Neurological Cell Types, Response to Injury

What are many brain lesions have clinical signs from?

Space occupying/pressure lesions like abscess, edema, hydrocephalus, hemorrhage, tumors

T/F BBB prevents certain drugs, chemicals, nutrients, antibodies from entering brain?

True

Why is there not much resistant to non-pathogenic organisms in the CNS?

There is no lymphoid tissue or lymphatics

What is chromatolysis?

The loss of Nissl substance

What does reversible injury look like?

Swelling and chromatolysis

What does irreversible damage look like?

Shrunken and hypereosinophilic

What are red neurnons?

Dead

What do ischemic neurons look like?

Red, shrunken, angular, pyknotic nuclei

What is the most susceptible cell to ischemic injury in the CNS?

Neurons

What can cause neurons to die and become necrotic?

Ischemia
Viral infections
Toxins
Prions
Metabolic diseases (lysosomal storage disease)

What can cause neurons to die and apoptose?

Inherited disease
Viral infections
Toxins

Describe acquired lysosomal storage diseases

Caused by toxins like Swainsona, Sida, Turbina, Atragalus, Oxytropis, Ipomea, and inhibits a-mannosidase (resembles mannosidosis)

What are the signs of an acquired lysosomal storage disease?

Usually i herbivores that eat toxic plants and causes weight loss, depression, lethargy, ataxia, incoordination, hypermetric gait

What is neuronophagia?

Macrophages and other inflammatory cells surround and phagocytose dead neurons

What is Wallerian Degeneration?

Spinal cord compression causing axonal degeneration

What do the long term effects of Wallerian Degeneration depend on?

Severity of injury

Intact or damaged endoneural tube surrounding axon

Integrity of oligodendroglia

What are common axonal changes?

Wallerian degeneration

Regeneration

Demyelination

Where is regeneration best in the nervous system?

PNS

What is primary demylination?

Loss of oligos or Schwann cells by canine distemper virus, caprine arthritis-encephalitis virus, or globoid cell leukodystrophy

What is secondary demyelination?

Caused by death of the neuron

What is the response to severed, direct trauma/crushing, or stretching/overextension in an axon?

Wallerian Degeneration

What happens if the basal lamina of the neuronal tube is still intact after injury?

Rate of successful regeneration is much more likely

What is a hallmark of Wallerian degeneration?

Macrophages infiltrate and phagocytize axonal debris and degenerated myelin

What do intranuclear inclusion bodies usually mean

DNA virus

What cell type is very resistant to ischemic injury and necrosis?

Astrocytes

What do astrocytes do during nonlethal reactions?

Fill in or wall off areas of necrosis

What is a glial scar?

Astrocytes proliferate in a small area of necrosis

What is a lacunar infarct?

There is a large area of necrosis and the astrocytes attempt to wall off the necrotic area resulting in areas of cavitation

Describe astrocytes

Cannot produce fibrosis in the neuropil

Lay down collagen ONLY in the meninges

Maintain structure

Mesenchymal cell of CNS

Maintain BBB

How can oligodendroglia react to injury?

Necrosis or apoptosis

Demyelination

Hyperplasia to remyelinate a demyelinated axon

Where do CNS macrophages come from?

Resident microglia and peripheral blood monocytes

What are the least susceptible of all neural cells to ischemic injury?

Microglia

What are the 2 CNS vascular disturbances?

Hypoxia/ischemia

Cerebral edema

Where does the CNS get its blood supply?

Carotid and basilar arteries

What is the circle of willis?

Joining of the carotid and basilar arteries at the base of the brain around the pituitary

T/F the circle of willis provides vascular redundancy?

True

What matter type is more susceptible to hypoxia?

Gray matter

What neurons are the most susceptible to hypoxia?

Cerebral cortical neurons

What neurons in the CNS are less susceptible to ischemia?

Spinal cord and brain stem

Rank the common cells and their susceptibility to hypoxia?

Neurons

Oligodendrocytes

Astrocytes

Microglia

What are some possible causes of hypoxia?

Anesthesia accident

Dystocia

Umbilical cord flow impairment

Carotid obstruction

What is infarction?

Complete and total vascular occlusion

T/F infarction is one of the causes of stroke?

true

What are some causes of infarction?

Intracerebral hemorrhage

Histophilus somni

Spticemic, bacterial emboli

Fibrocartilaginous emboli in the spinal cord

Feline ischemic encephalopathy

Vascular accidents

T/F cerebral infarcts are much less common in domestic animals because hypertension and atherosclerosis is less common?

