Neuropathy Flashcards
What are the layers of the meninges from deep to superficial?
- Pia
- Thin
- Arachnoid
- Spider-like
- Thin
- Dura
- Thick
Where are the astrocytes found and what is their function?
- Found in the central nervous system
- Functions
- Structural- create blood-brain barrier and supportive framework for neurons
- Insulates synapses
- Mildly phagocytic
- Metabolic functions
- Monitor and regulate interstitial fluid surrounding neurons
- Transmit information to each other
- Stimulate the formation of scar tissue
Where are the microglia found and what is their function?
- Phagocytes of the CNS- similar to macrophages
- Brain will recruit if infection present
- Smallest of the glial cells
- Cigar-shaped when reactive
Where are the oligodendrocytes found? What are their functions?
- Produce myelin in the CNS
- Surround few axonal processes
- Injury will cause demyelination
Where are the ependymal cells found? What is their function?
- Found in the CNS
- Cuboidal cells
- Line cavities and ventricals of CNS
- CSF production
- Barrier functions
- Give rise to epithelial layer that surrounds the choroid plexu
Where are the Schwann cells found and what is their function?
- Myelinate axons in the PNS
- Surround all axons of neurons in the PNS
- One schwann cell can myelinate many axons
- Wraps around a cell and squeeze out the cytoplasm so that all that is left is the myelin sheath
Where are the satelite cells found and what is their function?
- Support cells in the PNS, mainly in ganglia
- PNS equivalent of astrocytes
Why are neurons vulnerable to injury?
- They have a high metabolic rate
- They have little energy storage
- They have to take care of their axon
- The axon has no nissl substance
- Cannot make protein
- Cannot dispose of own waste
- The axon has no nissl substance
What is being pictured here? In what condition will this be seen?
- Chromatolysis of neuronal cells
- Cells get bigger
- Adaptive response to injury
- Does not usually resolve
- Seen in equine grass sickness
What is being depicted here? What can cause this condition?
- Neuronal wallarian degeneration
- Cells fall apart
- Breakdown of a nerve fibre distal to the point of injury (downstream to where the insult took place)
- Can occur with compression or stretching injury
- Creates axonal debris which has to be cleared by the myelo-macrophages to create a platform for healing
- Some regeneration can occur and may form a neuroma (mass of neurons- can be painful)
What is being depicted here? What may cause this condition?
- Neuronal vacuolation
- Cells become vacuolated
- Rare form of injury
- Common artefact in histology
- Seen with
- Transmissible spongiform encephalopathies
- Lysosomal storage diseases
- Early cell injury
- Some toxins
- Order of susceptibility (from most to least susceptible)
- Nerons, oligodendrocytes, astrocytes, microglia, blood vessels
What is being depicted here? What causes this disorder?
- Acute neuronal necrosis
- Usually a result of ischaema
- Non-ischaemic causes of neuronal necrosis
- Hypoxia
- Hypoglycaemia
- Nutritional deficiency
- Toxins
What are some causes of laminar cortical necrosis?
- Salt poisoning
- Water deprivation
- Lead and mercury toxicity
- Polioencephalomalacia in ruminants (cerebrocortical necrosis (CCN))Pathology unclear but is thought to be a thiamine deficiency or sulfide toxicity
- Thiamine is required for glucose metabolism
Describe neural cytoxic oedema.
- ATP deficit and failure of sodium pump where sodium and water build up within the cell (similar to hydropic degeneration)
- Intracellular
- Can occur as a result of hypoxia, ischaemia, and toxins
Describe the types of demyelination.
- Primary
- Myelin forms normally and then is selectively destroyed
- Caused by: toxicity, circulatory oedema, immune mediated, infectious cases, idiopathic, and hereditary, impaired maintenance, nutritional (copper, vitamin B12), toxins (cyanide)
- Secondary
- Loss of myelin following axonal damage (Wallerian degeneration, for example)
- The myelin is not able to be formed properly