Nervous System Flashcards
What % of human genes are associated with the nervous system?
50% at least
What cells in the nervous system are the most sensitive to injury?
Neurons
What is selective vulnerability?
A group of neurons that are functionally related may be selectively injured by a particular type of insult
What part of the brain is most damaged by Alzheimers?
Hippocampus
Which cells are most vulnerable to the effects of mercury?
Cerebellar granular neurons
What cells are targeted by polio?
Anterior horn cells
Axon and dendrite repair is generally limited to what part of the nervous system?
PNS
Review: what is pyknosis?
Nuclear shrinkage in response to cell injury
Review: what is karyorrhexis?
Nuclear fragmentation or breakdown in response to cellular injury
Review: what is karyolysis?
Nuclear dissolution in response to cellular injury
What are red neurons? What are the causes?
What are the effects?
Acute neuronal injury
Causes: ischemia, overwhelming infection, toxicity
Effects: pyknosis then karyorrhexis
What is central chromatolysis?
The axonal reaction - reactions in the cell body appearing with axonal regeneration
What is Wallerian degeneration?
Changes in the distal axon of an injured neuron in the PNS.
- degeneration of axon & myelin sheath
- cellular responses leading to clearing of debris
- activation of regeneration-associated genes (RAGs)
- Schwann cell activity
Review: what is anteriograde degeneration?
Disintegration of the distal axon (usually following neuronal or axonal injury)
What are the cellular effects of atrophy and degeneration of nerve cells?
- reduction in size
- lipofuscin deposits
- neuronal death
- necrosis
Neurodegenerative disorders may result in what inside affected cells?
Inclusions / intra-neuronal deposits
Inclusion bodies: what are neurofibrillary tangles? What diseases produce them?
Twisted cytoskeletal fibers containing ubiquitin and other proteins.
Typical of:
- Alzheimer’s
- Parkinson-dementia complex
Inclusion bodies: what are Lewy bodies? What disease are they associated with? Where do they tend to be located in the brain?
Spheroids made of ubiquitin
Associated with Parkinson’s
Located in the substantia nigra
Inclusion bodies: what are Negri bodies? What disease are they associated with?
Virus inclusion bodies in infected cells
Associated with rabies
Inclusion bodies: what are lipofuscins? What conditions are they associated with?
“Wear and tear” pigments
Associated with aging, chronic hypoxia, and atrophy
Inclusion bodies: what metabolic storage disease leads to accumulation of gangliosides?
Tay-Sachs disorder
Inclusion bodies: what metabolic storage disease leads to accumulation of sphingomyelin?
Neimann-Pick’s disorder
What causes a cherry red spot in the fovea?
Degeneration of neurons of the retina —> leads to a thinning of the macula, allowing the vascularized choroid to show through
Rank the glial elements sensitivity to hypoxia
Oligodendrites
Ependymal cells
Astrocytes
Microglia
Review: what is the function of oligodendrites?
Secretion of myelin in the CNS
Review: what is the function of astrocytes?
Metabolic support
Formation of blood/brain barrier
Triparte synapse formation
Calcium wave communication between astrocytes across long distance
Review: what is the function of microglia?
CNS immune cells
Review: what is the function of ependymal cells?
Secretion of CSF
What are causes of increased intracranial pressure?
- Space occupying lesions (tumor, infection, etc)
- Edema or swelling
- Hydrocephaly
Review: what is swelling of the optic disc called?
Papilladema
What is hydrocephalus?
Increased volume of CSF
Dilated ventricles
Usually results in increased intracranial pressure
Usually related to imbalance between rates of production and absorption of CSF
Review: CSF
List the flow of CSF from production through reabsorption
Ependymal cells in the choroid plexus of the lateral ventricle —> lateral ventricles —> intraventricular foramina of Monro —> 3rd ventricle —> cerebral aqueduct of Silvius —> 4th ventricle —> lateral apertures (foramina of Luschka) OR median aperture (foramen of Megendie) —> subarachnoid space —> arachnoid granulations —> venous sinuses
What is obstructive or non-communicating hydrocephaly?
Blockage of CSF circulation, generally trapping CSF in the ventricles and preventing it from reaching the subarachnoid space
Review: what are foramen of Magendie? What are foramina of Luschka?
Magendie = central aperture of 4th ventricle, connecting to the cistern magna
Luschka: lateral aperture of 4th ventricle, connecting to the subarachnoid space
What is communicating hydrocephaly?
CSF enters the subarachnoid space but circulation or absorption is blocked
- scarring in subarachnoid granulations or meninges
- thrombi or other obstructions of dural sinuses
What kind of hydrocephaly does not include increased intracranial pressure? Why?
Hydrocephaly ex vacuo
Brain atrophy leaves space for ventricular swelling
What are early symptoms of hydrocephaly?
