Leg motor neurons
systemDescending and motor neuronsspeciesD. melanogaster3D view60 of 626 cellssources4
Leg motor neurons have their cell bodies and dendrites in the fruit fly’s ventral nerve cord and send their axons to the muscles of the legs. About 50 motor neurons control each leg.
| Also known as | Leg MNs · Leg motoneurons |
|---|---|
| Region | Ventral nerve cord (thoracic ganglia); axons end on leg muscles |
| System | Descending and motor neurons |
| In the display bundle | 60 of the 626 reconstructed neurons in the site’s MaleCNS display bundle, which shows 626 of the model’s 166,700 neurons: Acc. ti flexor MN 6, Acc. tr flexor MN 4, Fe reductor MN 2, ltm MN 3, ltm1-tibia MN 2, ltm2-femur MN 5, MNhl02 1, MNhl60 1, MNhl62 1, MNhl64 1, MNhl65 1, MNml78 1, MNml79 1, MNml80 1, MNml82 1, Pleural remotor/abductor MN 3, Sternal adductor MN 1, Sternal posterior rotator MN 3, Sternotrochanter MN 1, Ta levator MN 1, Tergopleural/Pleural promotor MN 1, Tergotr. MN 3, Ti extensor MN 2, Ti flexor MN 5, Tr extensor MN 1, Tr flexor MN 7, untyped 1 |
What they are
About 50 motor neurons operate each fly leg (Azevedo et al., 2020). They are born from at least 11 neuroblast lineages, two of which generate most of them; each is born at a characteristic time, from a specific lineage, and has a stereotyped dendritic architecture (Baek and Mann, 2009).
Where they sit
They lie in the thoracic part of the ventral nerve cord, which in an adult female contains roughly 14,600 neuronal cell bodies and 45 million synapses (Azevedo et al., 2024). Most cell-type names in this display bundle give the muscle a neuron controls, such as the tibia flexor (Ti flexor MN) or the trochanter extensor (Tr extensor MN).
What they do
Each leg motor neuron controls a particular range of force and speed. Recordings from the tibia flexor motor neurons show that they are recruited in a fixed order, from neurons producing small, slow movements for posture to those producing large, fast movements for running or escape, the same size principle described in other animals (Azevedo et al., 2020).
A connectome of the female nerve cord mapped leg and wing motor neurons to their muscles and identified circuits that coordinate leg and wing movements during takeoff (Azevedo et al., 2024). In the male nerve cord connectome, direct connections from descending neurons onto motor neurons are infrequent, and communities of interneurons are putatively linked to walking, flight and the coordination of wings and legs (Cheong et al., 2026).