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72 lines
1.3 KiB
72 lines
1.3 KiB
2 years ago
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NEURON {
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SUFFIX capmp
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USEION ca READ cao, ica, cai WRITE cai, ica
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RANGE tau, width, cabulk, ica, pump0
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}
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UNITS {
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(um) = (micron)
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(molar) = (1/liter)
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(mM) = (millimolar)
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(uM) = (micromolar)
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(mA) = (milliamp)
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(mol) = (1)
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FARADAY = (faraday) (coulomb)
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}
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PARAMETER {
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width = 0.1 (um)
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tau = 1 (ms)
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k1 = 5e8 (/mM-s)
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k2 = 0.25e6 (/s)
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k3 = 0.5e3 (/s)
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k4 = 5e0 (/mM-s)
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cabulk = 0.1 (uM)
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pump0 = 3e-14 (mol/cm2)
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}
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ASSIGNED {
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cao (mM) : 2
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cai (mM) : 100e-6
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ica (mA/cm2)
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ica_pmp (mA/cm2)
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ica_pmp_last (mA/cm2)
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}
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STATE {
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cam (uM) <1e-6>
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pump (mol/cm2) <1e-16>
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capump (mol/cm2) <1e-16>
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}
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INITIAL {
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ica = 0
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ica_pmp = 0
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ica_pmp_last = 0
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SOLVE pmp STEADYSTATE sparse
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}
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BREAKPOINT {
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SOLVE pmp METHOD sparse
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ica_pmp_last = ica_pmp
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ica = ica_pmp
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}
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KINETIC pmp {
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~ cabulk <-> cam (width/tau, width/tau)
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~ cam + pump <-> capump ((1e7)*k1, (1e10)*k2)
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~ capump <-> cao + pump ((1e10)*k3, (1e10)*k4)
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ica_pmp = (1e-7)*2*FARADAY*(f_flux - b_flux)
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: ica_pmp_last vs ica_pmp needed because of STEADYSTATE calculation
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~ cam << (-(ica - ica_pmp_last)/(2*FARADAY)*(1e7))
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CONSERVE pump + capump = (1e13)*pump0
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COMPARTMENT width {cam} : volume has dimensions of um
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COMPARTMENT (1e13) {pump capump} : area is dimensionless
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COMPARTMENT 1(um) {cabulk}
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COMPARTMENT (1e3)*1(um) {cao}
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cai = (0.001)*cam
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}
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