The hyperpolarisation-mediated Ca2+ spike is proportional to inward current. The effects of hyperpolarisation-mediated currents are described as a function of inward current magnitude. The computational calculations predict that in the presence of hyperpolarisation induced currents, the ciliary system always generates Ca2+ impulses proportional to the applied inward current in both positive (A) and negative (B) ranges of values. The comparison of phase diagrams in the presence (C) and absence (D) of the hyperpolarisation-induced current vCah suggests that the Ca2+ spike generation in response to inward current alteration is due to the hyperpolarisation-mediated currents. In the absence of hyperpolarisation the solution becomes unstable with a limit cycle and the system undergoes sustained oscillations (D).