Flashcards in 6. Neuropathology Deck (82)
what do astrocytes do?
respond to almost any stiumlus, first by enlarging and then by retracting.
what type of cell mends an injured area?
cell processes of fibrous astrocytes form a network - glial scar or gliosis
what are Alzheimer's Type II glia?
astrocytes proliferate, undergo an alteration in conditions in which blood and CSF ammonia levels are elevated. ex: hepatic encephalopathy, or with elevated serum electrolytes
what do oligodendrocytes do?
form and maintain central myelin,
what will the destruction of oligodentrocytes lead to?
demyelination as in progressive multifocal leukoencephalopathy (PML) which is a viral condition.
ependymal and choroid plexus cells: what is their origin?
what do ependymal cells do?
line ventricles, maintain equilibrium between cerebrospinal and interstitial fluids of the brain.
what do ependymal cells look like?
tall columnar ciliated cells, show variation in cell config depending on location/function.
what is the response of ependymal cells and choroid plexus to an insult?
to die. they are not helpful.
when do ependymal cells or choroid plexus cells become of interest?
if they disappear or become neoplastic
what do microglial cells do?
not glial cells. specialized monocyte/macrophage which arises in the bone marrow, and populates the CNS pre birth. assist in remodeling of fetal CNS by phagocytizing cells that die.
what do microglial cells look like?
small, dense, elongated nuclei, no identifiable cytoplasm except with special stain.
how do microglia arrange themselves?
thin branches of cytoplasm radiating from nuclear zone, establish non-overlapping territories
what are the functions that microglia can carry out?
-can become macrophages
-can be immunocompetent cells, presenting antigen and secreting cytokines
-can proliferate and assume phenytope of macrophages when there is neuronal death due to tumor.
-if there is neuronal death by virus, microglial stars/nodules form
schwann cells do what?
similar functions to astrocytes, oligodendrocytes, and microglia in the PNS.
what can schwann cells do to motor and sensory axons?
ensheathe to increase conduction velocities
describe Selective Vulnerability. example?
some regions of the brain are more affected than others by insult or injury. ex: cells of hippocampus show ischemic/anoxic changes much earlier than other regions of the brain.
what is released in presynaptic terminals during anoxia?
how does glutamate in the presynaptic terminals cause toxicity?
impaired cellular uptake, concentration of glutamate rises to toxic levels by binding to NMDA receptors, opening up Na and Ca channels, causing osmotic swelling due to Na entry, neuronal death due to entry of Ca.
deficiency of Vit B1 causes what?
B1 = thiamine. causes Wernicke's encephalopathy. destruction seen in mammillary bodies, wall of third vent and floor of 4th vent.
deficiency of Vit B12 causes what?
destruction of the white matter in the dorsal and lateral columns of spinal cord
Vasogenic edema is what?
BBB is compromised, allowing some fluid to escape from intravascular space to intercellular space/brain parenchyma
cytotoxic edema is what?
glia or neurons enlarge due to changes in cell membranes. seen with hypoxia/ischemia
how is raised Intracranial Pressure defined?
as more than 200 mmH2O with patient recumbent
what are herniations?
movement of soft neural tissues across or against other firmer tissue (falx, tentorium)
what causes herniations?
mass effect, raised ICP.
what is hydrocephalus?
excess accumulation of CSF in the ventricular system.
what causes most hydrocephalus?
decr flow through ventricular system, impaired resorption of CSF. rarely, incr production of CSF (choroid plexus tumors)
in the CNS, an infarction turns into what kind of tissue?
pus/liquid rather than scarring as in the rest of the body