The symptoms of increased intracranial pressure in general:
- headache
- mental dullness
- potential nausea and vomiting
What are advanced symptoms / clinical findings of hydrocephaly?
- papilladema
- herniation of brain tissue, esp through foramen magnum
What is a concussion?
Closed head trauma —> indications of injury are typically absent. No bleeding, etc.
Associated with transient loss of consciousness, altered reflexes, etc.
What is contrecoup?
Head trauma where the damage is in parts off the brain opposite to the impact site. May be caused by brain tissue rebounding into the skull.
Brain trauma without injury to cranium (6):
- Contusion (interstitial bleeding, aka bruising)
- Laceration (tearing of brain surface with bleeding)
- Concussion
- Rotary motion with shearing
- Contrecoup
- Cord trauma
What are the two major classes of CNS infections?
- Meningitis
- Encephalitis
*progression from one to the other is possible
What are the 3 categories of meningitis?
- Acute pyogenic (bacterial)
- Acute lymphocytic (viral)
- Chronic
What type of meningitis is more common?
Viral
Bacterial causes of meningitis?
N. Meningitidis E. Coli H. Influenzae b S. Pneumoniae S. Agalactiae
CSF findings in acute pyogenic (bacterial) meningitis?
- Elevated polys (polynuclear cells - aka neutrophils)
- Reduced glucose
- Elevated proteins
(Both due to bacterial metabolism) - Bacteria present
Common causes of viral meningitis?
- mumps
- ECHO viruses
- Epstein-Barr
- Herpes simplex
CSF findings in acute lymphocytic (viral) meningitis?
- elevated lymphocytes
- moderately elevated proteins
- normal glucose
Common causes of chronic meningitis?
- TB
- fungi
- brucellosis
What are common causes of encephalitis?
- viral
- slow virus
- prion diseases (unconventional agents)
What is encephalitis?
Infection of brain parenchyma
What is tropism (referring to encephalitis)?
Selectivity of damage inflicted by certain viruses - ie: polio is most likely to destroy anterior horn cells.
What viruses are common causes of encephalitis?
- arbor viruses (ie West Nile)
- childhood infections including measles, rubella, chicken pox
- herpes
- polio
- rabies
- hiv
What rare condition may follow childhood measles, eventually leading to dementia and motor disturbances?
Subacute sclerosing panencephalitis (SPPE)
Prion diseases lead to what classic presentation of brain tissue?
Spongiform degeneration - microscopic vacuolization of brain tissue
What 2 prion diseases lead to spongiform degeneration?
What are their causes?
- Creutzfeldt Jacob disease: caused by spontaneous or hereditary mutations, or exposure to tissue containing these mutations through transplant or contact with infected tissue
- Kuru: cannibalism in New Guinea
What is a prion protein?
PrP (prion proteins) are mutated forms of normal membrane glycoproteins —> usually a conversion from alpha-helix folding to beta-sheet folding
How do prion diseases propagate?
Mutated prions appear to induce the mutation in normal proteins when they come in contact, so the disease spreads without a live pathogen.
Mutations in prion regulatory genes are implicated in hereditary conditions.
Review: what is Pott’s disease? What is the resulting deformity called?
Collapse of the vertebral column as a result of TB
The collapsed column is called a gibbous deformity
What are granulomas?
Focal nodular infections consisting of macrophages, etc.
May give rise to expanding lesions
What causes granulomas?
- TB
- fungi
What are common avenues for CNS infection?
- sinus, eye, or ear infections
- dental work
- damage to the back of the throat, like a puncture wound
- peripheral nerve infections (like rabies or herpes)
What is a stroke?
Focal loss of neurological function of vascular origin which lasts more than 24 hours or leads to death
What is a transient ischemic attack (TIA)?
Sudden, focal, reversible neurological disturbance due to disruption of blood supply lasting less than 24 hours
*A TIA is a short stroke!
Focal ischemic infarct is the most common cause of stroke (75-90%). What is it?
- atherosclerosis
- thrombi or emboli related to atherosclerosis
- aneurysms
- inflammation
What are other causes of stroke besides focal ischemic infarct?
- ischemic encephalopathy —> generally ischemia of the entire brain, resulting from heart failure, shock, or another extreme hypotensive event
What is the chief complaint for someone with a subarachnoid hematoma?
Worst headache they’ve ever had in their life
What are the CSF findings for subarachnoid hematomas?
<24 hours = bloodstained
>24 hours = xanthocrhomia
What is the most common cause of an epidural hematoma?
Rupture of the middle meningeal artery
What is the “lucid interval”?
The early stage of a epidural hematoma, during which neurological symptoms are absent
What vessels are associated with a subdural hematoma?
Communicating or bridging veins that connect the cortex to the venous sinuses
Besides trauma, what is a cause of subdural hematoma?
Brain atrophy —> as the brain shrinks, the veins collapse down to the surface and are stretched too far
What is the symptom onset for subdural hematomas?
