Causes of Brain Dysfunction (Part 2) Flashcards
3 types of infections of the brain
- bacterial infections
- viral infections
- parasitic infections
bacterial infections
- When bacteria attack the brain (encephalitis), they often lead to the formation of cerebral abscesses (pus pockets)
- Bacteria often attack the meninges, producing an inflammation called meningitis
- Syphilis: a type of bacteria that can attack the brain
- General paresis: the syndrome of psychosis/dementia that results from a syphilitic infection of the brain
viral infections
- 2 types:
- those with affinity for neural tissue (ex. rabies)
- those that attack all tissues indiscriminately, including neural tissue
Rabies
- virus must get into motor neurons and then up into brain -> “retrograde mechanisms”
- Symptoms: aggression, hydrophobia, fever, lethargy, etc.
parasitic infections
- toxoplasma gondii: eukaryotic parasite, 1/3 of humans have it (can lead to toxoplasmosis)
- Neurocysticercosis: tapeworm in the brain -> ingested at stage in life cycle where it can cross the blood-brain barrier
neurotoxins
- Heavy metals
- Mercury can accumulate in the brain and permanently damage it – producing a toxic psychosis
- – Mercury is present in vaccines, but no evidence to suggest harmful neurological effects (no relationship between vaccines and autism)
- Lead can also lead to toxic psychosis (“crackpots” from cracked bowls with lead in them -> inhale lead -> psychosis)
Multiple Sclerosis
- Progressive disorder that primarily attacks the myelin of axons in the CNS, but there is also cell loss
- immune system appears to attack the CNS myelin as if it were a foreign substance; immune function is slower
- 2 forms: Relapsing-Remitting and Primary Progressive
MS: progression of Relapsing-Remitting form
1) Clinically isolated syndrome (ie. You get numbness for a while, and then it goes away)
2) Relapsing-remitting (where you’ll recurring episodes, then it’ll go away for a bit)
3) Secondary progressive MS
- Cellular degeneration continues all the way through, immune response is high during RRMS in response to white matter cells dying, immune response is lowered during SPMS because there’s just too much degeneration
MS: Progression of Primary Progressive Form
Similar to secondary progressive (incl. immune function), but there’s no relapsing-remitting stage beforehand
MS: common symptoms in advanced cases
- visual disturbances
- muscular weakness
- Numbness
- Tremor
- loss of motor coordination
MS: Predictors/risk factors
- Getting Epstein-Barr virus (mono) as a teenager or adult increases your likelihood of getting MS
- Geography: Much more likely to occur in people that spent the first 15 years of their lives in cold climates
- Vitamin D: some evidence for relationship between vitamin D and MS (lower levels of vit. D in people living in cold countries)
- Genetics: some variance can be described by genes, but not a lot -> substantial environmental factors
MS: 2 theories
- Outside-In theory: Primarily an autoimmune disease -> neuroinflammation (abnormal immune response) is causing neurodegeneration (cell loss)
- Inside-Out theory: Primarily a neurodegenerative disease -> neurodegeneration (cell loss) is causing neuroinflammation (immune response)
MS: Potential Treatments
- Maybe vitamin D supplements
- Corticosteroids
- Immune system modulators
- Cannabis
- Physical therapy
- Muscle relaxants
toxoplasma gondii
- parasite found in cat intestines -> excreted through feces, can then infect rats and sometimes people
- “manipulation hypothesis” -> changes rats’ behaviour by alterting amygdala activity
- activates attraction pathways in rat brains in response to cat urine, which normally elicits fear response -> reduced fear of cats
- in order to toxoplasma to complete life cycle and reproduce, rats have to be ingested (so parasites can go back to intestines) -> loss of fear in rats makes that easier
