neurocytology 2 Flashcards
what is the precursor to CNS support cells
Neuroepithelium for OligoD, astrocytes and ependymal
macrophages for microglia
whats the significance of the ependymal cells not being bound by tight junctions?
Ependymal cells make cerebrospinal fluid. When cerebrospinal fluid is made, it needs to be able to enterthe canal and into the interstitial space. Ocludins junctions is a tight seal. a tight seal is no bueno here. you need things to be able to move
when do ependyal cells begin to have tigh junctions?
when it needs to line the choroid plexus.
cerebrospinal fluid is made by. what is ependymal cells job here?
the choroid plexus.
here the ependymal cells regulate transfer of material
what about astrocytes allows them to be studied in vitro?
theyh have an organelle called a glial filament made of GFAP protein. Antibodies against GFAP can be used to visualize astrocytes
what about astrocytes allows them to communicate
multiple astrocytes are linked by Gap junctions. this allows them to pass small ions back and forth.
astrocytes can form a barrier around two neurons that have formed and synapse to seclude them from any surrounding synapse
astrocyts can be stimulated by neurotransmitters to
change their permeability to ion channels
change their morphology
change their content of neurotrophic factors (keep neurons alive)
change their ability to take up neurotransmitters
astrocyts attached to capillaries under LM
what role do the astrocytes play in the formation of the BBB
astrocytes actuallydont form the BBB. it is the tight junctions on the endothelial cells of the capillaries that forms the BBB. what astrocytes do is release factors that promote the formation of the tight junctions on the endothelial cells
where on the neuron do oligodendrocytes begin meylinating? and end?
at the initial segment. it ends at the acon terminal
how does meylin form?
when oligoD sends porcesses which wrap around axons in a spiral manner
what makes up each wrapping?
dark lines- major dense lines
light lines- intraperiod lines.
what is the paranodalregion?
where signals are transmitted between the axon and the oligodendrocyte. loss of these signals may cause MS
what is the schwan cell to axon ratio in PNS compared to OligoD to axon ration in CNS
in the CNS there is one oligodendrocyte wrapping each axon
BUT in the PNS, one Scwhannn cell can surround many axons
in the PNS even the unmyelinated axons are protected by schwann cells wrapping is that the same for CNS?
No in the CNS there are some axons that are just unmyelinated and naked
the adherin proteins in the PNS is
Po
what are the levels of wrapping in PNS axons
endo
peri
endonuerium
PNS nerve bundle
how many internodes are in PNS conpared to CNS
in PNS Schwann cells form 1 internode
in CNS oligoD forms many internodes
what is the layers of covers of an axon in the PNS?
schwann cells
basal lamina
connective tissue (edo,peri,epi)
what is the proces of regeneration in the PNS?
if the cell body is in tact, then the schwann cells can line up on the basal lamina, secrete grow factors to form processes that encourage the sprouting process to grow down the tubes
