Neuronal Death Flashcards
what are 6 reasons neurons die?
we dont need served their purpose error correction pattern formation size matching removal of damaged or harmful cells
what is the most apparent explanation for removing cells we do not need?
sexual dimorphism in the CNA
describe sexual dimorphism in the CNA
anteroventral periventricular nucleus more cell dense in female rodents, and irrespective of male or female- same number of cells created so males must lose cells during developemtn
describe an example of when cells die post to serving their purpose
in species that undergo metamorphosis
tadpoles have tails and frogs have legs- so neurons critical to tadpoles die off when frog becomes mature
what is error correction?
removal of neurons that have not connected with the correct targets
what is an example of error correction?
eyes
projections going to wrong eye are eliminated
there is regulation and if neurites take wrong turn, they die off by apoptosis
what is the order of pattern formation?
NS begins as flat sheet of cells -> neural tube -> complex shaping manaouvers -> brain and NS
what is the best example of pattern formation?
hand
in ducks formation stops earlier- skin between fingers remains
what is an advantage of size matching?
evolutionary
describe removal of damaged or harmful cells
very rare
defence against pathogens
neuron under attack from rabies
what are 5 diseases involving unwanted neuronal loss
parkinsons alzheimers huntingtons stroke mad cow disease
describe neural loss in parkinsons
pigmented cells that synthesise dopamine in healthy brain- has been lost
loss of l dopa
describe neural loss in alzheimers
overall loss of brain mass
describe neural loss in huntintons
loss portions of striatum
describe neural loss from a strokw
areas around blood clot or bleed are extreme damage or loss
describe neural loss in mad cow disease
brain spongey
how do neurons die
apoptosis
necrosis/necroptosis
what is apoptosis
sporadic loss of cells
no inflammatory response
theres a tipping point for speed
what are 6 triggers of neuronal apoptosis
neurotrophic factor deprivation excitotoxity - excess glutamate metamorphosis neurodegeneration exposure to UV deleterious effects of reactive oxygen species
describe excitotoxicity
excess glutamate
glutamate neurotransmitter and so is substance that makes neurons produce electrical signals, too much leads to too excited neurons leading to cell death
what are 6 characteristics of apoptosis
cells shrink in size
nuclear chromatin condenses
dna has laddered appearanc
cell membrane and organelles stay relatively in tact
cytoplasm and nucleus make many apoptopic bodies
apoptopic bodies are phagocytosed(no immune response)
what is necrosis
accidental or pathological injury causes rapid cell death- extracellular signalling may be involved too (necropotis)
initiates an immune response
what stresses can induce necrosis
environmental(heat, infection, O2 deprivation) extracellular signals (receptor, transduction and response, often termed necroptosis)
what are the characteristics of necrosis
cell swelling and metabolic failure
disintegration of cell membrane and organelles
immune reaction
what is pyknosis
chromatin condensation patter in apoptosis
what is necroptosis
extracellular signals mediate necrosis
mediated by death receptor
what are the two death receptors associated with necroptosis
TNF and Fas-L
what is the necrosome
biochemical pathway crucial for necroptosis
what is the deciding point of necrosome
RIP1 a protein
polyubiquitinated
cell death signal chops the poly ubiquitin tail off and it binds to caspase 8
