{ diff(x1, t) = k25*x2 + k42*x12 + k40*x10 - (k10*x3*x1 - k10*k12*x5 + k14*x4*x1 - k15*x6),
  diff(x2, t) = k23*x6 - (k25*x2 + k30*x11*x2 - k31*x12 + k33*x9*x2 - k34*x10),
  diff(x3, t) = (-1)*(k6*x3*piecewise(k2/(1 + exp((-80)*(t - k3 - 1/20))), and(t < k3 + 3/20, t >= k3), k2, t >= k3 + 3/20, 0) - k6*k8*x4 + k10*x3*x1 - k10*k12*x5),
  diff(x4, t) = k6*x3*piecewise(k2/(1 + exp((-80)*(t - k3 - 1/20))), and(t < k3 + 3/20, t >= k3), k2, t >= k3 + 3/20, 0) - k6*k8*x4 + k23*x6 - (k14*x4*x1 - k15*x6),
  diff(x5, t) = k10*x3*x1 - k10*k12*x5 - (k17*piecewise(k2/(1 + exp((-80)*(t - k3 - 1/20))), and(t < k3 + 3/20, t >= k3), k2, t >= k3 + 3/20, 0)*x5 - k17*k19*x6),
  diff(x6, t) = k14*x4*x1 - k15*x6 - k21*x6 + k17*piecewise(k2/(1 + exp((-80)*(t - k3 - 1/20))), and(t < k3 + 3/20, t >= k3), k2, t >= k3 + 3/20, 0)*x5 - k17*k19*x6 - k23*x6,
  diff(x7, t) = k21*x6,
  diff(x8, t) = 1/(k54*3011/5)/(1/(k54*k55))*(k44*x9*k4/(k45/(1/(k54*3011/5)/(1/(k54*k55))) + k4) + k47*x10*k4/(k48/(1/(k54*3011/5)/(1/(k54*k55))) + k4)) - k50*x8,
  diff(x9, t) = k27*x11*x13 - k28*x9 + k40*x10 - (k33*x9*x2 - k34*x10),
  diff(x10, t) = k33*x9*x2 - k34*x10 + k36*x12*x13 - k36*k38*x10 - k40*x10,
  diff(x11, t) = k42*x12 - (k30*x11*x2 - k31*x12 + k27*x11*x13 - k28*x9),
  diff(x12, t) = k30*x11*x2 - k31*x12 - (k36*x12*x13 - k36*k38*x10 + k42*x12),
  diff(x13, t) = 1/(k54*3011/5)/(1/(k54*k55))*(-1)*(k27*x11*x13 - k28*x9 + k36*x12*x13 - k36*k38*x10) }