Perikaryon

Definition

The cytoplasmic portion of a neuron or glial cell surrounding the nucleus, excluding the cell processes (axons and dendrites); essentially the soma minus the nucleus. In arthropods, perikarya of sensory neurons are often clustered in peripheral ganglia or within sensory structures such as insect mechanoreceptors and arachnid slit sensilla, where their metabolic machinery supports high rates of signal transduction.

Etymology

Greek peri- (around) + karyon (nut, kernel, i.e., nucleus)

Example

In the Johnston's organ of Drosophila, the perikarya of chordotonal neurons reside distal to the cuticular cap structures, with dendritic processes extending toward the sensory cuticle and axons projecting toward the brain.

Synonyms

• perikaryal cytoplasm
• cytoplasmic soma

Related Terms

• soma
• Neuron
• ganglion
• Dendrite
• Axon
• Glial cell
• neuroplasm

Usage Notes

Distinguished from 'soma' or 'cell body,' which includes the nucleus; perikaryon refers specifically to the cytoplasmic region. The plural 'perikarya' is preferred in technical writing over 'perikaryons.' In arthropod histology, perikaryon size and staining properties vary with neuronal metabolic state and are used to identify functional neuron classes.