[ Eq(Derivative(x1, t), (1*k21*k1*Piecewise((0, And(Ge(t, 0), Lt(t, 5))), (Piecewise((1, And(Ge(t, 5), Lt(t, 10))), (0, True)), True))/(k3 + Piecewise((0, And(Ge(t, 0), Lt(t, 5))), (Piecewise((1, And(Ge(t, 5), Lt(t, 10))), (0, True)), True))) + (-1)*k21*k4*x1)/k21),
  Eq(Derivative(x2, t), (1*k21*k5*Piecewise((1, And(Ge(t, 0), Lt(t, 5))), (0, True))/(k7 + Piecewise((1, And(Ge(t, 0), Lt(t, 5))), (0, True))) + (-1)*k21*k8*x2)/k21),
  Eq(Derivative(x3, t), (1*k21*k14*x1 + 1*k21*k15*x2 + (-1)*k21*k16*x3)/k21),
  Eq(Derivative(x4, t), (1*k21*k17*x7 + 1*k21*k18*x3 + (-1)*k21*k19*x4)/k21),
  Eq(Derivative(x5, t), (1*k21*k11*x2*x7 + (-1)*k21*k20*x5)/k21),
  Eq(Derivative(x7, t), (1*k21*k10*(k13 - x7 - x5)*x1 + 1*k21*k9*(k13 - x7 - x5)*x4 + (-1)*k21*k12*x7 + (-1)*k21*k11*x2*x7)/k21) ]