GapjunctFIG 8: "Hub and spoke" gap junction system.
Cells are ordered into four layers to emphasize information flow from sensors to two subgroups of interneurons, and then to motor neurons and muscles (cf. Macosko et al, 2009). Some connections utilize both chemical (arrows) and electrical contacts in parallel, but in many cases gap junctions (shown in red) are the only direct link between nonequivalent cells in this circuit. The hub interneuron is thought to gather/compare different sensory stimuli in a common path before allowing that information to flow either directly to head muscles, or to the command interneurons (AVA, AVB) of the ventral nerve cord. Triangles represent sensory neurons, hexagons represent interneurons, circles represent motor neurons, and rhomboids represent bodywall muscles.
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