What deep metabolic and structural disturbances occur in cells during the exhaustion stage?

During the exhaustion stage, sources indicate the following disturbances: "wear and tear" of systems ensuring specific adaptation; a decrease in the capacity of energy and plastic supply systems; and a decline in synthesis processes, structural breakdown, and the repair of nucleic acids and proteins.

Which intracellular second messengers participate in the protein kinase activation cascade during acute stress?

During acute stress, the following cascade is directly confirmed: epinephrine activates Gs-protein and adenylyl cyclase via β-adrenergic receptors; ATP is converted to cAMP, which acts as a secondary messenger and activates protein kinase A. During stage I of emergency adaptation, the levels of local function mobilizers—calcium ions, cytokines, peptides, nucleotides, etc.—also increase, providing direct or indirect activation of protein kinases.

Does the adaptation syndrome always end in exhaustion?

No, the stage of exhaustion is not obligatory. It develops only with repeated exposure to stress or in debilitated patients due to the depletion of energy supply systems.

What is the "systemic structural trace of adaptation"?

This is a complex of changes during the stage of increased resistance, where hypertrophy and hyperplasia of structural elements occur in dominant systems to ensure their reliable performance.

Why can acute stress cause gastrointestinal ulcers or myocardial infarction?

Due to a sharp increase in organ function, energy demand rises, which blood supply fails to match. Relative ischemia develops, leading to dystrophy, necrosis, and the onset of "adaptation diseases".

What is the essence of the steal phenomenon during adaptation?

The body directs maximum energy and plastic resources to dominant systems while limiting the supply of oxygen and metabolic substrates to other, currently less critical systems.

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General Adaptation Syndrome

For medical students2 min readUpdated 2026-10-10

General Adaptation Syndrome (GAS) is a coordinated set of systemic reactions of the body in response to extreme stressors, aimed at restoring homeostasis. It involves the mobilization of the nervous and endocrine systems to avoid threats, overcome their pathogenic effects, or maintain viability under novel conditions.

TriggerAction of an extreme agent and subsequent disruption of homeostatic parameters.

Three StagesEmergency (urgent) adaptation, increased resistance, and exhaustion.

ObjectiveEnhancing resilience and adjusting the body to altered environmental conditions.

Adaptation DiseasesGastrointestinal ulcers, hypertension, and myocardial infarction due to blood supply deficits during acute stress.

Mechanisms and Pathways of the Response

The development of the syndrome begins against the background of a generalized exploratory reaction. When a pathogenic factor acts on the body, central regulatory links—the nervous and endocrine systems—are activated. They form functional systems that mediate the response across three main pathways:

Behavioral (avoidance): The individual actively investigates the environment to escape the source of danger.
Specific: The system directly responsible for combating the specific factor begins operating in overdrive. This leads to the hypertrophy of its structures and the formation of specific adaptation.
Nonspecific: A classic stress response develops, providing general resistance of the body to any stimuli.

Stage I. Emergency (Urgent) Adaptation

The first phase is characterized by the maximal mobilization of all available reserves. It is based on a triad of regular changes:

Activation of exploratory behavior to gather information about the threat.
Hyperfunction of dominant systems (e.g., increased muscle work during physical exertion or enhanced oxygen transport during hypoxia).
Engagement of the nonspecific stress component (cardiovascular, respiratory, immune, and endocrine responses to any irritant).

At the cellular level, hormones (epinephrine, norepinephrine, glucocorticoids, thyroid hormones) and local mediators (calcium ions, cytokines) are released. They activate protein kinases, triggering the breakdown of carbohydrates, fats, and proteins. Cell membranes are modified through the intensification of free radical lipid peroxidation (LPO), which facilitates the transport of ions and substrates.

Important: Due to a sharp surge in energy demand, relative ischemia may occur. This can lead to tissue necrosis and the development of "adaptation diseases" (gastrointestinal ulcers, arterial hypertension, myocardial infarction, immunopathologies).

Stage II. Increased Resistance

If the body successfully survives the first phase, the acute stress response subsides, and sustained adaptation is established.

The main mechanism of this stage is the systemic structural trace of adaptation. The mass and number of structural elements in dominant systems increase (hyperplasia and hypertrophy), making their performance robust and reliable. Cross-adaptation often occurs—resistance develops not only to the primary stressor but also to other extreme factors.

However, the body's resources are limited. Energy and plastic materials are channeled to hyperfunctioning organs at the expense of other tissues. This process is known as the steal phenomenon.

Stage III. Exhaustion

This stage is not obligatory. It occurs when the extreme factor acts for too long, repeats frequently, or resumes after a pause.

"Wear and tear" of the specific defense systems occurs. Energy production drops, protein and nucleic acid synthesis rates fall, and structural restoration is impaired. Debilitated individuals and patients with severe chronic conditions are at the highest risk. If the hypertrophied cells of the dominant systems do not receive sufficient plastic support, they undergo cell death.

Mnemonic

To remember the triad of the first stage, use the rule "E-H-M": Exploratory behavior, Hyperfunction (of dominant systems), Mobilization (of other organs).

Frequently asked questions

What deep metabolic and structural disturbances occur in cells during the exhaustion stage?: During the exhaustion stage, sources indicate the following disturbances: "wear and tear" of systems ensuring specific adaptation; a decrease in the capacity of energy and plastic supply systems; and a decline in synthesis processes, structural breakdown, and the repair of nucleic acids and proteins.
Which intracellular second messengers participate in the protein kinase activation cascade during acute stress?: During acute stress, the following cascade is directly confirmed: epinephrine activates Gs-protein and adenylyl cyclase via β-adrenergic receptors; ATP is converted to cAMP, which acts as a secondary messenger and activates protein kinase A. During stage I of emergency adaptation, the levels of local function mobilizers—calcium ions, cytokines, peptides, nucleotides, etc.—also increase, providing direct or indirect activation of protein kinases.
Does the adaptation syndrome always end in exhaustion?: No, the stage of exhaustion is not obligatory. It develops only with repeated exposure to stress or in debilitated patients due to the depletion of energy supply systems.
What is the "systemic structural trace of adaptation"?: This is a complex of changes during the stage of increased resistance, where hypertrophy and hyperplasia of structural elements occur in dominant systems to ensure their reliable performance.
Why can acute stress cause gastrointestinal ulcers or myocardial infarction?: Due to a sharp increase in organ function, energy demand rises, which blood supply fails to match. Relative ischemia develops, leading to dystrophy, necrosis, and the onset of "adaptation diseases".
What is the essence of the steal phenomenon during adaptation?: The body directs maximum energy and plastic resources to dominant systems while limiting the supply of oxygen and metabolic substrates to other, currently less critical systems.

Go deeper

The role of free radical lipid peroxidation (LPO) in cell membrane modification.
Mechanisms of protein kinase activation by local function mobilizers.
Pathogenesis of cell injury in pathological hypertrophy.
Interaction of specific and nonspecific responses to extreme factors.
Formation of temporary connections and conditioned reflexes during adaptation.