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45 Cards in this Set
- Front
- Back
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What happenes when there is acute ischemic or hypoxic damage to the cell body of a neuron?
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This produces shrinkage of the cell body and a hypereosinophilia.
The nucleus becomes pyknotic. These are thought to be irreversible and lethal changes |
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What causes cell body atrophy of neurons?
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Atrophy is the hallmark of many neurodegenerative disorders (eg Alzheimer, Parkinson, and Huntington diseases). The neuron may be involved directly or indirectly, through retrograde (via efferents) or anterograde (via afferents) transneuronal or transsynaptic degeneration
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What is cell body atrophy of neurons?
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A non-eosinophilic shrinkage of the cell body
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What causes chromatolysis of neuron cell bodies?
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Chromatolysis results from axon damage (including axon transection). The cell body becomes hypertrophic and loses its Nissl substance (rough ER). Chromatolysis may be followed by regrowth of the axon from the point of damage, a phenomenon more often seen in the peripheral than in the CNS.
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What occurs in neuronal storage diseases?
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Excessive amounts of lipids, carbohydrates, glycosaminoglycans, or glycoproteins accumulate within neurons, enlarging and distorting the normal geometry of the cell body and proximal processes.
These are usually seen in the context of inherited disorders of lipid or glycosaminoglycan catabolism (eg Tay Sachs disease, mucopolysaccharidoses). In may of these diseases, similar storage material accumulates in glial cells |
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What do inclusions represent?
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Abnormal nuclear or cytoplasmic structures.
Some reflect the focal storage of metabolites, some the presence of viral proteins or nucleoproteins and some the abnormal accumulation of structural proteins (eg neurofibrillary tangles, Lewy bodies) |
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What is lipofuscin?
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An insoluble mix of proteins, lipids, and minerals that accumulates in neurons and astrocytes during the normal aging process
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What is neuronophagia?
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The phagocytosis of degenerating neurons, usually by macrophages. This is commonly seen after hypoxic or ischemic insults or during viral infections
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What is Wallerian degeneration?
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The loss of the axon (and its myelin sheath) distal to the point of axonal damage
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What is "dying back degeneration"?
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A degeneration of the most distal axon, followed by the progressive loss of more and more proximal regions, is often seen in toxic peripheral neuropathies.
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What is demyelination?
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Demyelination refers to the primary loss of myelin with relative preservation of the axon (eg as in MS)
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What is a spheroid?
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A focal enlargement of an axon due to damage, regardless of cause: trrauma, local areas of necrosis, or toxic-metabolic insults. Spheroids contain mixtures of lysosomes, mitochondria, neurofilamants, and other cytoplasmic constituents. Slowing or cessation of axoplasmic transport at sites of damage presumably account for spheroids
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What is dendrite hypoplasia?
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It refers to an inadequate development of dendritic branches. This is seen in many types of mental retardation, including congenital hypothyroidism (cretinism)
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What is dendrite atrophy?
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A reduction in the volume and surface area of dendritic branches, commonly seen in neurodegenerative diseases.
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What are neuritic plaques?
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Collections of degenerating axons and dendrites, mixed with microglia and astrocytes and associated with the extracellular deposition of amyloid (beta-amyloid)
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What does status spongiosis refer to?
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A spongy state of the neutrophil, the formation of fine to medium sized vacuoles representing swollen neuronal and astrocytic processes. This change is typical of transmissible spongiform encephalopathies, such as Creutzfeldt-Jacob disease
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Where are astrocytes located? What do they do?
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-All regions of the brain
-Contact blood vessels, pial surfaces, and enfold synapses in their functions to maintain the concentration of ions, neurotransmitters, and other metabolites within normal levels in the extracelullar space -Play a fundamental role in inducing BBB functions in cerebral vessels |
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How do astrocytes respond to pathological processes, such as hypoxic-ischemic damage or trauma?