True

Describe acute CNS infarcts

Swollen

Hemorrhagic

Irregular in shape

Describe chronic CNS infarcts

Necrotic tissue removed by macrophages

Small infarcts become foci of gliosis

Large infarcts become cavities

What is the pathogenesis of acute hemorrhagic infarcts?

Direct trauma

Mechanical disruption of blood vessels

Hemorrhage

Place of hit or synergy on the opposite side

What is the pathogenesis of Histophilus somni causing an acute hemorrhagic infarct?

1. H. somni septicemia

2. Biofilm in CNS vasculature

3. Necrotizing and suppurative vasculitis

4. Thrombosis

5. Hemorrhagic infarcts with bacteria

6. CNS infarcts

What does fibrocartilaginous emboli in the spinal cord cause?

Complete and total vascular occlusion and infarction

What animals are more likely to get fibrocartilaginous emboli in the spinal cord?

Dogs (large breeds) and pigs

What does a tumor emboli cause?

Hemorrhagic and necrotic infarcts

What does -malacia mean?

Degeneration, liquefaction, softening of CNS tissues

What species do not have gyri?

Mice, avian, reptiles

What part of the brain should you collect?

All of it

What is gray matter made of in the brain?

Cell bodies and dendrites

What is white matter made of in the brain?

Myelinated axons

What supports the grey and white matter in the brain?

Glial cells and vasculature

What are the layers of the CNS?

Dura mater

Subdural space

Arachnoid matter

Subarachnoid space (CSF)

Pia mater

What are pachymeninges located?

Dura mater

Where are leptomeninges located?

Pia and arachnoid mater

What do neurons do?

Nervous function

What do astrocytes do?

Structure, BBB, immune response

What do oligodendrocytes do?

Myelin

What do microglial cells do?

Resident immune/phagocytic cells

What is in the cytoplasm of neurons?

Nissl Substance

What cells are derived from the neural crest?

Neurons, astrocytes, and oligodendroglia

Adrenal gland, tissues of the head, melanocytes

What cells are bone marrow-derived?

Microglia

What is neuropil?

Fibrillar material between cell nuclei made of cell processes of neurons and glia

How do astrocytes support the structure of the CNS?

Maintain brain structure. Mesenchymal cell of the CNS

How do astrocytes contribute to homeostasis?

Intracellular link between capillaries and brain cells also form glia limitans

How do astrocytes contribute to immune function?

Produce cytokines and chemokines, T-cell activation, microglial cell activation

What is the function of oligodendroglia?

Make and maintain myelin in the CNS

Myelinate many axons

What do Schwann cells do?

Provide myelin for peripheral nerves

One Schwann cell myelinates a portion of ONE axon

What are the smallest glial cells in the brain?

Microglial

What are microglial cells analogous to?

Kupffer cells, alveolar macrophages, and langerhans cells because they are all also resident phagocytic cells

How are endothelial cells connected?

Tight junctions

T/F small capillaries lack a pericapillary space?

True

What is the perivascular space contiguous with in larger blood vessels?

Leptomeninges

What is the Virchow-Robbins space?

Perivascular space in larger blood vessels

What are the inflammatory cells in the perivascular space?

Perivascular cuffs

Why do neurons depend heavily on intact blood supply?

They have very small energy stores

T/F neurons have virtually no capacity to regenerate?

True

What happens if nerve fibers are cut in the CNS?

No regeneration

What happens if nerve fibers are cut in the PNS?

Regeneration can occur

How is healing in the CNS done?

Through astrocytes NOT fibrosis

What causes feline ischemic encephalopathy?

Complete and total vascular occlusion causing an infarction

How can cuterebra cause feline ischemic encephalopathy?

Cuterebra migrates to the olfactory bulb causes a vascular spasm and infarction

What are the two responses after feline ischemic encephalopathy?

Meninges fibrosis and contract

Parenchymal response collapses and forms cysts with secondary hydrocephalus

Meningial response to infarction

Parenchymal response to infarction

What are the two types of cerebral edema?

Cytotoxic edema

Vasogenic edema

What is cytotoxic cerebral edema?

Blood brain barrier is altered due to a toxin or metabolic dz

What is vasogenic edema?

Regional brain swelling due to infarcts, inflammation, neoplasia, or trauma

What causes cytotoxic edema?

Energy-dependent sodium and potassium pumps in endothelial and glial cells are impaired

What does cytotoxic edema look like?

Diffuse swelling of the brain

What is vasogenic edema?

Regional brain swelling due to infarcts, inflammation, neoplasia, or trauma

What causes vasogenic edema?

Physical disruption of the tight junctions between endothelial cells of BBB increasing vascular permeability and leakage of serum proteins into intracellular space

What does vasogenic edema look like?

Asymmetric or localized swelling precipitated by inciting lesion

Vasogenic edema