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Systemic Pathology > Neurology Response to Injury > Flashcards

Neurology Response to Injury Flashcards

1
Q

“Neuro-”

A

lesion of peripheral nerves

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2
Q

“Myello-”

A

Lesoin of spinal cord

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3
Q

Leuko-

A

white matter

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4
Q

Polio-

A

grey matter

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5
Q

Leptomeninges

A

arachnoid and pia mater

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6
Q

Pachymeninges

A

dura mater

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7
Q

-malacia

A

degeneration, liquefaction, softening of neural tissues

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8
Q

What are the normal layers of the meninges?

A
  1. Dura mater
  2. Subdural space
  3. Arachnoid mater
  4. Subarachnoid space
  5. Pia mater
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9
Q

What is Grey Matter?

A
  • Darker tissue of the brain and spnal cord
  • Comprising nerve cell bodies and dendrites
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10
Q

What is White Matter

A
  • Paler tissue of the brain and spinal cord
  • Composed mainly myelinated nerve fibers
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11
Q

What are the different functions of the 4 types of neural cells?

A
  • Neurons - nervous function
  • Astrocytes - structure, BBB, immune response
  • Oligodendrocytes - myelin
  • Microglial - resident immune/phagocytic cells
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12
Q

What is the structure of Neurons?

A
  • Pyramidal to rhomboidal shaped
  • Large nucleus with prominent nucleolus
  • Cytoplasm contains Nissl substance (rER)
  • Axon - axoplasm, few organelles, myelinated
  • Myelin - Oligodendrocytes or Schwann cells
  • Cannot regenerate
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13
Q

Where were the different types of neural cells derived from?

A
  • Neuron - neural crest
  • Astrocytes - neural crest
  • Oligodendroglia - neural crest
  • Microglia - Bone marrow- derived monocytes
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14
Q

What is Neuropil?

A
  • Eosinophilic fibrillar material between cell nuclei composed of the cell processes of neurons and glia
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15
Q

What are the functions of astrocytes?

A
  • Structure - assist to maintain brain structure
    • mesenchymal cells of the CNS
  • Homeostasis - intracellular link between capillaries and brain cells (BBB)
  • Immune regulation - produce cytokines & chemokines, T-cell activation, microglial cell activation
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16
Q

What are the functions of Oligodendrocytes?

A
  • Make and maintain myelin
  • Myelinate many axons
17
Q

What is the function of schwann cells?

A
  • Provide myelin for peripheral nerves
  • One schwann cell myelinates a portion of one axon
18
Q

What is the function of Microglial cells?

A
  • Resident phagocytic cell
  • Analogous to Kupffer cells (Liver), alveolar macrophages (lung) and Langerhans cells (epidermis)
19
Q

What does the Microciculation of the brain look like?

A
  • Capillaries
    • Endothelial cells are connected by tight junctions
    • Small capillaries lack a pericapillary space
    • Astrocytic processes form the BBB
  • Larger Blood Vessels
    • Perivascular space is only distinct around larger vessels and is contiguous with the surface leptomeningies
      • “Virchow-Robbins Space”
    • Inflammatory cells in this space are called perivascular cuffs
20
Q

What is the neural cell response to injury?

A
  • Very small energy stores - depend heavily on intact blood supply
  • Virtually no capacity to regenerate
    • CNS nerve fibers cut = paralysis
    • PNS = possible regeneration
      • Healing through astrocytes NOT fibrosis
  • Very little resistance to even relatively non-pathogenic organisms
    • No lymphatics, lymphoid tissue
21
Q

What is Reversible cell injury?

A
  • Results in dispersion of Nissl substance (rER) and cell welling
  • Loss of obvious Nissl substance = “chromatolysis”
22
Q

What happens to ischemic neurons?

A
  • Shrunken, red, angular, pyknotic nuclei
  • Neurons are MOST susceptible to ischemic injury
23
Q

What causes dead neurons?

A
  • Necrosis:
    • Ischemia
    • Viral infections (some cause inclusions)
    • TOxins
    • Prions - large cytoplasmic vacuoles
    • Metabolic disease - lysosomal storage disease
  • Apoptosis:
    • Inherited disease/congenital defects
    • Viral infections
    • Toxins
24
Q

What causes intranuclear inclusion bodies?

A
  • Herpes Virus
  • Adenovirus
  • Posvirus
  • Rabies - “Negri bodies”
25
Q

What is a lysosomal storage disease?

A
  • neurons have markedly expanded cytoplasm due to accumulation of ‘waste’ in lysosomes
  • Most common in cats is ‘Globoid cell leukodystrophy’ “Krabbe’s Disease”
26
Q

What toxin causes lysosomal storage disease?

A
  • Swainsonine (Locoweed toxicosis)
  • Signs:
    • Weight loss
    • severe depression
    • lethargy
    • ataxia
    • incoordination
    • hypermetric gait
27
Q

What causes Neuronal vacuolization?

A
  • Spongiform encephalopathies
28
Q

What is “Neuronophagia”

A
  • Macrophages and other inflammatory cells surround (satellitosis) and phagocytose/digest dead neurons
29
Q

What is Wallerian Degeneration?

A
  • Spinal cord compression resulting in axonal degeneration
    • Macrophages infiltrate and phagocytize axonal debris and degenerated myelin - hallmark
  • Long term effects depend on:
    • Severity of injury
    • Intact or damaged endoneural tube surrounding axon
    • Integrity of oligodendroglia
30
Q

What are the Axonal changes as a response to injury?

A
  • Wallerian degeneration
    • severing or direct axonal damage
  • Regeneration
    • PNS>>>>CNS
  • Demyelination
    • Primary - loss of Oligos or Schwann cells
    • Secondary - death of the neuron
31
Q

What are some causes of Primary demyelination?

A
  • Canine Distemper Virus (CDV)
  • Caprine Arthritis-Encephalitis Virus (CAE)
  • Globoid cell leukodystrophy
32
Q

What does Primary Demyelination look like grossly?

A
  • Clear spaces in the cerebellar white matter
33
Q

Where and why can CDV form inclusion bodies ?

A
  • In the nucleus AND Cytoplasm
  • Because its and RNA virus
34
Q

What are the Astrocytes responses to injury?

A
  • Cell Death:
    • Necrosis - not as susceptible to ischemic injury as neurons
    • Apoptosis
  • Nonlethal reactions - function to fill in or wall off areas of necrosis
    • small area = proliferation & “glial scar” (focal gliosis)
    • Large area = cavitation in brain tissue (Lacunar infarcts)
35
Q

What is the difference between an Astrocyte and a Fibroblast?

A
  • Astrocytes:
    • Mesenchymal cell of CNS
    • Maintain structure
    • Maintain BBB
    • Cannot produce fibrosis in the neuropil
    • Lay down collagen only in meninges
  • Fibroblasts:
    • Mesenchymal cell in body
    • Maintain structure
    • Lay down collagen as part of healing
36
Q

What are the synonyms for the formation of glial scars by astrocytes?

A
  • hyperplasia of astrocytes
  • astrocytosis
  • astrogliosis
  • focal gliosis
  • glial nodule
  • formation of “glial scars”

Systemic Pathology (19 decks)

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