stroke Flashcards
describe the types of stroke
ischemic - blockage of blood vessels
hemorrhagic - rapture of blood vessels
strokes are mostly focal (loss of blood supply to a certain area of the brain) but can also be global (caused by cardiac arrest)
describe the risk factors for stroke
diabetes
hypertension
atherosclerosis
genetic polymorphisms
describe penumbra
around the infarct/ core zone of necrotic tissue is called the penumbra. these nerve cells die slower (24-72hrs) via apoptosis
causes of necrosis
cell lysis
causes of delayed cell death
- massive release of glutamate (saturation)
- influx of intra-cellular calcium
- free-radical production
- activation of brain macrophages (microglia) releasing NO, superoxide, cytokines
- activation of intrinsic apoptotic mechanisms
etc
excitatory theory
explains how neurons die during stroke. Excessive activation of glutamate in the brain causes nerve cell death, transporters become saturated.
glutamate receptors
- Ionotropic (ion channels): AMPA/kainate; NMDA
2. metabotropic - G-protein linked
AMPA receptors
ligand-gated ion channel
- glutamate binds causing an influx of Na+ and nueronal depolarization
- GluR1-4
kainate receptors
ligand-gated ion channel
- glutamate binds causing an influx of Na+ and nueronal depolarization
- GluR5-7
NMDA receptors
both ligand-gated & voltage-gated
- glutamate binds causing the channel to open and an influx of Ca2+ which depolarizes the neuron
- When polarized, Mg2+ occupy and block the channel
- Depolarization leads to Mg2+ efflux (hence voltage-dependent)
PCP (phencyclidine, ‘angel dust’) binds inside the channel and blocks ion flow (non-competitive antagonists)
metabotropic - G-protein linked
mGluR 1&5
-activate phospholipase C and depolarize neurons
mGluR 2&3
-inhibit adenylate cyclase and cause inhibition of NT release
