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University of Toronto Scarborough
Biological Sciences
Stefan Rusyniak

Astrocytes 5 main functions y Metabolically support neurons and blood vessels through transport of metaboliteswastes between them y Isolate neurons from blood vesselsby forming the pericascular feet and secreting glia limitan to form the BBB y Provide scaffolding for blood vessels and neural tissuerecall that there is very little connective tissue if any actually in neural tissue Something is required to hold everything in place and what does it is the network of cytoplasmic processes extending out from astrocyteso Also if damage occurs its not like solid is left behind Neural tissue undergoes liquifactic necrosis so if cell dies leaves empty space Therefore astrocytes provide a network to support neural tissuey Also guides development of axons and dendrites especially in early development o Inhibits the regrowth of axons in the CNS This is a precautionary mechanism because the CNS is ultimately the control centre for all aspects of the body Should the axon regrow and reattach to the wrong segment would have the stimulation of the wrong neuron bad mixed up signals As such astrocytes secrete substances to inhibit the regrowthy Regulate activity of microglial cellsmicroglial cells are essential phagocytic cells in the CNS like the macrophages of the CNS o Two types of astrocytesProtoplasmicfound mostly in gray matter Many short broad branched cellular processes Often have a mossy appearanceFibrousfound mostly in white matterLonger more slender processes Also fewer of them Microglial cells y Smallest neuroglial cell y Phagocytic cell that develops in the bone marrow and basically functions like a macropage in the CNSactually develops from the mononuclear phagocytic systemy Cant easily see on slides but key histological features are o Elongated small nucleus o Short spiny processes processes look like they have little spikesEpendymal cells y Found generally in central canal of spinal cord and ventricles in the brain of certain animcals y Look like a simple columnar covering on the central canal o Ependymal cells involved in the secretion of cerebrospinal fluid o Cells have cilia and microvilliCilia allows for the movement of the CSF through the central canalMicrovilli aids in the absorption of CSF Often in contact with astrocytes o Are NOT true epithelial cells because they have no basement membrane
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