Editing Motor neuron (section)

=== Synaptic input to motor neurons ===
Motor neurons receive synaptic input from premotor neurons. Premotor neurons can be 1) [[Spinal interneuron|spinal interneurons]] that have cell bodies in the spinal cord, 2) [[Sensory neuron|sensory neurons]] that convey information from the periphery and [[Reflex|synapse directly onto motoneurons]], 3) [[Descending neuron|descending neurons]] that convey information from the [[Corticomotor neuron|brain]] and [[brainstem]]. The synapses can be [[Excitatory synapse|excitatory]], [[Inhibitory synapse|inhibitory]], [[Gap junction|electrical]], or [[Stomatogastric nervous system|neuromodulatory]]. For any given motor neuron, determining the relative contribution of different input sources is difficult, but advances in [[connectomics]] have made it possible for [[Drosophila melanogaster|fruit fly]] motor neurons. In the fly, motor neurons controlling the legs and wings are found in the [[ventral nerve cord]], homologous to the [[spinal cord]]. Fly motor neurons vary by over 100X in the total number of input synapses. However, each motor neuron gets similar fractions of its synapses from each premotor source: ~70% from neurons within the VNC, ~10% from descending neurons, ~3% from sensory neurons, and ~6% from VNC neurons that also send a process up to the brain. The remaining 10% of synapses come from neuronal fragments that are unidentified by current image segmentation algorithms and require additional manual segmentation to measure.<ref>{{Cite journal |last1=Azevedo |first1=Anthony |last2=Lesser |first2=Ellen |last3=Mark |first3=Brandon |last4=Phelps |first4=Jasper |last5=Elabbady |first5=Leila |last6=Kuroda |first6=Sumiya |last7=Sustar |first7=Anne |last8=Moussa |first8=Anthony |last9=Kandelwal |first9=Avinash |last10=Dallmann |first10=Chris J. |last11=Agrawal |first11=Sweta |last12=Lee |first12=Su-Yee J. |last13=Pratt |first13=Brandon |last14=Cook |first14=Andrew |last15=Skutt-Kakaria |first15=Kyobi |date=2022-12-15 |title=Tools for comprehensive reconstruction and analysis of Drosophila motor circuits |url=https://www.biorxiv.org/content/10.1101/2022.12.15.520299v1 |language=en |pages=2022.12.15.520299 |doi=10.1101/2022.12.15.520299|s2cid=254736092 }}</ref>