Glia

Question 1

What is the main role of glia?

Answer 1

To support neurons and communication.

Question 2

Name the CNS glia

Answer 2

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

Question 3

Name the retinal glia

Answer 3

Muller

Question 4

Name the cerebellum glia

Answer 4

Bergmann glia

Question 5

Name the PNS glia

Answer 5

Schwann cells, satellite cells and enteric glial cells

Question 6

What is the main role of oligodendrocytes?

Answer 6

To myelinate in the CNS

Question 7

Where do they originate from?

Answer 7

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.

Question 8

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

Answer 8

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

Question 9

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

Answer 9

Olg2 Sox10 and Pdgfra

Question 10

What do mature oligodendrocytes express?

Answer 10

Galactocerebroside (GC)

Question 11

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

Answer 11

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.

Question 12

Why myelinate?

Answer 12

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.

Question 13

What are the functions of astrocytes?

Answer 13

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

Question 14

Where are astrocytes found and what different types are there?

Answer 14

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.

Question 15

Where do astrocytes originate from?

Answer 15

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

Question 16

Explain the role of astrocytes in maintaining the blood brain barrier

Answer 16

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.

Question 17

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

Answer 17

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

Question 18

Where do microglia originate from?

Answer 18

From macrophages outside the CNS. Unrelated to other glia.

Question 19

What is microglia’s main function?

Answer 19

Brain’s immune system.

Question 20

Describe how the microglia proliferate.

Answer 20

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.

Question 21

What state are microglia found in in a normal brain?

Answer 21

Ramified (resting)

Question 22

Describe the activated state of microglia.

Answer 22

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

Question 23

What is the Phagocytic state of microglia?

Answer 23

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

Question 24

Where do Schwann cells originate from?

Answer 24

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

Question 25

Describe the schwann cell lineage

Answer 25

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.

Question 26

Describe the role of non myelinating schwann cells

Answer 26

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

Question 27

What happens with schwann cells at time of damage?

Answer 27

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

Question 28

What are satellite cells?

Answer 28

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

Question 29

What do olfactory sheathing cells do?

Answer 29

Envelop axons of the olfactory nerve

Question 30

What covers axon terminals and the skeletal neuromuscular junction?

Answer 30

Terminal glia

Question 31

Enteric glia are...?

Answer 31

Similar to astrocytes but found in the enteric nervous system.

Question 32

Where are muller glia from?

Answer 32

Retinal nueroepithelial cells. They are the last glia to differentiate

Question 33

Describe the three nuclear layers of the retina.

Answer 33

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

Question 34

What are the functions of muller glia?

Answer 34

- 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

Question 35

What is reactive gliosis?

Answer 35

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

Question 36

Where are bergmann cells found?

Answer 36

In the Purkinje layer of the cerebellum.

Question 37

Describe bergmann glia in the mature cerebellum.

Answer 37

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.

Question 38

Where do bergmann glia come from?

Answer 38

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