Lecture 32: Nervous 1 Flashcards
What are the parts of a neuron
cell body
axon
dendrite
What are the 3 main functions of a neuron
transmit electrical and chemical signals
regulate impulses
axonal transport
What cell type makes up most of the CNS
astrocytes
What are the 3 functions of astrocytes
regulation
repair
form barrier
What is the glia limitans
The foot processes of astrocytes
What are microglia
CNS immune cells
What is the function of oligodendrocytes
make CNS myelin
What is the functions of the choroid plexus
makes CSF
What is the functions of ependymal cells
moves CSF through the ventricles
What is the gross appearance and function of CSF
clear fluid
protection - absorb shock
transports nutrients and removes waste
What is the pattern of flow of CSF in the CNS
lateral ventricle
3rd ventricle
mesencephalic aquaduct
4th ventricle
subarachnoid space
circulates multiple times per day
What are the layers of the meninges
dura mater (adhered to periosteum)
subarachnoid space
pia mater (attached to nervous tissue)
What makes up the blood brain barrier? Which is the key element
astrocyte foot processes/glia limitans
tight junctions in the endothelium
- this is the key element
blood vessel basement membrane
What are the leptomeninges
the arachnoid membrane and the pia mater
What feature of the blood brain barrier is key to its function
specialized transport systems in the cells
What features of neurons make them susceptible to injury
they have low glucose stores
very susceptible to free radicals
high metabolic rate
- they will die fast
Order, neurons, endothelial cells, and support cells in order of susceptibility to injury
high
neuron
support cell
endothelial cell
low
Describe the regeneration capacity of neurons
neurons/axons in the CNS have no ability to regenerate
- injury will result in neuro deficit/paralysis
in the PNS there is some ability to regenerate but it requires
- axonal transport
- nerve must be aligned
What is another name for axonal damage
wallarian degeneration
What causes wallarian degeneration? What are the gross features
many causes
- trauma
- toxin
- compression
reduces axon function and causes axonal swelling and myelin degeneration
- macrophages digest
What is the main mechanism of injury caused by space occupying lesions in the CNS?
there is no ability for tissues to expand
What are examples of causes of space occupying lesions in the CNS? What are the clinical consequences?
neoplasia
abcess
hemorrhage
hydrocephalus
the clinical effects are dependent on what part of the CNS is affected
How would you describe the ability of the CNS to resist infection
poor
if the organism is able to cross the BBB there are few mechanisms to strop it
What cell type facilitates healing in the CNS
astrocytes
but they cannot form strong capsules and so they break easily
Describe 2 ways a neuron could die? Why might each occur?
apoptosis
- normal proccess
- removing old cells
- can be a feature of disease
necrosis
- multiple cells involved
- will cause inflammation
- it is a response to injury (cerebral ischemia/inflammation/toxin…)
What is the consequence of chronic neuronal loss
cerebral cortical atrophy
What is cerebral cortical atrophy? What might cause it?
slow and progressive neuronal loss without the presence of inflammation
due to
- aging
- pigment accumulation (ceroid-lipofuscinosis)
- neurodegenerative disease
can occur in any species
What is result of oligodendrocyte damage and what is the consequence?
demyelination
causing slower signalling and neurologic signs
What can cause demyelination of oligodendrocytes
virus
iscemia
lead toxicity
autoimmune
What is an infarct and what does it look like grossly in the CNS?
is it the rapid onset of ischemia
- if slow onset there is compensation with collateral flow
hemorrhagic grey matter
pale/soft white matter
What causes congestive brain swelling? What is the consequence?
due to vasodilation
- maybe from trauma
rapid and severe increase in intracranial pressure
What is a subdural hematoma? What does it cause
it is focal hemorrhage between the dura and leptomeninges (arachnoid membrane and pia)
causing increase intracranial pressure
What is cytotoxic cerebral edema and what causes it
intracellular accumulation of fluid from altered cell metabolism
usually due to ischemia
What is vasogenic cerebral edema and what causes it
extracellular fluid accumulation from BBB breakdown
What is hydrostatic cerebral edema and what causes it
extracellular fluid accumulation from increased HP
What is hypo-osmotic cerebral edema and what causes it
extracellular and intracellular fluid accumulation from reduced OP
What is the gross appearance of cerebral edema
flat and swollen gyri and sulci
there can be herniation of the vermis of the cerebellum through the foramen magnum
List the 4 main portals of entry into the CNS
direct extension (ear/nasal/osteomyelitis)
hematogenous (septicemia)
leukocyte trafficking
retrograde axonal transport
What type of portal of entry does Strep suis use into the CNS? What are the sequelae?
