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lecar_eqs - “nuns uulu cecal 1 upoacu u bllllplt 1110061...

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Unformatted text preview: “nuns uulu cecal 1.)]. upoacu u bllllplt: 1110061 to explain the observed electrical be- havior of the barnacle muscle fiber (Morris and Lecar 1981). Their model involves only a fast activating Ca2+ current, a delayed rectifier K+ current, and a passive leak. They tested the model against a number of experimental conditions in which the interior of the fiber was perfused with the Ca2+ chelator EGTA in order to reduce activation of the KCa current. Their simulations provide a good explanation of their experimental measurements. The model translates into two equations: dV CE = —3Camoo(V _ VCa) _ gKW(V — VK) _ gL(V _ VT.) + Iapp: (230) dw _ ¢(Woo _ W) dt _ 1' l (2.31) Here mm is the fraction of voltage-dependent Ca2+channels open, and this is a function of voltage but not time. Furthermore, w is the fraction of open channels for the delayed rectifier K+ channels, and the conductances gL, goa, and gK are for the leak, Ca2+, and K+ currents, respectively. We use w rather than the previously used 1‘}; for the fraction of open channels for historical reasons. The functions ' mm = 0.5[1 + tanh((V — v1)/vz)], (2.32) woo = 0.5[1 + tanh((V — V3)/V4)], (2.33) 1' = 1/ cosh((V — v3)/(2 . 1/4)), (2.34) -——-————____________ Table 2.4 Morris—Lecar Oscillator Parameters (Type Ill ———________________ ZOMF/cmz —84 mV 8 mS/c:m2 120 mV 4.4 mS/cm2 —60 mV 2 mS/cm2 —1.2 mV 18 mV 2 mV 30 mV 0.04/ms ...
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