The number and types of ionic channels characterize the membranes. Sodium, potassium, chloride, calcium and calcium-dependant potassium channels are only some of the channel types involved in the excitation processes. The gating mechanism also depends on the concentration of transmitters and several other parameters. This situation seems to be confusing when trying to model the effects of electrostimulation. Fortunately, functional electrostimulation is concerned with the excitation of nerve and muscle fibers but not with synapses; therefore, we can exclude the difficulties coming from the transmitters and other chemical influences. For most of the applications, we can even neglect the differences in ionic concentrations resulting from high membrane activities. For the remaining differences in membrane behavior, which are found in fibers of interest, we find several models in literature. Besides the HH model we will be concerned in this chapter with the Frankenhaeuser-Huxley Model, which was introduced for myelinated axons, and finally we will study models for mammalian nerves which are interesting because only sodium and leakage currents are involved.
KeywordsPotassium Channel Refractory Period Potassium Current Myelinated Axon Excitation Process
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