The action potential (AP) represents the transient change of the potential difference between the outer and inner surfaces of the membrane (or tissue between two points), to about Thoroe arises at the time of excitation. When registering neuronal action potential by means of microelectrode those observed typical pico used different potential. In simplified form, when an AP can vyd e casting the following phases: initial phase of the depolarization, then rapidly reducing the e of the membrane potential to zero and charge of the membrane, more produ with walking baseline restoration of the membrane potential (repolyar and tion). The main role in these processes is played by ions Na + , depolarization is initially due to a slight increase in the permeability of the membrane for Na + ions . But the higher the degree of depolarization, the higher the permeability of sodium channels becomes, the more sodium ions enter the cell, and the higher the degree of depolarization. During this period not only occurs removed and the potential difference to zero voltage, but also the change of polarization IU m brane – at the height of the peak PD inner membrane surface is charged n of positively with respect to the outside. Repolarization processes are associated with an increase in the output of K + ions from the cell . through the opened channels. In general, it should be noted that the generation of action potential is a complex process, based on a coordinated change in the permeability of the plasma membrane for two or three basic ions ( Na + , K + and Ca + + ). The basic condition for the excitation of the excitable cells is reduced e of its membrane potential depolarization to a critical level (FPR). Any irritant or agent capable of reducing the membrane preparation . the potential of an excitable cell to a critical level of depolarization, is able to excite this cell. As soon as the MP reaches the level of the ASC, the process will continue to own and lead to the discovery of sodium kan and fishing, that is. e. to generate a full-fledged PD. If the membrane potential is not up to tignet this level, in the best case, there the so-called s Vai local potential (local response).
In certain excitable tissue membrane potential value of Bp e Meni not constant – it decreases periodically (ie. e. occurs Sponta n depolari-) and reaches independently ASCs, whereby the spontaneous excitation occurs, after which a membrane potential- and Al is reduced to the initial level, and then the cycle repeats. This property is called automatism . However, for excitation bol s shinstva excitable cells must have the external (otnosh e NIJ to the cells) stimulus.