| 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: | presynaptic membrane |
|---|---|
| Synonyms: | pre-synaptic membrane, presynaptic plasma membrane |
| Definition: | A specialized area of membrane of the axon terminal that faces the plasma membrane of the neuron or muscle fiber with which the axon terminal establishes a synaptic junction; many synaptic junctions exhibit structural presynaptic characteristics, such as conical, electron-dense internal protrusions, that distinguish it from the remainder of the axon plasma membrane. |
| Ontology: | GO: Cellular Component [GO:0042734] QuickGO AmiGO |