Medical-Surgical Nursing · Stress and Stress-Related Disorders
Physiological Response
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In 30 seconds
When the brain perceives a threat — a near-miss on the highway, an unexpected diagnosis — the body reacts within seconds, long before conscious thought catches up. This is the physiological stress response, a coordinated set of changes driven by two overlapping systems: the fast-acting Sympathetic nervous system The branch of the autonomic nervous system that activates the body for action Full entry → and the slower HPA axis Hypothalamus → pituitary → adrenal cortex hormone chain Full entry → (hypothalamus → pituitary → adrenal glands).
This topic walks through what happens in the body during stress: which hormones are released, what they do to the heart, lungs, blood vessels, metabolism, and immune system, and how the response is supposed to switch off. It also covers the General adaptation syndrome Selye's three-phase model: alarm, resistance, exhaustion Full entry → (GAS), the three-phase model (alarm, resistance, exhaustion) that explains what happens when stress is brief, prolonged, or overwhelming. For the nurse, this turns "the patient is stressed" from a vague impression into specific observations: elevated heart rate and blood pressure, rapid breathing, restlessness, and — when stress continues — sleep disturbance and fatigue.
Why this matters
- Recognizing the stress response: Many "abnormal" vital signs are actually a normal stress response to hospitalization itself. A patient anxious about surgery may have an elevated heart rate and blood pressure that improve with explanation and reassurance.
- Understanding the body's limits: The difference between a brief, adaptive response and prolonged activation explains why chronic stress is associated with problems like persistent hypertension, impaired sleep, and altered glucose handling.
- Safe assessment: The same physical signs (fast heart rate, elevated blood pressure, rapid breathing) can reflect stress, pain, fever, hypoxia, medication effects, or a worsening condition. The nurse must consider all of them — never assume a change is "just stress."
- Patient education: Explaining to a patient why their heart is racing ("your body's alarm system is on; here's what we can do") is itself a nursing intervention that can reduce distress.
The college version
Core Concepts
The fast system: sympathetic-adrenal-medullary (SAM) axis
When the brain detects a threat, the sympathetic nervous system fires, and the adrenal medulla releases epinephrine and norepinephrine (Catecholamines Epinephrine and norepinephrine, released by the adrenal medulla Full entry →). Within seconds, these hormones produce the classic Fight-or-flight The set of immediate body changes preparing to confront or escape a threat Full entry → changes:
- Heart rate and the force of contraction increase; blood pressure rises.
- Airways open and breathing quickens, delivering more oxygen.
- Blood flow shifts away from the skin and digestive tract toward skeletal muscle and the heart.
- Pupils dilate, and blood glucose rises to fuel the muscles.
These changes are adaptive for a genuine emergency: they prepare the body to fight or flee. The parasympathetic system is the counterweight that restores calm afterward.
The slower system: HPA axis and cortisol
If the threat lasts beyond the first minutes, the hypothalamus releases corticotropin-releasing hormone (CRH), which signals the pituitary to release adrenocorticotropic hormone (ACTH), which triggers the adrenal cortex to release Cortisol A glucocorticoid that sustains blood glucose, blood pressure, and immune modulation during stress Full entry →, a glucocorticoid. Cortisol works over minutes to hours:
- It helps maintain blood glucose by promoting the release of stored glucose.
- It modulates the immune system and suppresses inflammation.
- It supports blood pressure and helps the body sustain a prolonged response.
Cortisol is essential for life — people with adrenal insufficiency cannot mount this response. The problem is not cortisol itself; it is cortisol and catecholamines circulating too often and for too long.
General adaptation syndrome (GAS)
Hans Selye's classic model describes the body's response in three phases:
- Alarm: The threat is detected; the SAM and HPA axes activate. The person feels the surge — racing heart, quick breathing, heightened alertness.
- Resistance: If the stressor continues, the body tries to adapt and keep functioning; hormone levels may stay elevated even though the person no longer feels alarmed. This phase is costly: energy is diverted from digestion, growth, and repair.
- Exhaustion: If the stressor outlasts the body's resources, adaptive capacity fails. The person experiences fatigue, impaired immunity, and increased vulnerability to illness.
GAS is a useful framework, not a law: real stressors do not always march neatly through the phases, and individual responses vary widely.
Effects across body systems
A single stress episode is a coordinated whole-body event; prolonged stress leaves fingerprints on several systems:
- Cardiovascular: repeated elevation of heart rate and blood pressure; over time this pattern is associated with cardiovascular risk (effects vary by person).
- Metabolic: stress hormones raise blood glucose; in people with diabetes, stress can make glucose control more difficult.
- Immune: short-term stress can enhance some immune responses; chronic stress is associated with altered immune function and slower healing.
- Gastrointestinal: blood flow shifts away from the gut during stress; patients often report nausea, heartburn, or appetite change.
- Sleep and recovery: elevated stress hormones interfere with restful sleep, and poor sleep amplifies the stress response — a vicious cycle.
Nursing assessment of the stress response
Observe and document what is measurable: heart rate, blood pressure, respiratory rate, pupil size, skin color and moisture, muscle tension, restlessness, and sleep patterns. Ask about the patient's perception of their stress. Vital signs are context-dependent: the same heart rate can mean anxiety in one patient and compensated shock in another. Compare with baseline, consider pain and other causes, and report changes that persist or worsen.
