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Flashcards in Nervous System Disorders Deck (54)
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What % of human genes are associated with the nervous system?



List 5 features specific to the CNS:

- protection of bony enclosures
- metabolic requirements
- absence of central lymphatics
- circulation of CSF
- distinctive patterns of wound healing


What is selective vulnerability?

functionally related neurons may be selectively damaged
Ex: exposure to limited hypoxia or hypoglycemia will cause greatest damage to portions of the hippocampus, pyramidal cells of the cortex, Purkinje cells of cerebellum, and the basal ganglia


Which part of the CNS is most affected by Alzheimer's disease?



Which part of the CNS is most affected by the effects of mercury?

Cerebellar granular neurons


Which part of the CNS is most affected by poliomyelitis?

Anterior horn cells


Is repair of the injured nerve processes better in the PNS or the CNS?



What are the 4 types of reactions of neuronal injury?

Acute neuronal injury (red neurons)
Axonal reaction (Central Chromatolysis)
Intra-neuronal deposits (inclusions)


Describe acute neuronal injury.

Can be caused by ischemia, infection, toxicity, etc
Includes loss of Nissl bodies, increased angularity, and nuclear pyknosis appear after 12-24 hours of irreversible injury
Fragmentation occurs


Describe the axonal reaction

Refers to reactions in the cell body that accompany axonal regeneration. Associated with synthesis of proteins & sprouting of axons.
Caused by axon trauma, hypoxia, etc.
Perikaryon swells and rounds up, Nissl disappears from the central cell body and nucleus moves to the periphery. With successful regeneration, the neuron recovers.


What is "Wallerian degeneration"?

the changes that occur in the distal axon (seen in the axonal reaction)


Describe neuronal atrophy.

common in chronic progressive degenerative disease & sometimes aging
- reduction in size, may (if severe) progress to neuronal death
- loss of a single neuron produces no reaction to glia, but can progress to selective loss of functionally related neurons (as in ALS) and reactive gliosis
- "trans-synaptic degeneration" of communicating neurons can occur


What are the 5 types of Intra-neuronal deposits?

- Neurofibrillary tangles
- Lewy bodies
- Viruses
- Lipofuscins
- Metabolic Storage Diseases (Tay-Sachs and Niemann-Picks)


Describe Neurofibrillary tangles and which type of conditions these are typical for

structures made of twisted cytoskeletal filaments, that contain ubiquitin (which tags abnormal proteins for removal). They are stained with silver
- typical in Alzheimer's disease, post encephalitic Parkinsonism, Parkinson-dementia complex of Guam, dementia of boxers


Describe Lewy bodies and which conditions these are typical for

Pink staining spheroids made of ubiquitin
- Idiopathic Parkinson's disease (substantia nigra) and Lewy-body dementia (cortex)


Describe Intracellular "inclusion bodies" (virus particles) and which types of conditions they are typical for

These appear in infected cells as in polio and viral encephalitis.
In rabies, known as Negri bodies


Describe Lipofuscins

They are the "wear and tear" pigments that accumulate within neurons from old age and chronic hypoxia


Describe metabolic storage diseases.

Contribute to accumulated intraneuronal deposits of complex lipids.
In retina, degeneration can lead to a cherry red spot in the fovea


Does death of a neuron or loss of an axon lead to myelin degeneration?



Does myelin loss lead to neuronal degeneration?

Not necessarily. Only if the condition is extensive or prolonged (chronic demyelinating disease)


Are glia more or less sensitive to injury than neurons?



What are the most sensitive to injury type of glia?

Oligodendrocytes- swell when stressed


What are the least sensitive to injury type of glia?



What happens in diseases of oligodendrocytes?

Oligodendrocytes are responsible for the production of myelin and may wrap around several axons, therefore a disease of oligodendrocytes including MS (demyelinating disease) cause oligodendrocytes and myelin to be replaced by astrocytic scars.


What are the 3 potential causes for increased intracranial pressure?

- space occupying lesions
- edema & swelling
- hydrocephaly


What are the 2 types of edema & swelling in the CNS?

Vascular (vasogenic)
- Most common
- Increased vascular permeability

Cellular (cytotoxic)
- increased cell water indicates injury


Describe Hydrocephaly

The volume of CSF is increased and the ventricles are dilated- typically an increased intracranial pressure


What is hydrocephaly ex vacuo?

A type of hydrocephaly in which the ventricles are expanded secondary to atrophy of the brain, in which case the CSF pressure IS NOT increased.


What is the pathogenesis of hydrocephaly?

- an imbalance exists between the rates of production (choroid plexus) and absorption (arachnoid granulations)


What are the potential causes of hydrocephaly?

- Overproduction of CSF
- Decreased transport and/or absorption of CSF
- Obstructive/ non-communicating (CSF doesn't reach subarachnoid space)
- Communicating (CSF enters subarachnoid space, but circulation or absorption is blocked)