Video narration
How can a blocked blood vessel destroy neurons so quickly, yet leave nearby brain tissue salvageable? Picture a phone losing power: its battery can't run essential systems, so shutdown follows. In an ischemic stroke-about 87% of strokes-a thrombus, embolus, or small-vessel occlusion reduces cerebral blood flow, cutting off oxygen and glucose. ATP falls, so the Na+/K+-ATPase fails. Neurons depolarize; glutamate overstimulates NMDA and AMPA receptors, driving calcium inward. Calcium activates destructive enzymes that dismantle cell structures. Mitochondria fail too, generating reactive oxygen species-damaging molecules that intensify oxidative injury, inflammation, and programmed cell death. Near the blockage, flow below approximately 10 mL/100 g/min defines the ischemic core: irreversibly damaged tissue. But surrounding it is the ischemic penumbra: functionally silent, yet metabolically viable. Restore blood flow promptly, and it can recover. So: ATP failure unleashes calcium-driven destruction, but prompt reperfusion can rescue the penumbra.