axons are said to have "somatic origin". Some axons with somatic origin have a "proximal" initial segment adjacent the axon hillock, while others have a "distal" initial segment, separated from the soma by an extended axon hillock. See also Electrophysiology Ganglionic eminence Giant axonal neuropathy Neuronal tracing Pioneer axon References External links "Slide 3 Spinal cord" Neurohistology