Neurology Response to Injury Flashcards
1
Q
“Neuro-”
A
lesion of peripheral nerves
2
Q
“Myello-”
A
Lesoin of spinal cord
3
Q
Leuko-
A
white matter
4
Q
Polio-
A
grey matter
5
Q
Leptomeninges
A
arachnoid and pia mater
6
Q
Pachymeninges
A
dura mater
7
Q
-malacia
A
degeneration, liquefaction, softening of neural tissues
8
Q
What are the normal layers of the meninges?
A
- Dura mater
- Subdural space
- Arachnoid mater
- Subarachnoid space
- Pia mater
9
Q
What is Grey Matter?
A
- Darker tissue of the brain and spnal cord
- Comprising nerve cell bodies and dendrites
10
Q
What is White Matter
A
- Paler tissue of the brain and spinal cord
- Composed mainly myelinated nerve fibers
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
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
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
14
Q
What is Neuropil?
A
- Eosinophilic fibrillar material between cell nuclei composed of the cell processes of neurons and glia
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
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
- Perivascular space is only distinct around larger vessels and is contiguous with the surface leptomeningies
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
What is a lysosomal storage disease?
* neurons have markedly expanded cytoplasm due to accumulation of ‘waste’ in lysosomes
* Most common in cats is ‘Globoid cell leukodystrophy’ “Krabbe's Disease”
26
What toxin causes lysosomal storage disease?
* Swainsonine (Locoweed toxicosis)
* Signs:
* Weight loss
* severe depression
* lethargy
* ataxia
* incoordination
* hypermetric gait
27
What causes Neuronal vacuolization?
* Spongiform encephalopathies
28
What is “Neuronophagia”
* Macrophages and other inflammatory cells surround (satellitosis) and phagocytose/digest dead neurons
29
What is Wallerian Degeneration?
* 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
What are the Axonal changes as a response to injury?
* Wallerian degeneration
* severing or direct axonal damage
* Regeneration
* PNS\>\>\>\>CNS
* Demyelination
* Primary - loss of Oligos or Schwann cells
* Secondary - death of the neuron
31
What are some causes of Primary demyelination?
* Canine Distemper Virus (CDV)
* Caprine Arthritis-Encephalitis Virus (CAE)
* Globoid cell leukodystrophy
32
What does Primary Demyelination look like grossly?
* Clear spaces in the cerebellar white matter
33
Where and why can CDV form inclusion bodies ?
* In the nucleus AND Cytoplasm
* Because its and RNA virus
34
What are the Astrocytes responses to injury?
* 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
What is the difference between an Astrocyte and a Fibroblast?
* 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
What are the synonyms for the formation of glial scars by astrocytes?
* hyperplasia of astrocytes
* astrocytosis
* astrogliosis
* focal gliosis
* glial nodule
* formation of “glial scars”
