| Name: | secondary motor neuron |
|---|---|
| Synonyms: | secondary motoneuron |
| Definition: | 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. |
| Ontology: | Anatomy Ontology [ZFA:0009247] |
| Name: | nucleus |
|---|---|
| Synonyms: | cell nucleus, horsetail nucleus |
| Definition: | A membrane-bounded organelle of eukaryotic cells in which chromosomes are housed and replicated. In most cells, the nucleus contains all of the cell's chromosomes except the organellar chromosomes, and is the site of RNA synthesis and processing. In some species, or in specialized cell types, RNA metabolism or DNA replication may be absent. |
| Ontology: | GO: Cellular Component [GO:0005634] QuickGO AmiGO |