Basic Neuroanatomy Flashcards
macroglia
astrocytes, oligodendrocytes, and ependymal cells
glial cells
classified as macroglia and microglia
provide support and protection for neurons
outnumber neurons 10 to 1 in the central nervous system
astrocytes
largest glial cell
astrocyte support functions
regulates interstitial fluid
modulates signals that regulate blood flow in response to neuronal activity
provides structural support; astrocytes are essential components of the blood brain barrier and of glial-limiting membranes (aka glial limitans) that line the pia mater and parenchymal vasculature
provides nutritional support via glycogen storage
protects against the death of neurons by activating antioxidant pathways
astrocyte enzyme
glutamate synthase
glutamate synthase
important for the removal of excess glutamate and GABA from synapses
also plays a role in the detoxification of ammonia
astrocyte angiogenic factors
VEGF
VEGF
decreases the stability of the blood-brain barrier with inflammatory conditions and CNS tumors
immunohistochemical staining to identify astrocytes
stain for glial fibrillary acidic protein (GFAP)
glial fibrillary acid proteins (GFAP)
make up intracellular intermediate filaments located in astrocytic processes
reactive astrocytes
become reactive and hypertrophic from injury, infection, or chronic neurodegeneration
upregulate GFAP, proliferate, and form a glial scar that surrounds damaged CNS tissue
oligodendrocytes
responsible for the formation of myelin in the central nervous system
myelin
provides electrical insulation that allows for saltatory conduction, the speed of which is determined by the length of the internodal myelin segments. larger axonal diameters conduct faster than smaller diameters
identify myelinated fibers on microscope with
Luxol fast blue (LFB) staining
lack or paucity of LFB staining can suggest demyelinating disease
leukodystrophy and oligodendrocyte
typically involve metabolic and lysosomal pathways that are necessary for normal oligodendrocyte function
progressive multifocal leukoencephalopathy (PML) and oligodendrocytes
likely involves lytic infection of oligodendrocytes to induce demyelination
oligodendroglioma
primary brain tumors
classic ‘chicken wire’ appearance on histopathology and fried egg appearance
astrocyte-oligodendrocyte crosstalk
communication occurs by direct cell-cell gap junctions, as well as secreted signaling molecules
importance of astrocyte-oligodendrocyte communication is made apparent in primary astrocytopathies such as Alexander disease and osmotic demyelination syndrome
Alexander disease
rare leukodystrophy caused by mutations in GFAP gene resulting in accumulation of abnormal filaments (Rosenthal fibers) in astrocytes leading to oligodendrocyte death and demyelination
Infantile Alexander Disease
presents with megalencephaly, seizures, spasticity, and developmental delay
osmotic demyleination syndrome
astrocyte death is observed before oligodendrocyte death and demyelination
ependymal cells
produces and facilitates the movement of CSF
lines the ventricles and central canal of the spinal cord
resembles the cuboidal or columnar epithelium with some cilia and microvilli on histopathology
ependymal cells on histopathology
resembles the cuboidal and columnar epithelium with some cilia and microvilli
microglia
primary immune cell of the central nervous system
- responsible for antigen presentation
- activates in response to tissue damage and ischemic injury. once activated, becomes a motile, phagocytic cell (adept for neuronophagia) which forms reactive oxygen species and secretes cytokines and proteases
microglia derived from
smallest and rarest glial cell
derived from bone marrow/monocytes and enter the CNS in the perinatal period
- all other glial cells and neuronal cells are derived from neural tube cells
neuronal cells
responsible for receiving, integrating, and propagating information to other cells
parts of neuronal cells
dendrites
cell body
axons
dendrites
receive information from other neurons at synapses
changes in dendritic spines are critical for neural plasticity that occurs during development and learning