Integration in a Neuron: EPSPs, IPSPs, and Summation
A simplified but principled animation of dendritic integration. Graded potentials spread from each synapse,
attenuate and slow with distance, sum across space and time, and can trigger an action potential if the
membrane potential at the axon initial segment reaches threshold.
Keys: 1–6 load a preset, L the custom lab,
Space run/pause, R reset, ←/→ step 1 ms
(Shift for 5 ms), P presentation mode.
Tip: click the synapse buttons—or click directly on the synapse markers in the neuron—to fire them manually.
Manual firing is only practical at slow playback speeds.
Peak at AIS—
Peak at local site—
Threshold margin—
Action potential—
Preset demonstrations
Choosing a preset only loads it. Nothing fires until you press Run loaded preset.
LOADED PRESETDistal EPSP
Ready — press Run
Synapses and timing
Offsets are measured from the start of the trial. Equal offsets mean simultaneous firing;
E3 = 0 ms and E4 = 4 ms gives a 4-ms separation.
UseSynapseOffset
The loaded synapses are also outlined on the neuron before you run the trial.
Manual synapse firing
Click a synapse button—or the synapse itself on the neuron—to start a manual trial,
then add other synapses while the trial is running. Use a playback speed of 0.05× or slower.
Display and model options
Local recording site
Summation model
Spread visualisation
Colour palette
Slowed spread is a visual aid, not physics. Electrotonic spread is nearly
instantaneous; the voltage trace uses the real (fast) timing, so the glow will lag behind the trace.