2 Neuroscience2.4 Cells
2.4.4 Glial function
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Written by Resident Doctor Committee · Published
New in the 2027 syllabus
The College added this topic for exams from January 2027.
What glia do
Glia are active partners of neurones, not passive packing material. They keep the environment around neurones stable so that neurones can signal. They also help regulate synapses and respond to injury.
Cell | Main location | Functions |
|---|---|---|
Astrocyte | Central nervous system | Buffers potassium outside cells, clears neurotransmitters and supports metabolism |
Oligodendrocyte | Central nervous system | Myelinates segments of several axons and supports axonal metabolism |
Microglial cell | Central nervous system | Surveys the tissue, removes debris and takes part in synaptic remodelling |
Ependymal cell | Lining of the ventricles | Supports the boundary with cerebrospinal fluid (CSF); its cilia help move the fluid |
Schwann cell | Peripheral nervous system | Myelinates one axonal segment, or supports unmyelinated fibres |
Satellite glial cell | Peripheral ganglia | Regulates the environment around neuronal cell bodies |
How glia work
Astrocytes take up glutamate, which stops it building up. They convert it to glutamine, which neurones can reuse as a precursor.
The blood-brain barrier depends on tight junctions between endothelial cells (the cells lining blood vessels). Astrocyte endfeet, pericytes and other parts of the neurovascular unit support it.
Myelin loss slows or blocks saltatory conduction, where the impulse jumps between gaps in the myelin. Damage to the support that oligodendrocytes give axons can also stop the axon surviving.
Microglia come mainly from progenitor cells in the embryonic yolk sac. Depending on the context, they can protect tissue or damage it. Activated microglia do not point to one specific disease.
CSF is mostly made by the specialised epithelium of the choroid plexus. Do not treat the ordinary ependymal cells lining the ventricles as its only source.
Clinical links and traps
Complement-associated pruning links immune signalling with the removal of synapses. A group-level association with psychosis does not establish the cause of psychosis in any one person.
Reactive gliosis means the changes glia undergo after injury. Raised glial markers can reflect repair, inflammation or tissue damage, not a single mechanism.