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Pacemaker Cell Automaticity: The Funny Current

Interactive single-cell SA-node model: watch HCN (funny current, If), T-type calcium and delayed-rectifier potassium channels drive spontaneous diastolic depolarization and rhythmic firing, with autonomic tone and ivabradine controls.

Medicine & Biophysics3DAdvanced60 FPS📱 Mobile-adapted⇄ 2D version

Sinoatrial node cells generate the heartbeat's underlying rhythm without any external trigger, because their membrane never truly rests: HCN channels carrying the "funny current" (I_f), a low-threshold T-type calcium window current, and the slow deactivation of the delayed-rectifier potassium current together produce a spontaneous diastolic depolarization that autonomously climbs to threshold and fires. This simulator integrates a reduced ion-channel model of a single pacemaker cell in real time, visualizing HCN, Ca²⁺ and K⁺ channel populations on the cell membrane and their open probabilities, while sliders for HCN channel density and autonomic (sympathetic/vagal) tone plus an ivabradine toggle let you explore exactly how each mechanism speeds or slows the intrinsic heart rate.

⚙ Under the hood

A real-time single-cell model of a sinoatrial node pacemaker cell, showing how HCN channels (the funny current, If), a T-type calcium window current and delayed-rectifier potassium deactivation together generate spontaneous diastolic depolarization and set the intrinsic heart rate.

cardiologyelectrophysiologyion-channelsHCN-channelsheart-rhythmautonomic-nervous-system

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install