A Under What Conditions Can Quasi Stationarity Be Assumed For A Time Varying Electromagnetic Field Problem Such As Thos 1 (19.99 KiB) Viewed 30 times
a) Under what conditions can quasi-stationarity be assumed for a time-varying electromagnetic field problem such as those encountered in electrophysiology, EEG, ECG etc.? Determine whether these conditions are valid for typical conductivity and relative permittivity values of 0.2 Sm' and 4.5x10 of muscle tissue at 1 kHz. 4 b) A bipolar electrode is placed on the skin surface, 20 mm directly above a muscle fibre that lies parallel to the surface. The two electrodes of the bipolar pair are placed 60 mm and 70 mm from the muscle fibre end-plate, along the direction of the fibre. When the muscle fibre is stimulated at time t = 0 ms, an action potential propagates in both directions along the fibre with a uniform conduction velocity of 5 m/s.
What is the voltage detected at the bipolar electrode at time t = 20 ms? The muscle fibre may be assumed to lie in a homogenous, isotropic volume conductor of infinite extent. The transmembrane current may be represented as a balanced tripole with source strengths I., I and I; equal to 328 14, -388 nA and 60 nA respectively. The separation between II and Iz is 0.90 mm and the conductivity of the muscle tissue, ce, is 2.44 S/m. It can be assumed that the contribution from the action potential propagating in the direction away from the electrode is negligible. C) If the muscle tissue was assumed instead to be cylindrically anisotropic, what effect would this have on the amplitude and shape of the extracellular action potential? Give an approximate value for the ratio of longitudinal to transverse conductivity of muscle tissue.
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