Physiology of Stress – Critical Care & Emergency Nursing

Vocabulary flashcards covering key terms, hormones, physiologic concepts, and health consequences related to the stress response for critical care nursing students.

Stress

A perceived or anticipated threat that disrupts homeostasis and exceeds an individual’s capacity to meet demands.

Homeostasis

The body’s tendency to maintain a stable internal environment.

Hypothalamic-Pituitary-Adrenal Axis (HPA)

Neuroendocrine system in which the hypothalamus releases CRH, the anterior pituitary releases ACTH, and the adrenal cortex secretes cortisol during stress.

Autonomic Nervous System (ANS)

Neural network composed of sympathetic and parasympathetic branches that rapidly modulate organ function in response to stress.

Sympathetic Nervous System (SNS)

Branch of the ANS that triggers rapid release of catecholamines and initiates the fight-or-flight response.

Parasympathetic Nervous System (PNS)

Branch of the ANS that opposes the SNS and promotes recovery, adaptation, and energy conservation.

Immune System (in stress)

Third major stress system; interacts with neuroendocrine pathways and alters cytokine profiles during stress.

General Adaptation Syndrome (GAS)

Selye’s three-phase stress model: alarm, resistance (adaptation), and exhaustion (allostatic overload).

Alarm Phase

Initial GAS stage marked by SNS activation and catecholamine surge (‘fight-or-flight’).

Resistance Phase

GAS stage with sustained cortisol and catecholamine release to overcome prolonged challenge.

Exhaustion Phase

Final GAS stage where physiologic resources are depleted, leading to disease susceptibility.

Allostasis

“Stability through change” – the process of achieving homeostasis via physiologic or behavioral change.

Allostatic Load

Cumulative wear and tear on the body from repeated allostatic responses.

Allostatic Overload

Pathologic state when chronic activation of allostatic mechanisms precipitates disease.

Catecholamines (CAs)

Stress hormones (epinephrine, norepinephrine) released from adrenal medulla and sympathetic nerves.

Epinephrine

Catecholamine with strong β-adrenergic effects; increases cardiac output, causes vasodilation, raises blood glucose.

Norepinephrine

Catecholamine with predominant α-adrenergic effects; raises blood pressure, dilates pupils, causes piloerection.

Fight-or-Flight Response

Rapid physiologic reaction mediated by SNS and catecholamines to confront or escape a threat.

Corticotropin-Releasing Hormone (CRH)

Hypothalamic hormone that initiates HPA activation by stimulating ACTH release.

Adrenocorticotropic Hormone (ACTH)

Anterior pituitary hormone that prompts the adrenal cortex to secrete cortisol.

Cortisol

Primary glucocorticoid; elevates glucose, modulates immune response, and maintains vascular tone during stress.

Acute Cortisol Effects

Gluconeogenesis, vascular tone maintenance, anti-inflammatory action, protein catabolism outside liver.

Chronic Cortisol Effects

Metabolic syndrome, central obesity, hypertension, diabetes, bone loss, poor wound healing.

Growth Hormone (GH)

Hormone that counters insulin, supports tissue repair, and affects macronutrient metabolism during stress.

Antidiuretic Hormone (ADH)

Posterior pituitary hormone that increases water reabsorption to expand circulating volume in stress.

Aldosterone

Mineralocorticoid that promotes sodium and water retention via the renin–angiotensin system.

Proinflammatory Cytokines

Immune mediators (e.g., IL-1, IL-6, TNF-α) whose levels rise with stress, linking stress to inflammation.

Th1 to Th2 Shift

Stress-induced immune change: decreased cellular (Th1) and increased humoral (Th2) immunity, predisposing to infection and autoimmunity.

Metabolic Syndrome

Cluster of conditions (abdominal obesity, dyslipidemia, hypertension, hyperglycemia) promoted by chronic cortisol elevation.

Telomere Erosion

Accelerated shortening of chromosome ends associated with early-life stress and advanced biological aging.

Adaptive Behavior

Healthy stress response strategies that restore homeostasis without long-term harm.

Maladaptive Behavior

Ineffective coping that enhances allostatic load and disease risk.

Stress-Related Diseases

Conditions such as CAD, hypertension, ulcers, asthma, depression linked to chronic stress physiology.

Third-Spacing

Extracellular fluid shift caused by increased capillary permeability during stress, leading to edema.

Platelet Aggregation (in stress)

Stress-induced increase in clotting tendency, raising risk for thrombosis and microemboli.