane cells at rest has a greater permeability to potassium ions.In the cytoplasm of nerve and muscle cells they (potassium ions) present in the thirty to fifty times greater than in the extracellular fluid.Ions in the cytoplasm are located in the free form and diffused according to a concentration gradient, into the extracellular fluid across the membrane.The interstitial fluid intracellular anions are retained on the outer surface of the membrane.
the intracellular space are contained in basic anions pyruvic, acetic, aspartic acid and other organic acids.The inorganic acid is contained in a relatively small amount.Anions permeate through the membrane can not.They remain in the cell.Anions are arranged on the inner side of the membrane.
Due to the fact that the negative charge of the anions and cations in - positive, the outer surface of the membrane has a positive charge, and the internal - negative.
In the extracellular fluid of sodium ions in the eight to ten times greater than in the cell.Their permeability is negligible.However, due to the penetration of sodium ions somewhat reduced membrane potential.When this occurs the diffusion of chloride ions into the cell.The content of these ions in fifteen to thirty times higher than in the extracellular fluids.Due to their penetration of the membrane potential increases slightly.Moreover, in the membrane and there is a particular molecular mechanism.It provides active promotion of potassium and sodium ions in the direction of increased concentration.Thus it supported ionic asymmetry.
active movement of ions is the result of the operation of the sodium-potassium "pump" (pump).The active movement of the cell of sodium ions into the cell due to the penetration of potassium ions.In the dual pump trucks carried carriers, which in turn is carried by the metabolic energy from the decay of ATP.Thanks to the energy of hydrolysis of ATP molecules 2 potassium ions penetrate into the cell, and three sodium ions are transported out.
dormant muscle fibers for the operation of ion pumps spent up to twenty percent of cellular energy.
Under the influence of the enzyme ATPase cleavage of ATP.Poisoning by nerve fibers cyanide monoyodatsetatom, dinitrophenol, and other substances, including stops the process of glycolysis and ATP synthesis, provokes him (ATP) reduction in the cytoplasm and the termination of operation of "pump".The membrane is permeable
also to chlorine ions (in particular muscle fibers).In cells with high permeability, potassium ions and chlorine equally form a membrane at rest.In the other cells of the contribution of the latter in this process is insignificant.