Slow and progressive, usually starting 48 hours after trauma
What are the classic signs are Parkinson’s?
- stooped posture
- festinating gait
- cogwheel rigidity of limbs
- sluggish voluntary movement
- pill rolling tremor
- rigid or expressionless face
- mask like facies
What part of the brain / which neurons are dominantly affected by Parkinsons?
Dopamine-producing pigmented neurons of the substantia nigra
What deposits form in Parkinson’s, and what are they made of?
Lewy bodies - filamentous deposits of ubiquitin, parkin, and more
Most Parkinson’s is idiopathic, but secondary Parkinson’s may be related to what conditions?
- encephalitis
- exposure to dopamine agonists (like contaminated street drugs)
- repeated head trauma (boxers)
Idiopathic dementia is also called what?
Alzheimer’s Dementia (AD)
May also be related to MS and Parkinson’s
Effects of dementia include:
And what are the ABCs
- memory loss
- poor judgement
- delusions of grandeur
- disorientation
ABC’s
Activities of daily living
Behavior & personality changes
Cognition - thinking, reasoning, learning, memory
Primary physical symptom or characteristic of dementia is…
Progressive brain atrophy, may be accompanied by hydrocephaly ex vacuo
What collects in the brain in dementia? Where?
Neuritic plaques or neurofibrillary tangles of amyloid proteins (alpha-beta amyloids)
Dominantly collect in the hippocampus
What is ALS? What is it’s common name?
Amyotrophic lateral sclerosis (ALS) or Lou Gehrig’s disease
ALS is a common disorder of what?
Motor Neurons - both UMN and LMN
Typically, where are the neurons affected by ALS located?
- Anterior horn of cord
- Cranial motor nuclei
- UMN (Betz cells)
Review: which are the bulbar nerves?
What areas or structures are part of the bulbar region?
Bulbar region = medulla and part of the brainstem (but NOT the midbrain) and the cerebellum
Cranial nerves 9-12 are the bulbar nerves
What is the most common neurological disorder among young adults?
MS
What kind of antigens are commonly seen in MS patients?
HLA Class D
Neurosyphilis is part of which stage of the disease? What are the common neurological symptoms?
Tertiary syphilis
- paresis due to progressive neuronal loss
- tabes dorsalis (fibrosis of dorsal columns of spinal cord) leading to locomotor ataxia and muscular atrophy
Review: what are syphilitic lesions called?
Gummas
What percentage of bone cancer is from metastatic spread?
70%
Review: What are the most common types of primary bone cancers?
- osteosarcoma
- Ewing’s sarcoma
- Giant cell tumor (remember: soap bubble appearance)
Describe most primary tumors of affecting the CNS
Extra-axial = they arise outside the CNS and cause some kind of compression, resulting in nervous system effects —> in the meninges, nerve sheaths, or pituitary or pineal gland
What are intra-axial tumors?
Tumors that arise within the CNS itself
In adults, where are most intra-axial tumors located? How is this location described?
70% are in the cerebral hemispheres
Supratentorial
In children, where are the majority of intra-axial tumors located? What is this called?
70% are in the cerebellum, which is referred to as infratentorial
What are the types of gliomas?
- astrocytoma
- glioblastoma
- ependymoma
- oligodendroglioma
What is a pheochromocytoma?
What are their consequences?
Epinephrine-producing adenoma (tumor of a gland)
Lead to increased HR, BP, etc because of the excess epinephrine
Review: what is a neurilemma?
The nerve sheath
Review: what is Wallerian degeneration?
The degeneration that occurs in the distal segment of an injured axon —>
- Typically a response to mechanical -injury (crushing or cutting)
- debris is cleared by phages
- swelling, chromatolysis, etc.
- regeneration is dependent upon neuron survival, maintenance of the neurilemma, growth factors, and more
What are the differences between polyneuropathy and mononeuropathy?
Poly
- usually bilateral, affects multiple nerves in a wide pattern
- Often caused by disease.
- affects the longest nerves the most, therefore distal extremities
Mono
- usually just one nerve, often follows a dermatomal pattern
- Usually unilateral. Often caused by injury or isolated pathology
Beriberi disease is caused by what deficiency?
What does it cause
Thiamine —> B1
What vitamin deficiency can cause symptoms similar to diabetic neuropathy?
B12
What is Bell’s palsy? What nerve(s) are affected?
Paralysis of CN VII (Facial) usually caused by inflammation of some kind
What is Guillian-Barre syndrome?
Most common acute paralytic disease of young adults (in the US)
Guillian-Barre is idiopathic, but may be a sequela of what conditions?
- acute influenza
- epstein barr
- HIV
What is tic douloureux?
What is its main symptom?
Idiopathic neuralgia
Spontaneous episodes of lighting pain in one or more divisions of CN V (trigeminal)