hematogenous
suppurative meningitis
fibrinous peritonitis
interstitial pneumonia
What portal of entry does HPAI use into the CNS? What are the sequelae?
leukocyte trafficking
causing meningoencephalitis
What are the defense mechanisms of the CNS
skin
meninges
BBB
glia limitans
microglia
How do pathogens enter the BBB
they disrupt the BBB
allow other inflammation cells in and also increase tissue compromise
What type of pathogen causes suppurative inflammation
bacteria
What type of pathogen causes granulomatous inflammation
fungi
protozoa
soma bacteria
What type of pathogen causes lymphoplasmacytic inflammation
virus
protozoa
What type of pathogen causes eosinophilic inflammation
parasite
Define encephalo-
brain
Define -leuko
white matter
Define malacia
softening
Define -myelo
spinal cord
Define -meningo
meninges
Define poliencophalomyelitis
inflammation of grey matter in brain and spinal cord
Define meningoencephalitis
inflammation of meninges and brain
What are the portals of entry of bacteria causing a brain abscess
direct extension and hematogenous
What are the clinical consequences of brain abscesses? What is the mechanism of injury
it is location dependent
the mechanism of injury is due to tissue destruction and space occupying damage
result in abnormal mentation
ataxia
head tilt
circling
blind
cardiac and/or resp dysfxn
What are the gross lesions of a brain abscess
single or multiple
a center of necrosis with a thin capsule
- the capsule can be fibrotic if it is near the meninges
can have herniation of the cerebellum through the foramen magnum
Where are brain abscesses located usually and why?
usually occur at the grey-white matter interface because there is increased blood flow and the vessels turn horizontally
What might cause brain abscesses in small ruminants
dehorning
What brain lesion does Strep equi equi cause and what is its route of entery
brain abscess
hematogenous
What is the main manifestation of spinal cord/vertebral abscesses
discospondyliosis
due to bacterial emboli lodging between vertebrae > they extend and spread to the intervertebral discs causing abscess which compresses the spinal cord
What is ependymitits and choroid plexitis
inflammation of the ependymal cells and/or choroid plexus
What is the route of entry for bacteria causing ependymitis and choroid plexitis
hematogenous
direct
enter CSF
Whhat are the lesions associated with ependymitis and choroid plexitis
purulent CSF
hemorrhage/hyperemia
spread to meninges
hydrocephalus if the flow is obstructed
What causes meningitis? Give 2 example. How do they enter
bacteria
- e coli
- streptococcus
hematogenous
direct extension
leukocyte trafficking
What causes neonatal septicemia? How does it enter the body? How does it spread to CNS
bacteria
oral intrauterine
umbilical
post surgical
inhale
failure of passive transfer
spread to CNS hematogenously
What are the clinical consequences of neonatal septicemia
fibrosuppurative inflammation on serosa
cause
- meningitis
- arthritis
- synovitis
- polyserositis
result in vascular leakage of fibrin
What are the gross lesions of neonatal septicemia
congestion
hemorrhage
opacity of meninges
fibrin in the ventricles
What are the 4 main agents that cause neonatal septicemia in calves
e coli
strep
pasturella
mannheimia
What are the 3 main agents that cause neonatal septicemia in foals
e coli
strep
staph
What are the 3 main agents that cause neonatal septicemia in lambs
e coli
pasturella
mannheimia
What are the 4 main agents that cause neonatal septicemia in pigs
haemophilus parasuis
e coli
strep
staph
What is the causative agent of glassers disease and what are the clinical manifestations?
