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Flashcards in Glia Deck (38)
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What is the main role of glia?

To support neurons and communication.


Name the CNS glia

Macroglia, which are split into oligodendrocytes and astrocytes, and microglia.


Name the retinal glia



Name the cerebellum glia

Bergmann glia


Name the PNS glia

Schwann cells, satellite cells and enteric glial cells


What is the main role of oligodendrocytes?

To myelinate in the CNS


Where do they originate from?

From neuroepithelial cells in the VZ. They become radical glia with their cell bodies in the VZ and processes extending into the pial surface before dividing and differentiating to become neurons and glia.


Name the different areas of the neuroepithelium and where oligodendrocytes come from.

P0,P1,P2,PMN,P3,FP. Oligodendrocytes come from PMN.


What do these precursor cells in the ventral spinal cord express?

Olg2 Sox10 and Pdgfra


What do mature oligodendrocytes express?

Galactocerebroside (GC)


Name and explain the 3 stages of maturation of myelin sheaths.

1. Differentiation stimulated by axon contact
2. Ensheathment. Initiator processes extend and spiral along the axon.
3. Remodelling. Non ensheathment processes are lost and initial sheathments interact to form compact myelin.


Why myelinate?

Makes small axons faster by preventing Na+ concentration leaking out. Nodes of Ranvier also present means Na+ channels only there so enhanced velocity of action potential occurs.


What are the functions of astrocytes?

Structural support
maintaining the blood brain barrier
metabolic support
regulate extracellular ion concs and pH
remove neurotransmitters
participate in formation and elimination of synapses


Where are astrocytes found and what different types are there?

Everywhere in the CNS. Fibrous are long and sparse found in the white matter. Protoplasmic are short and numerously branched found in the grey matter.


Where do astrocytes originate from?

Radial glia but dont then travel as far. Remain in the cortex.


Explain the role of astrocytes in maintaining the blood brain barrier

Barrier allows selective absorption of substrates and restricts larger objects. vascular endothelial cells form it. Astrocytes' endfeet have receptors, transporters and channels to regulate the interference between the blood and the brain.


Explain the role of astrocytes in removing neurotransmitters from the extracellular space.

Glutamate is converted to glutamine by astrocytes and then released for re-uptake. Also release ATP which modulates synaptic transmission.


Where do microglia originate from?

From macrophages outside the CNS. Unrelated to other glia.


What is microglia's main function?

Brain's immune system.


Describe how the microglia proliferate.

Originate from myeloid linkage. Foetal macrophages enter neural tube at early embryonic stages and transform into embryonic microglia. Amoeboid microglia found in white matter and close to blood vessels/. Proliferate and move to cortex.


What state are microglia found in in a normal brain?

Ramified (resting)


Describe the activated state of microglia.

Processes retract and thicken
Cell body enlarges and moves towards site of damage
Reversible state induced by signals from otehr microglia, neurons or other glia


What is the Phagocytic state of microglia?

Occurs at synapse/neuron death.
signals come from dead/dying cells.


Where do Schwann cells originate from?

Neural crest cells which have come from the dorsal tube migrate out and form many differenct cells inc. schwann.


Describe the schwann cell lineage

Neural crest cell - precursor - immature schwann cells - either non myelinating schwann cell OR pro myelin schwann cell which becomes a myelinating schwann cell. Myelinating and non myelinating can swap between each other by going through the immature cell stage again.


Describe the role of non myelinating schwann cells

Surround bundles of small diamater axons
Support and separate axons
Express markers of immature schwann cells
Can myelinate experimentally


What happens with schwann cells at time of damage?

Move distal to point of damage
Phagocytose damage and employ macrophages to help
Rebuild around new axons but at a reduced thickness


What are satellite cells?

Flattened cells that cover nuerons in Dorsal root sensory ganglia and in sympathetic and parasympathetic ganglia.


What do olfactory sheathing cells do?

Envelop axons of the olfactory nerve


What covers axon terminals and the skeletal neuromuscular junction?

Terminal glia


Enteric glia are...?

Similar to astrocytes but found in the enteric nervous system.


Where are muller glia from?

Retinal nueroepithelial cells. They are the last glia to differentiate


Describe the three nuclear layers of the retina.

ONL - outer nuclear layer. Photoreceptors which sense light
INL - Inner nuclear layer. Three types of interneurons. Muller glia here but span all layers.
GCL - ganglions that send axons to the brain


What are the functions of muller glia?

-Act as optical fibres to guide light to photoreceptors
-Monitor retinal homeostasis - recycling transmitters, controlling ionic balance and releasing trophic factors.
-Participate in outer cone phagocytosis, contribute to their assembly and help to recycle chromophore.
- Can generate neurons under specific conditions


What is reactive gliosis?

Muller glia's response to damage which is to often proliferate (depending on severity) and to change their gene expression.


Where are bergmann cells found?

In the Purkinje layer of the cerebellum.


Describe bergmann glia in the mature cerebellum.

Unipolary astrocytes which extend long processes across all layers
From structural relationships with Purkinje cells.
Express gaba and glutamate transporters and assist in their removal.


Where do bergmann glia come from?

Neuroepithelial cells in the 4th ventricle and migrate through the mantle zone at the same time as Purkinje cells.