All diagrams in synapses and receptor signalling
Release and vesicle recycling
Electrical activity, calcium entry and vesicle fusion are distinct steps. Vesicle membrane recycling is different from amino-acid recycling.
Release and vesicle recycling
Scoped educational mechanism
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At chemical synapses, action potentials and presynaptic calcium entry can trigger fusion of prepared vesicles. Calcium-sensing proteins and the SNARE machinery participate in release. Membrane retrieval and vesicle preparation permit reuse, but release and recycling comprise multiple processes rather than one invariant conveyor belt. Firing rate, vesicle loading, the size of the ready pool and release probability are separate controls. The diagram illustrates established synaptic physiology and does not locate an ADHD-specific release defect.
- Ready vesicle → Exocytosis: ready for fusion
- Calcium signal → Exocytosis: Ca2+ trigger
- Exocytosis → Membrane retrieval: retrieval
- Membrane retrieval → Vesicle preparation: reuse
- Vesicle preparation → Ready vesicle: refill
What the diagram shows
At chemical synapses, action potentials and presynaptic calcium entry can trigger fusion of prepared vesicles. Calcium-sensing proteins and the SNARE machinery participate in release. Membrane retrieval and vesicle preparation permit reuse, but release and recycling comprise multiple processes rather than one invariant conveyor belt. Firing rate, vesicle loading, the size of the ready pool and release probability are separate controls. The diagram illustrates established synaptic physiology and does not locate an ADHD-specific release defect.