Insult

This is an acute focal disturbance of brain function characterized by a complex of clinical symptoms (loss of consciousness, paralysis, cognitive and other impairments). It is caused by a focal brain injury. There are ischemic strokes caused by impaired arterial blood flow due to thrombosis of brain arteries, emboli, atherosclerotic plaques, and hemorrhagic strokes when blood leaks into the brain. It has been found that the brains of people who have died from a stroke have an unusually high level of glutamate. Due to hypoxia, less frequently other causes, glutamatergic neurons release unusually high amounts of glutamate, which activates NMDA and AMPA receptors. Active AMPA receptors act as Na⁺ channels, partially depolarizing the postsynaptic membrane. This activates NMDA receptors, through which Ca²⁺ flows into the postsynaptic neuron, raising the concentration of these ions to a toxic level inside the cell. It is believed that neurons die due to the activation of proteases and phospholipases caused by Ca²⁺ overload. Ca²⁺ can also damage neuronal mitochondria and disrupt ATP synthesis. Additionally, radical reactions are activated, irreversibly damaging vital neuronal structures and functions.

Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė