Stage of Adaptive Mechanism Failure
At this stage, the body's protective and compensatory reactions lose effectiveness, while the damaging action of the extreme factor increases. Functional systems disintegrate, metabolism is disrupted, plastic processes are inhibited, and cell and tissue structures are damaged. Most homeostatic parameters deviate critically from normal ranges.
Due to the exhaustion of adaptive mechanisms, critical organs and systems suffer:
- Nervous system: disorders of sensation, movement, integration, and higher nervous activity.
- Cardiovascular system: arrhythmias, ischemia, heart failure, and capillariotrophic failure.
- Blood system: deterioration of blood flowability and viscosity, cell aggregation, the sludge phenomenon, and thrombohemorrhagic complications.
Pathological Vicious Circles
Under conditions of adaptive failure, closed pathological loops (circulus vitiosus) are formed. The initial factor triggers a cascade of disturbances that, via positive feedback, amplify the primary cause.
Key examples of such processes include:
- Hemodynamic collapse: inadequate vasodilation and blood pooling lead to a drop in circulating blood volume (CBV), decreased venous return and cardiac output, which further reduces CBV.
- Cellular level: hypoxia and the suppression of antioxidant defense stimulate lipid peroxidation (LPO) and the accumulation of reactive oxygen species. This damages respiratory and glycolytic enzymes, worsening tissue oxygen deprivation.
Multiple Organ Dysfunction and Homeostasis
Pathological progression leads to profound multiple organ damage:
- Kidneys: filtration and secretion are impaired, leading to oliguria or anuria progressing to uremia.
- Liver: protein, lipid, and carbohydrate metabolism suffer, along with detoxification function and the blood coagulation system.
- Gastrointestinal tract: motility and secretion are suppressed up to the point of paresis, with developing malabsorption, intestinal autoinfection, and autointoxication.
Critical deviations in homeostatic parameters include a drop in $pO_2$, acidosis, blood pressure fluctuations, and electrolyte imbalances.
Stage of Extreme Life Regulation
When energy resources are depleted and deafferentation of central and peripheral structures deepens, the terminal stage occurs. Functional systems finally disintegrate, and the organism drops to a primitive metabolic level of regulation.
- Without treatment: escalating disorders lead to a terminal state and death.
- With effective therapy: the pathological process can be halted, restoring normal body function.