neuroglia Flashcards
what are two main points about neuroglia
are not passive
just as important of not more so than neurons
why are neuroglia so important
many neurodegenerative diseases involve neurons and neuroglia and when they function incorrectly it can cause a number of problems
what are the three basic types of neuroglia
astrocytes
microglia
oligodendrocytes/ schwann cells
what are the two different terms for astrocytes
in grey matter- protoplasmic
white matter-fibrous
what do astrocytes contain
gap junctions(connexins) between them and specialised bundles of intermediate filaments
why do astrocytes have gap junctions
so they can propagate their own signals
what do specialised intermediate bundles within astroocytes contain
specialised proteins which can act as markers for these cells
what is the main function of astrocytes
separate nerve cells and oligodendrocytes so maintain integrity of NS
describe astrocytes ‘end feet’
cover most of free space on neuronal synapses and dendrites, capillaries and oligodendroyctes and they form cuffs around nodes of ranvier
what are three examples of molecules that astrocytes act as a buffer against
extracellular K
other ions
pH fluctuations
how do astrocytes affect the CNS
detoxify and provide homeostasis
what do astrocytes produce
cytokines and growth factors which can effect proliferations and survival of neurons
cell dhesion molecules which guide neuronal development
in the embryo what do astrocytes develop from
radial glial which span the brain parenchyma forming the framework for neural migration
describe astrocytes in adults
radial glial develop to form progenitors of astrocytes
what is the blood brain barrier
responsible for inducing and maintaining the tight junctions in the endothelial cells that form that barrier
where are microglia locates
in white and grey matter
what is the structure of microglia
have rod like somas and numerous processes do not seem to form networks like astrocytes
when are micrgolia activated
in diseases- proliferate and migrate to injury site
here they change morphology anf have thicket processes and larger cell bodies
what are the three functions of microphages
express MHC-1 and MHC-2
produce cytokines
act as macrophages
what are MHC 1 and MHC 2
antigen presenting cells to T cells
where are oligodendrocytes locates
CNs
white matter- cerebellar tracts
corpus collosum
also found in grey matter
what is the funciton of oligodendrocytes
can meylinate several axons
where are schwann cells located
PNS
what are 4 functions of schwann cells
myelination of neurons
separate neurons and isolate
in injury act as phagocytes
and secrete
what are three secretions of schwann cells
laminin
fibroconectin
collagen
all components of basal lamina and extracellular matrix
what is the main major function for both schwann cells and oligodendrocytes
produce myelin for saltatory conduction
when does myelination occur
late embryonic gestation and post-natal with CNS caudal to rostral and after PNS
describe the coverage of myelin
not continuous
nodes of ranvier
sheath divided into segments called internodes
what is myelin
specialised extension of cell membrane of myelinationg cells
describe the number of axons myelinated in oligodendrocytes and schwann cells
20-30 internodes
one schwann cell wraps around one axon
what bundles the nyelinated nerve in PNS
perinieum
what is a mesaxon process
forms a cup around the point of contact whose lips advance around axon until they meet
one then passes underneath other to become inner leaf which roates to form multiple layers
what is multiple sclorosis
immune mediated demyelinating disease
what is charcot marie tooth
demyelation of nerves of PNS
