Glia

Question 1

Describe the divisions of nueral cells

Answer 1

Neuronal cells(10%) or glia (90%)
Glia…macroglia or microglia(10-15%) or schwann cells
Macroglia…astrocytes (80%), oligodendrocytes (5%), ependymal cells(5%)

Question 2

Functions of astrocytes

Answer 2

Support - layer under pia
maintain homeostasis
NT uptake
BBB
Transport and metabolism
Injury etc

Question 3

Functions of Oligodendrocytes

Answer 3

30-50 fine processes and as flat sheets wind around axons to form myelin sheaths (approx 30 axons to 1 oligodendrocyte)

Question 4

Functions of Microglia

Answer 4

Phagocytosis and immune functions - activated by disease and injury, amoeboid shape.

Question 5

Function of Schwann Cells

Answer 5

Myelination in PNS - 1:1

Also non myelinating

Question 6

Describe the lineage of neurones, astrocytes and oligodendrocytes

Answer 6

Neural cells to radial glia. Radial glia to oligodendrocytes or neuronal precursor or astrocytes.
Astrocytes to oligodendrocytes or neuronal precursors.
Neuronal precursors to neurones.

Question 7

Explain the lineage of schwann cells

Answer 7

Neuronal precursor - schwann cell precursor - immature schwann cell to either a promyleinating SC and then a myelinating SC or to a non myelinating SC. Depends whether it comes into contact with a neurone or not.

Question 8

Explain the lineage of microglia

Answer 8

derived from macrophages, enter CNS via meninges and then are quiescent until activated by damage or disease.

Question 9

Do glia have receptors

Answer 9

yes - very similar to those on neurones. Have receptors for the NTs released by close neurones. Specific types of receptor depends in glial cell type, location and maturity. Activation of the receptors results in changes in concentration of intracellular calcium.

Question 10

How do astrocytes regulate ions and water?

Answer 10

CO2 - take up by astrocytes, combind with water to carbonic acid, dissociated to bicarbonate and hydrogen ions. H+ then go to BV to regulate pH

K+ - high permeability to K+…large network so can allow K+ to be redistributed.

H2O follows ions osmotically into glia - AQP4 high density. Glia can distend/change shaped depending on demands.

Question 11

How is glutamate recycled?

Answer 11

80% is taken up into astrocytes where it is converted to glutamine by glutamine synthase. Then released back to the presynaptic neurone.

20% taken up into post synaptic cell

Question 12

What effects can calcium have in a cell?

Answer 12

Exocytosis, modulate ion channels, contraction, modulate intraceullar enzymes (and therefore metabolism) and regulate gene expression

Question 13

How is Ca++ signalling achieved between cells?

Answer 13

Gap junctions,,,ip3 and release Ca++ from stores
IP3…increase ca++ causes vesicles containing ATP to be released which acts on the next cell to increase IP3
or ATP can travel further away before causing IP3 release.

Question 14

Explain neuronal glia interactions

Answer 14

Astrocyte detectsNT release from axon. Doesn’t take it up but increases Ca++ intracellular and then releases glia transmitter to the presynaptic cell to increase or decrease NT release.

Question 15

Describe the neuronal lactate shuttle

Answer 15

Glut 1 allows glucose to be taken up by astrocytes. Converted to lactate and them transported back to the neurone for use as an energy source.

Question 16

what is a neurovascular unit?

Answer 16

Connects BVs and neurones

Astrocytes project towards microvessels via endfeet and define microdomains supporting the enclosed client neurone.

Question 17

How do glia regulate blood flow?

Answer 17

Glutamate is released, causes increase in Ca levels. Increased AA…increase P450…2HETE (vasoconstriction) and increase COX to produce PGs (vasodilation)