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Vagal Brake on the Sinoatrial Node

Interactive model of how vagal (parasympathetic) tone slows the heart: acetylcholine activates IKACh and suppresses the funny current in SA node pacemaker cells, hyperpolarizing the diastolic potential and flattening its slope. Adjust vagal and sympathetic tone, toggle respiratory sinus arrhythmia, and trigger a vagal burst.

Medicine & Biophysics3DModerate60 FPS📱 Mobile-adapted⇄ 2D version

The sinoatrial (SA) node sets heart rate by depolarizing spontaneously between beats, and the autonomic nervous system tunes that rate by reshaping the depolarization itself. This simulator models the two real ionic mechanisms behind parasympathetic (vagal) slowing — acetylcholine-gated I_KACh hyperpolarizing the maximum diastolic potential, and reduced cAMP flattening the funny-current-driven phase-4 slope — alongside sympathetic acceleration, respiratory sinus arrhythmia, and a triggerable vagal reflex burst. A cluster of SA node pacemaker cells pulses with each beat, ACh release from a modeled vagus nerve fiber tracks vagal tone, and a live oscilloscope trace shows the actual diastolic ramp and action potential shape changing under your control.

⚙ Under the hood

Interactive model of how vagal tone slows the heart: acetylcholine activates IKACh and suppresses the funny current in SA node pacemaker cells, hyperpolarizing the diastolic potential and flattening its slope, lengthening the RR interval.

cardiologyautonomic nervous systemsinoatrial nodevagal toneaction potentialheart rate

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