Gliala

Glia, or glial cells, are non-neuronal cells of the nervous system that provide structural and functional support for neurons. The term glia originates from the Greek for "glue," reflecting a historic view of their role in holding neural tissue together. The form gliala may appear in some languages or as an adjectival form, but in English the standard terms are glia or glial cells.

In the central nervous system, the major glial cell types are astrocytes, oligodendrocytes, microglia, and ependymal cells. In the peripheral nervous system, the main glia are Schwann cells and satellite glial cells. Each type has distinct roles in maintenance and defense of nervous tissue.

Functions include providing metabolic support to neurons, regulating extracellular ion and neurotransmitter levels, guiding development, and contributing to the blood-brain barrier and cerebral homeostasis. Oligodendrocytes and Schwann cells form myelin sheaths that insulate axons, speeding electrical signaling. Microglia act as immune cells, and astrocytes participate in synaptic modulation and repair.

Glial cells develop from neural progenitors in the CNS, while microglia originate from mesodermal precursors; Schwann cells and satellite cells derive from neural crest during development. Glial networks participate in activity-dependent plasticity and respond to injury through gliosis and scar formation.

Clinical relevance includes gliomas, tumors of glial origin, and gliosis after CNS injury. Glial dysfunction and maladaptive glial responses are linked to neurodegenerative and psychiatric conditions, making glia an active area of neuroscience research and therapeutic exploration.