A minimal model is presented to explain changes in frequency, shape, and amplitude of Ca 2+ oscillations in the neuroendocrine melanotrope cell of Xenopus Laevis . It describes the cell as a plasma membrane oscillator with influx of extracellular Ca 2+ via voltage-gated Ca 2+ channels in the plasma membrane. The Ca 2+ oscillations in the Xenopus melanotrope show specific features that cannot be explained by previous models for electrically bursting cells using one set of parameters. The model assumes a K Ca -channel with slow Ca 2+ -dependent gating kinetics that initiates and terminates the bursts. The slow kinetics of this channel cause an activation of the K Ca -channel with a phase shift relative to the intracellular Ca 2+ concentration. The phase shift, together with the presence of a Na + channel that has a lower threshold than the Ca 2+ channel, generate the characteristic features of the Ca 2+ oscillations in the Xenopus melanotrope cell.