| Popis: |
The myelinated nerve fiber, stimulated by a current generator, is modeled as a straight thin wire antenna. The model is based on the thin wire approximation and the corresponding homogenous Pocklington integro-diferential equation for the perfectly conducting wire in a lossy unbounded homogenous space. Pocklington integro-differential equation in the frequency domain is numerically solved by means of the Galerkin Bubnov Indirect Boundary Element Method(GB-IBEM). By solving the Pocklington integro-differential equation, the intracellular current distribution along the myelinated nerve fiber is obtained. The intracellular current results in the frequency domain are transferred into the time domain by the Matlab IFFT algorithm. Transmembrane voltage is calculated by including the intracellular current results, which are obtained by means of the thin wire antenna model, into the CRRSS transmission line model. The passive and active nerve fiber responses are analyzed for the nerve fibers of different lengths, stimulated with different types of waveforms. The activated node of Ranvier is modeled as a thin wire junction where additional current source, representing the corresponding ionic current of the activated node, is placed. The additional current source is put in action when the threshold current, defined with the strength-duration curve, is reached. The strength-duration curve, which is a relationship between a strength of a stimulus and its duration for producing minimal excitation, is defined from the CRRSS model. The results are verified by comparison with the CRRSS model, wherever possible. |
