Dependence on initial values for steady-state. Plotted are steady-state values of ligand-bound receptor (R_EGF*) as a function of EGF-stimulation for different initial receptor levels R0. For R0 = 1.7 (orange), i.e. R0 < CDE0 + CIE0, the system reaches steady-state class I independently of EGF-stimulation, as seen from R_EGF* = 0. If R0 = 3 (green) or R0 = 5 (black), i.e. CDE0 + CIE0 < R0, the steady-state value of R_EGF becomes positive for EGF-stimulations higher than 2 (steady-state class II).