Two-Segment Electophysiological Model of Excitable Membrane of Paramecium

Abstract

Our goal in this paper is to design a two-segment electrophysiological model for Parameciumbased on the work of Hook and Hildebrand (1979, 1980). This model considers Paramecium divided into two segments. Both segments are assumed to obey Hook and Hildebrand equations. The aim of constructing this model is to consider theoretically how the free- swimming Parameciumresponses to the external electric stimulation, involving whether the organism is facing the anode or the cathode during the application of the electric pulse. We assume that there is an irregular distribution of Ca²⁺ and K⁺ channels on both segments. We have designed a computer program to illustrate the relationship between the distribution channels and swimming reversal time of the Paramecium. It is found that the reversal time depends on the precise distribution of Ca²⁺ and K⁺ channels. The relevant ratio of ionic channels distribution is found to be 74.8% and 25.2% for K⁺ and Ca²⁺,respectively over the cell anterior and vice versafor posterior.
Keywords: Paramecium; Potassium and calcium currents; Membrane potential; Ionic conductance; Ca²⁺ and K⁺ channels; Reversal time.