Extremly low temperature is able to form crystals inside the cell. Mild decrease in temperature causes paralysis of vasomotors and an increase in permeability of vessels. Blood viscosity rises proportionally with the lowering temperature and cells are destroyed by hypoxia. Low temperature acting for a longer time provokes the destruction of myelin in exposed area. Microthrombi are produced in vessels and they are the cause of gangrene .
High temperature increases the permeability of cell membranes.
Very high temperature is responsible for the coagulation of vessels and denaturation of vital biopolymers, especially proteins. According to the dose and the way of exposition ionizing irradiation may primarily damage haematopoietic, gastrointestinal or neural tissues. Whole-body irradiation produces nonspecific immunosupression which is the cause of increased sensitivity to infection. The infection is developed mainly due to leukopenia and the loss of physical integrity of mucosal membranes especially in the gastrointestinal tract. Ionizing radiation is also used for the treatment of patient with cancer and sometimes in the form of local graft irradiation.