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Hypertrophy (enlargement)
Hyperplasia (proliferation) |
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Describe the response of astrocytes to pathologic processes
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Astrocytes form the majority of CNS scars (unlike other organs, in which scars are typically collagenous, formed by fibroblasts)
Astrocytes develop abundant pink cytoplasm, either due to imbibing plasma proteins and fluid in short-term (when the BBB is broke) or filling up with intermediate filaments (in long-term scaring), The descriptive term reactive, hypertrophic or gemistocytic is often used to describe this change. |
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Describe Alzheimer type II astrocytes
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They display a swollen, lucent nucleus and swollen cytoplasm, and are found in gray matter in patients with chronic or acute liver disease.
They are thought to be related to the hyperammonemia of hepatic failure |
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What are Rosenthal fibers?
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Eosinophilic, refractile inclusions composed of intermediate filaments and small heat shock proteins, found in low grade, pilocytic type of astrocytomas, Alexander's disease (a rare leukodystrophy) and occasionally in old scars.
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What are Corpora amylacea?
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Spherical accumulations of polyglucosan (branched-chain glucose polymers), which increase in numbers with age, particularly in a subventricular and subpial locations, and in glial scars.
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When do viral inclusions occur?
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With cytomegalovirus
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What do astrocytomas represent?
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A common form of brain tumor
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What do astrocytes do after damage to the CNS?
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They become phagocytic
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What are oligodendrocytes?
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The myelinating cells of the CNS
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Describe what happens after demyelination of oligodendrocytes
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Oligodendrocytes or progenitors of oligodendrocytes are able to remyelinate demyelinated axons, and thus help to repair demyelinated lesions.
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Describe myelin edema
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In certain toxic and metabolic settings, fluid accumulates within myelin sheaths, leading to intramyelinic edema
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When does cell loss of oligodendrocytes occur?
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It occurs in a variety of disorders, including immune mediated (MS), viral (papova virus of progressive multifocal leukoencephalopathy), and toxic (e.g. psychosine).
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When do changes in the vessel wall occur?
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They accompany a large number of disorders (eg fibrotic and hyalin thickening in hypertension, radiation damage, and atherosclerosis)
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When do you see endothelial cell loss?
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In radiation damage, ischemia, lead, rickettsiae and viruses
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What are Schwann cells?
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The myelinating cells of the peripheral nervous system. (good regenerative potential; loss of myelin sheath accompanies loss of Schwann cell or axon)
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When are Schwann cells lost?
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In demyelinating peripheral neuropathies.
In certain toxic (eg lead) and infectious (eg leprosy) peripheral neuropathies |
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What can non-myelinating Schwann cells do?
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They are able to remyelinate demyelinated internodes
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Describe schwannomas
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Common, usually benign, neoplasms of peripheral nerves
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When do viral inclusions form in oligodendrocytes?
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In progrssive multifocal leukoencephalopathy
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Comment on oligodendrogliomas
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A common primary CNS neoplasm
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Where are ependymal cells
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Ependyma line the ventricular surface
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Describe cell loss of ependymal cells
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Many noxious stimuli (e.g. increased intraventricular pressure, intraventricular blood, infectious organisms) can destroy ependyma with resultant loss of ependymal lining and proliferation of subependymal astrocytes (granular ependymitis)
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Describe the development of microglial cells
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Microglial cells are bone marrow derived and enter the CNS during embryonic development
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What happens to microglial cells in pathological cells?
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They become macrophages
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What is the most effective antigen-presenting cell in the CNS?
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Microglia
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What happens when you get lesions in which the BBB is disrupted?
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The lesions induce the transit of monocyte-macrophage cells from the circulation into the CNS to participate in phagocytic activity
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What is the major determinant of the BBB?
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Tight junctions between cerebral endothelial cells
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When do you see hypertrophy and hyperplasia on endothelial cells?
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Commonly seen in ischemia and in the vicinity of primary and metaplastic neoplasms
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