L2 - Glial cells Flashcards
what is the difference between glial cells and neurones?
neurones are electrically excitable and generate APs
glial cells are not electrically excitable, they are homeostatic cells of the nervous system
why are glia not elecrically excitable?
few voltage gated channels
what types of glial cells are found in the CNS
macroglia
- astrocytes
- oligodendrocytes
- NG2 glia
microglia
what is the origin of macro glia? what are examples of macro glial cells (3)
neural origin (ectodermal) (neuroepithelium)
astrocytes
oligodendrocytes
NG2 glia
what is the origin of microglia
non neural origin , mesodermal
what types of glial cells are found in the PNS
schwann cells
enteric glia (GI tract)
satelite glial cells
olfactory ensheathing cells
what are satellite glial cells
glial cells of sensory and sympathetic ganglia
what different types of schwann cells are there?
non myelinating
myelinating
perisynaptic
describe some properties of astrocytes
long branching star-like processes contain GFAP (glial fibrillary acidic protein)
where do astrocyte processes contact
nodes of ranvier
what are the two main types of true astrocyte
fibrous astrocytes
protoplasmic astrocytes
where are protoplasmic astrocytes found
grey matter
where are fibrous astrocytes found
white matter
fucntions of astrocytes
structural support
form surface under the pia (glia limitans)
form signalling and transport pathway between neurones and blood vessels
inhibit regeneration in CNS
enwrap BBB
encase dendrites of CNS neurones
NT uptake
how do astrocytes provide structural support
their expression of intermediate filaments
how do astrocytes form signalling and transport pathway between neurones and blood vessels
there is an astrocyte between every brain capillary and neurone
describe organisation of astrocyte-neuronal network
a single astrocyte will contact multiple dendrites of one neurone
each neurone has multiple astrocytes that its in contact with
astrocytes do not overlap
how many axons can an oligodendrocyte myelinate
up to 30-50
function of oligodendrocytes
wrap around axons forming myelin sheaths
what are NG2 glia?
group of cells of the CNS that express neurone antigen 2
where do NG2 glia originate from
oligodendrocyte precursor cells
fucntions of NG2 glia
- form numerous contacts with neurones and receive functional afferents, forming functional synapses
- Able to generate oligodendrocytes during CNS remodelling and following demyelination (serve as multi potent neural stem cells)
function of CNS microglia
immunocompetent cells that form brain immune system activated by injury / disease
what are the three types of CNS microglia
resting
activated
phagocytic
what are schwann cells,
a type of microglia found in PNS
have a role in repair