Figure 3.

Minimal model of Chay and Keizer (CK model). A. Scheme of the CK model. The active phase (1) is sustained by the VDCCs and K_v channels, slowly increasing [Ca²⁺]_i. The K_Ca channels are activated, eventually repolarizing the membrane (2). During the silent phase (3), the VDCCs and K_v channels are closed and Ca²⁺ is extruded from the cell, inhibiting the activity of the K_Ca channels. The slow depolarization eventually activates the VDCCs and K_v channels, initiating a new burst. B. Fast bursting simulated with the CK model. Top: Membrane potential (black curve) and intracellular Ca²⁺ concentration ([Ca²⁺]_i, yellow curve). Bottom: Ca²⁺-dependent K⁺ (K_Ca) current.