Thank you for submitting comments. Your input has been emailed to ZFIN curators who may contact you if
additional information is required.
Oops. Something went wrong. Please try again later.
secondary motor neuron
secondary motoneuron, ZFA:0000584
Motor neurons that develop several hours later than primary motoneurons and sprout axons several hours after the primary motor growth cones have extended to the periphery. They have smaller cell bodies and are located more ventrally and laterally in the spinal cord than primary motoneurons. Axons usually project directly out of the spinal cord with no apparent contact with the Mauthner axon and are positioned lateral to the Mauthner axon in their path to the ventral root. Secondary motoneurons have smaller fields, which can overlap one another, and innervate many fewer muscle fibers than primary motoneurons.