Ribbon synapse

Ribbon synapse is a type of synapse linking some particular neuronal cells, which have unique features, such as their morphology, mechanisms of multivesicular release and calcium channel positioning which promote high speed of neurotransmitter release and an ongoing cycle of exocytosis and endocytosis in response to graded changes of membrane potential.

These features specialise the ribbon synapse to enable extremely fast, precise and sustained neurotransmission; which are critical for the perception of complex senses such as vision and hearing. Therefore ribbon synapses are found in retinal photoreceptor cells, vestibular organ receptors, cochlear hair cells and retinal bipolar cells.

The "ribbon" or presynaptic dense body is a unique structure at the synapse's active zone, hovering several nanometers above the presynaptic membrane and tethering 100 or more synaptic vesicles. Each presynaptic cell can have from 10 to 100 ribbons tethered to it, raising the total count to 1000-10000 vesicles.