Tonic firing → bursting → quiescence with slow Ca²⁺ current
Extended Hodgkin-Huxley model with a slow Ca²⁺-activated K⁺ current produces bursting.
The fast Na⁺/K⁺ dynamics generate spikes; Ca²⁺ accumulates during bursts and activates
a slow K⁺ current I_KCa that terminates the burst. Recovery of Ca²⁺ then allows the
next burst to begin — square-wave bursting (Hindmarsh-Rose style).