start stage end stage MiP motor neuron A primary motor neuron that is part of the spinal cord. The axon turns caudally and dorsally, coursing between the surface of the spinal cord and the medial surface of the axial muscles to the dorsal median septum. The MiP axon then extends dorsally to the surface of the muscle, where it turns to arborize ventrally over the lateral surface of the axial muscle. zebrafish_anatomy 2009-06-18T04:02:28Z TAO:0005179 Ceri middle primary motoneuron This term is a leaf node in the zebrafish AO and is not in the CL. ZFA:0005179 primary motor neuron segmentation:14-19 somites adult