Astrocytes in the guise of glia limitans form the pial cover of the CNS, control blood-brain barrier and act as chemosensors, thus contributing to systemic homeostasis (regulation of energy balance, blood pH and Na + concentration).
The vascular endfeet, which plaster along the entire vasculature, release vasoactive substances thus contributing to functional hyperemia. Astrocytes define the cytoarchitecture of the grey matter by tiling the latter and by forming contacts with the vasculature by vascular endfeet and by glial sheets at all surfaces of the brain. Astrocytes regulate metabolic homeostasis through synthesizing glycogen and supplying neurons with energy substrates. Astrocytes sustain neurotransmission by supplying neurons with neurotransmitter precursors and control cellular homeostasis through embryonic neurogenesis (that occurs from radial glia) and adult neurogenesis (which involves stem astrocytes of neurogenic niches). Astrocytes maintain molecular homeostasis of the CNS by transporting major ions and protons, by removing and catabolizing neurotransmitters, and by releasing neurotransmitter precursors and scavengers of reactive oxygen species. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ. Astrocytes are highly heterogeneous in form and function and demonstrate remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astroglia are a class of neural cells (also known as astrocytes) of ectodermal, neuroepithelial origin that sustain homeostasis and provide for defense of the central nervous system (CNS) ( FIGURE 1).
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