haemophilus parasuis
finbrinosuppurative polyserositis, polyarthritis, meningitis
= neonatal septicemia
What damage does hepes cause to the CNS? What is its mechanism of damage
necrosis of neurons and glial cells and vascular endothelium
inflammation is the main mediator of damage
How does herpes enter the CNS
retrograde axonal transport mainly
also hematogenous and leukocyte trafficking
it remains latent in the trigeminal ganglia and can reactivate
What is the causative agent/disease manifestation of herpes in horses, bovine, and pigs
horse: EHV1
bovine: malignant cattarhal fever or infections bovine rhinotracheitis
pig: pseudorabies
How does rabies enter the body? What does it infect?
enter via bite
infects brain and non-nervous tissue like salivary glands synchronously
What are the clinical signs of rabies? How do they differ for large animals?
aggression
irritable
anorexia
hydrophobia
paralysis
LA: lameness and colic
What is the 6 steps of rabies pathogenesis
bite and replicate in muscle
enter peripheral nerves
retrograde transport to dorsal root ganglia
enter spinal cord and ascend
enter bran via ascending and descending fibres
spread via cranial nerves to the eyes and salivary glands
What are the gross lesions of rabies infection
none
What are the histo lesions of rabies infection
non suppurative meningoencephalitis
inclusion bodies
neuronal cell death
What sample is needed for rabies diagnosis
brain and brainstem (intact)
What are 3 main types of fungi that cause CNS disease
aspergillus
candida
mucor
What is 1 type of algae that causes CNS disease
blue-green algae aka prototheca
What parts of the body does blastomyces dermatitidis infect
skin
lung
bone
sometimes CNS
What parts of the body does Coccidioides immitis infect
skin
lung
bone
sometimes CNS
What parts of the body does Histoplasma capsulatum infect
skin
lung
bone
sometimes CNS
from bat feces
What parts of the body does cryptococcus neoformans/gatti infect? What species is most affected?
cats mainly (also dogs and horses)
has a tropism for the CNS
What are the hosts associated with neospora caninum
definitive host = canid
intermediate host = herbivores
canids ingest infected tissue of herbivores
How does neospora caninum enter the CNS and what kind of lesions does it cause?
leukocyte trafficking
causes multifocal necrosis and pyogranulomatous inflammation
What is the clinical manifestation of neospora caninum in puppies and horses respectively
puppies:
- polymyositis
- myocarditis
- dermatitis
horses
- meningoencephalitis
What are the hosts associated with toxoplasma gondii
definitive host: felids
intermediate hosts: wide range
How does toxoplasma gondii enter the CNS? What is its pathogenesis
hematogenous spread
endothelial infection leads to vascultits
- causes hemorrhage and necrosis
- resulting in inflammation
What are the clinical consequences of toxoplasma gondii infection in animals in utero and in older animals
in utero: cause necrosis in CNS
older: causes inflammation and polyradiculoneuritis
What is myasis
insect larvae infection
What are 3 examples of parasites that can cause myasis
oestrus ovis (sheep nasal bot)
hypodermic bovis
- migrate and enter spinal cord or cause inflammation in the spinal cord if anthelminth kill it
cuterebra: rabbits and rodents usually
What is the mechanism of damage to the CNS of cestodes (tapeworms)
migrate and form cysts causing space occupying damage
What animal is most affected by tania multiceps? What form causes the damage? How does it enter the CNS?
sheep mainly
the larvae - coenuris cerebralis
- hematogenous spread to the CNS
- encyst and cause space occupying damage
Nematodes can cause CNS problems. What is more severe aberrant migration of the nematode or migration in aberrant host?
migration in the aberrant host
What are the lesions associated with nematode damage
linear or serpentine tracts of necrosis and hemorrhage
might see the visible parasite
Give 2 examples of nematodes causing CNS problems. What species do they affect?
Baylisasceris procyonis - raccoons
angiostrongylus cantonensis - rats
What are prions? What type of disease do they cause?
proteinaceous infectious particles
transmissible spongiform encephalopathies
How are prions transmitted
ingestion of CNS material
or CWD is also transmitted via saliva, blood, and urine
How do prions enter the CNS
leukocyte trafficking
hematogeous
What are the lesions associated with prions
no gross lesions - no inflammation
they will accumulate in neurons - vacuolate neurons
Give 3 examples of prion disease
scrapies
BSE
CWD
