The document discusses various cellular responses to stress and injury, including adaptations, reversible injury, and cell death. It describes cellular adaptations like hyperplasia, hypertrophy, and atrophy that allow cells to respond to increased or decreased demands. Reversible injury does not cause permanent damage if the stressor is removed. Irreversible injury and the two types of cell death, necrosis and apoptosis, represent permanent damage. Necrosis is caused by external factors and results in inflammatory cell death, while apoptosis is a regulated mechanism of cell removal. The targets of injury are aerobic respiration, cell membranes, protein synthesis, cytoskeleton and DNA.