Basic Neurosciences · Paper A
Neuroglia functions
Exam questions on neuroglia hinge on matching each glial cell to its one job, because the same 'which cell does this' trap gets recycled across multiple sclerosis, Guillain-Barré and CSFCerebrospinal fluid, the fluid that cushions the brain and spinal cord.Read more → questions. Glia are the brain's support cells, far outnumbering neurons, but unlike plain 'glue' each type does one specific job. Take the classic trap: which cell is destroyed in multiple sclerosis? The answer is the oligodendrocyte, not the Schwann cell, which does the equivalent job outside the brain and spinal cord. Learning each glial cell's ONE key job is enough to answer most exam questions on this topic.
Astrocytes are the most numerousthey form the blood-brain barrierA protective filter of tightly packed cells that limits which substances can pass from the blood into the brain.Read more →, mop up excess potassium, recycle the transmitter glutamate, support neurons metabolically, and form scar tissue after injury. Oligodendrocytes wrap myelinThe fatty insulating sheath around nerve fibres that speeds up electrical signals.Read more → (the insulating sheath that speeds nerve signals) around CENTRAL nerve fibres, one cell myelinates several at once; they are the target in multiple sclerosis. Microglia are the brain's resident immune cells, clearing debris and reacting to injury. Take a stem describing a peripheral nerve injury and asking which cell remyelinates it: the two 'myelinating' cells, oligodendrocytes centrally and Schwann cells peripherally, are the pair most likely to be swapped in a question of this kind. E.g., a patient with optic neuritis from multiple sclerosis has lost oligodendrocytes, not the Schwann cells that remyelinate peripheral nerves.
Neurons (nerve cells that carry electrical signals) get all the attention, but they cannot survive, signal, or even form a working brain without support cells around them. The exam tests neuroglia because a huge share of neurological and psychiatric disease (multiple sclerosis, Guillain-Barré syndrome, brain tumours) actually attacks the SUPPORT cells, not the neurons themselves. Knowing which glial cell does which job is therefore the fastest way to work out which disease a stem is describing.
Neuroglia, usually shortened to glia, are the non-neuronal cells of the nervous system. They outnumber neurons several times over, yet unlike neurons they do not carry electrical signals over long distances. Instead, each type of glial cell has ONE main practical job: physical support, insulation, immune defence, or fluid circulation. Learning that one job per cell type answers most exam questions.
The biggest trap is confusing the two myelinating cell types. Myelin (a fatty insulating sheath that speeds up nerve signal conduction) is made by TWO different cells depending on location: oligodendrocytes in the central nervous system (brain and spinal cord) and Schwann cells in the peripheral nervous system (nerves outside the brain and spinal cord). Mixing these up is the single most common error on this topic.
A neuron is metabolically expensive and physically fragile: it needs a stable chemical environment, a blood supply it cannot maintain alone, and, for long axons (the long fibre that carries a neuron's signal), insulation to conduct signals fast enough to be useful. Evolution solved this by dividing the labour: one set of cells manages the chemical environment and barrier function, one insulates the wiring, one handles clean-up and defence, and one manages the fluid system that cushions and nourishes the whole brain. Each glial type below is a solution to one of these separate problems.
Astrocytes are the most numerous glial cell. They form the (a selective barrier that keeps most substances in the blood from reaching brain tissue), mop up excess potassium ions released during neuron firing, recycle the glutamate (a chemical messenger neurons use to signal each other) so it doesn't build up and become toxic, support neurons metabolically by supplying nutrients, and form scar tissue () after brain injury.
Oligodendrocytes wrap around CENTRAL nerve fibres. One oligodendrocyte reaches out and myelinates several different axons at once, unlike its peripheral counterpart. Oligodendrocytes are the cell destroyed in multiple sclerosis (an autoimmune disease where the immune system attacks central myelin), which is why MS causes patchy, unpredictable neurological symptoms wherever myelin is lost.
Microglia are the brain's resident immune cells, derived from a different embryonic origin (mesoderm) than the other glia. They constantly patrol for debris, dying cells and pathogens, and become activated after injury or infection to clear damaged material: the brain's built-in clean-up crew.
Ependymal cells line the ventricles (the brain's fluid-filled chambers) and help circulate cerebrospinal fluid, or CSF (the clear fluid that cushions the brain and spinal cord and carries nutrients and waste). A specialised group of ependymal cells forms the choroid plexus, the structure that actually produces CSF.
In the peripheral nervous system, two further cell types take over similar jobs. Schwann cells make around peripheral nerve fibres, but each Schwann cell wraps only ONE segment of ONE axon, unlike an oligodendrocyte's one-to-many arrangement. Satellite cells surround and support the cell bodies of neurons sitting in peripheral ganglia (clusters of nerve cell bodies outside the brain and spinal cord).
The exam's favourite swap is oligodendrocyte versus Schwann cell: both myelinate, but location decides which one: central tissue (brain, spinal cord, optic nerve) means oligodendrocyte, peripheral tissue means Schwann cell. For example, a question describing demyelination in the optic nerve points to an oligodendrocyte problem, while the same picture in a peripheral limb nerve points to a Schwann cell problem. A second common swap is astrocyte versus microglia: astrocytes are structural and metabolic support, while microglia are strictly the immune/clean-up cell: a stem describing "reacting to injury by clearing debris" points to microglia, not astrocytes.
In multiple sclerosis, diagnosis rests on the McDonald criteria, which require evidence of demyelinating lesions separated in both time and space, most often shown on MRI (magnetic resonance imaging) as characteristic white-matter plaques, supported by cerebrospinal fluid analysis showing oligoclonal bands (a marker of intrathecal antibody production). In Guillain-Barré syndrome, the peripheral equivalent, nerve conduction studies show slowed conduction consistent with Schwann cell demyelination, and classically shows raised protein with a normal cell count.
For multiple sclerosis, NICE guidance (NG220) supports disease-modifying therapies such as interferon-beta or ocrelizumab to reduce relapse frequency, with high-dose corticosteroids for acute relapses. For Guillain-Barré syndrome, management is intravenous immunoglobulin or plasma exchange, per UK neurology guidelines, alongside close monitoring of respiratory function since the diaphragm's peripheral nerves can be affected.
Whenever a stem names a specific location (optic nerve, spinal cord, a named peripheral nerve), first decide central or peripheral, then pick the myelinating cell for that side: oligodendrocyte centrally, Schwann cell peripherally. That two-step check resolves most glial-cell questions instantly.
Each glial cell has one job: astrocytes support, oligodendrocytes and Schwann cells myelinate (central versus peripheral), microglia defend, ependymal cells circulate , and disease usually attacks just one of them.