AXON — Synapse

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What “Activate synapse” shows

Pressing Activate synapse runs a didactic sequence of chemical synaptic transmission (not a literal molecular dynamics simulation, but the order matches textbooks). 1. Presynaptic excitation — the model animates activity sweeping toward the bouton, standing in for an action potential invading the terminal and depolarising the presynaptic membrane. 2. Calcium entry — Ca²⁺ influx near the active zone is shown as a local rise inside the terminal. In real synapses, voltage-gated Ca²⁺ channels cluster opposite docked vesicles; the resulting microdomain is what permits release on millisecond timescales. 3. Vesicle docking and fusion — primed vesicles approach the active-zone disc and merge with the membrane (exocytosis). Each vesicle releases a “quantum” of neurotransmitter: that is the physical meaning of quantal release. 4. Cleft diffusion — transmitter molecules cross the ~20 nm synaptic cleft by diffusion and reach postsynaptic receptors. Identity of the transmitter (here stylised) determines excitation versus inhibition in the target cell. 5. Receptor binding and postsynaptic response — binding opens or modulates ion channels; the scene shows receptor-side binding pulses and membrane/spine responses as a simplified readout of that chemistry becoming electricity again. Auto, when enabled, repeats the full sequence on a timer so you can watch the cycle without clicking each time.

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