glia Flashcards
what are functions of astrocytes
structural support, provide architecture, formation and regulation of blood brain barrier, metabolic support for neurones by providing energy substrates, regulation of extracellular ion concentrations and pH, removal of NTs from extracellular space
astrocytes maintain blood brain barrier as endfeet have receptors transporters and channels which regulate transport
they have NT receptors which help them remove NTs, they are main sink of NTs in brain
Astrocytes can release ATP and other substrates to regulate transmission
what are functions of oligodendrocytes
oligodendrocytes ensheath and myelinate axons
how do astrocytes develop?
radial glia form astrocytes during embryogenesis
the cortical precursors remain in
the cortex during development
what are different type of astrocytes?
fibrous astrocytes found in white matter of CNS, long processes with few branches
protoplasmic astrocytes found mainly in grey matter, lots of short highly branched processes
during development where are oligodendrocyte precursors?
they move away from ventricular zone of neural crest and populate the CNS
how do oligodendrocytes become mature?
when premyelinating processes of a premyelinating oligodendrocyte makes contact with an axon this stimulates differentiation.
Initiator processes then grow on receptive axons, most ensheath multiple axons within proximity to cell body
oligodendrocytes then undergo remodelling, non myelinating processes are lost and non compact myelin is formed around axon
during maturation oligodendrocyte sheath wrap interacts and fuse together to form compact myelin
what are the early precursors of glia and neurones during neurulation?
neuroepithelial cells develop into radial glia, this happens within ventricular zone of the neural crest. Neuroepithelial cells line ventricles during early stages of development throughout NS and later become radial glia.
what is the role of non myelinating schwann cells?
surround bundles of small diameter axons, they support and seperate unmyelinated axons
what neurones do schwann cells myelinate and where do they develop
they can myelinate axons which have a diameter larger than 1 micron, each schwann cell myelinates 1 axon.
SCs originate as neural crest cells
where do microglia originate? and what is their function
originate as macrophages outside CNS. They are brains immune system.
can exist in resting, activated and phagocytic states.
resting state has small cell body and many think branched motile processes. they scan a distinct territory and look for damage signals. damage signals cause transformation into active state, microglia processes move towards site of lesion.
In active state cell body size increases, processes are shorter, thicker and without branches, they move towards site of injury. Activation can happen from microglia, neurones or other glia. Active and resting states are reversible
in phagocytic state: only activated when signals of dead or dying neurones occur, this state is irreversible
