start stage end stage CaP motoneuron caudal primary motoneuron TAO:0009243 ZFA:0009243 zebrafish_anatomy CL:0000532 CAP motoneurons A primary motor neuron part of the spinal cord. The CaP motoneuron is found within 1 soma diameter of the ventral root. The axon of the CaP motoneuron extends ventrally from the ventral root, within the space between the notochord and the medial surface of the axial muscles. Below the notochord, the axon extends within the ventral median septum to the ventral edge of the axial muscles, where it turns dorsally and laterally to project over the lateral surface of the axial muscles. primary motor neuron unknown adult