Astrocytes and microglia

Protoplasmic and fibrous

2 types of astrocytes

Grey matter

Where are protoplasmic astrocytes found?

White matter

Where are fibrous astrocytes found?

Protoplasmic

Which type of astrocytes have multiple primary processes split into many small branches

Fibrous

Which type of astrocytes have long, unbranched primary processes organised along withe matter tracts ?

Support neurons

Astrocyte only exist to …

Glutamate

What receptor allows astrocytes to monitor activity of the CNS and remove NTs from the cleft and restore it for reuse

Glut-1

What transporter takes glucose across the blood-retinal barrier at the vascular endothelium and is also expressed in astrocytes?

Metabolise glycogen stores and produce lactate from glycolysis (exported to neurons to be converted to pryuvate for Krebs)

What astrocytes do in periods of low blood sugar/ high energy demand?

Low (only need glycolysis)

Oxygen-consumption of astrocytes is …

glutathione (GSH)

What antioxidant do astrocytes provide neurons?

‘Scavenges’ free radicals and acts as H+ donor for glutathione peroxidase

What does GSH do?

Tripartite synapse

Initimate structural association between astrocytes and each synapse

Glutamate, D-serine, GABA, ATP and adenosine

5 Neuromodulators used by astrocytes

Continuous vascular endothelial cells of the cerebral vasculature and their tight junctions

Where is the blood- brain barrier?

Secreted factors by astrocytes

What induces the BBB in development and maintains it in adulthood?

Glia limitans

Astrocyte foot processes form a continuous layer of … attached to the basement membranes of vessels

Neural plasticicty

The capacity of the brain to alter its structure, connections and function inn response to internal or external stimuli

Synaptic pruning

Removal of redundant synapses facilitated by astrocytes and microglia

Phosphatidyl serine

What do synapses destined for pruning display?

MERTK

Which receptor can bind directly to Phosphatidyl serine to induce phagocytosis by either astrocytes or microglia?

Binding and engulfment by astrocytes through the surface receptor MEGF10

If Phosphatidyl serine binds to the complement protein C1q in Extracellular space what does this induce?

Complemented cascade and release of C3b

What can C1q trigger downstream?

Binding by microglia-specific C3R and synapse is engulfed

What does the display of C3b lead to?

Astrogliosis

When astrocytes divide in response to brain injury

Primitive yolk sac

How are microglia derived?

Microglia

Self-sustaining population of cells that only divide and proliferate when necessary

To replenish dying microglia OR clonal expansion in response to damage/infection

When will microglia proliferate?

Inflammatory cytokines and chemokines

What do activated microglia release to alert the systemic immune response?

Immune surveillance

When microglia constantly sample the Extracellular environment for soluble molecules that indicate tissue damage

PAMPs / DAMPs

What do soluble molecules in the ECM display to indicate damage?

Toll-like receptors

How are PAMPs and DAMPs detected?

9

How many TLRs do microglia express?

Unmethylated prokaryotic DNA or cell wall components

What are PAMPs released by?

Chromain, ribosomal proteins, lysosomal ennzymes or mitochondrial components in the Extracellular space (not normally present here)

What are DAMPs released by?

Specialised microglia with direct access to the vascular basement membrane

What are juxtavascular microglia?

At the glia limitans

Where are the juxtavascular microglia located?

Efferocyctosis

Phagocytise removal of dead cells from tissue environments

Prenatal development and childhood, after trauma or stroke

When does efferocytosis occur in the brain?

Phosphatidyl serine

What is flipped to the outside of the lipid bilayer in the early stages of apoptosis?