Common Confusions
| Do not confuse | With | Difference |
|---|---|---|
| Epinephrine | Cortisol | Epinephrine acts in seconds (fight-or-flight); cortisol acts over minutes to hours (sustained response) |
| Sympathetic activation | Parasympathetic activation | Sympathetic speeds the body up; parasympathetic calms it down and restores rest |
| Stress response | Stress-related illness | The response is normal physiology; illness arises when activation is excessive or prolonged |
| Elevated vital signs from stress | Elevated vital signs from a physical cause | The signs are identical — the nurse must assess for both before concluding |
| "The body gets exhausted" (GAS) | Adrenal failure | GAS exhaustion describes running out of adaptive capacity; adrenal insufficiency is a specific medical diagnosis |
| One stress hormone | A coordinated system | Many hormones and nerves work together; "cortisol only" is an oversimplification |
Eli explains
The same idea, in plain words
Explain it like I’m 10
Your body has a built-in alarm system. If a dog chases you, the alarm shouts "RUN!" — your heart beats faster, you breathe harder, and your legs get extra energy, all in a few seconds. That's the fast alarm (the "fight-or-flight" system). If the danger doesn't go away, a second, slower alarm sends out a chemical called cortisol to keep you going for a while. The alarms are great for real emergencies — but if they never turn off, your body gets tired and worn down, like a smoke detector that beeps all night long.
Worked example
Ms. Rivera, age 34, is admitted for an elective procedure tomorrow morning. The night nurse finds her heart rate at 108 and blood pressure elevated, and she is restless, with cool, slightly damp hands. The nurse considers the possibilities: pain? fever? dehydration? medication effect? hypoxia? The nurse checks oxygen saturation, temperature, and pain score — all unremarkable. Then the nurse sits down and asks, "How are you feeling about tomorrow?" Ms. Rivera admits she has never had surgery and is terrified something will go wrong.
The nurse explains what to expect step by step, teaches a simple slow-breathing technique, and offers to page the provider if her symptoms persist. After 20 minutes of calm conversation and breathing, her heart rate is 92. The nurse documents the assessment, the teaching, and the improvement, and notes that her baseline anxiety should be communicated to the day-shift team. She did not "diagnose anxiety" or dismiss the elevated vital signs; she ruled out physical causes, addressed the stressor, and documented the whole picture.
Key takeaways
- Two systems drive the stress response: the SAM axis (fast, catecholamines → fight-or-flight) and the HPA axis (slower, CRH → ACTH → cortisol).
- Epinephrine/norepinephrine act in seconds; cortisol acts over minutes to hours and helps sustain the response.
- General adaptation syndrome: alarm → resistance → exhaustion; exhaustion is when adaptive capacity runs out.
- The stress response is adaptive in short bursts and costly when prolonged (allostatic load).
- Stress hormones raise heart rate, blood pressure, respiratory rate, and blood glucose — all of which are also signs of other problems.
- Never label a change in vital signs "just stress" without checking pain, fever, hypoxia, medications, and the patient's baseline.
- The nurse's interventions: calm environment, explanation, slow-breathing coaching, addressing pain and fears — plus reporting persistent findings to the provider.
Check yourself
5 review questions from the chapter. Try each one, then open the answer.
Name the two major systems of the physiological stress response and the key hormones each releases.
Show answer
The SAM axis (sympathetic nervous system + adrenal medulla, releasing epinephrine and norepinephrine) and the HPA axis (hypothalamus → CRH → pituitary → ACTH → adrenal cortex → cortisol).
List four immediate fight-or-flight changes a nurse might observe.
Show answer
Increased heart rate and contractility, elevated blood pressure, faster breathing and dilated airways, dilated pupils, blood flow shifted from skin/gut to muscles, and rising blood glucose (any four).
What are the three phases of the general adaptation syndrome, and what characterizes each?
Show answer
Alarm (threat detected, stress axes activated, the "surge" of symptoms), resistance (body adapts and keeps functioning while hormone levels may stay elevated), and exhaustion (adaptive capacity runs out; fatigue, impaired immunity, increased vulnerability to illness).
Why is a prolonged stress response harmful even though the acute response is protective?
Show answer
Because the response is designed for brief emergencies; when it fires repeatedly or continuously, the same hormones that are protective in short bursts contribute to wear and tear (allostatic load) — affecting cardiovascular, metabolic, immune, GI, and sleep function.
A patient's heart rate and blood pressure are elevated. What must the nurse consider before attributing this to stress?
Show answer
Pain, fever, hypoxia, dehydration, medication effects, anxiety/fear, the patient's baseline, and the possibility of a worsening underlying condition — stress is one possibility, never the automatic conclusion.
Study tools & related lessonsKey vocabulary · Related
Key vocabulary
- Sympathetic nervous system
- The branch of the autonomic nervous system that activates the body for action
- Catecholamines
- Epinephrine and norepinephrine, released by the adrenal medulla
- HPA axis
- Hypothalamus → pituitary → adrenal cortex hormone chain
- Cortisol
- A glucocorticoid that sustains blood glucose, blood pressure, and immune modulation during stress
- General adaptation syndrome
- Selye's three-phase model: alarm, resistance, exhaustion
- Fight-or-flight
- The set of immediate body changes preparing to confront or escape a threat
Sources & references
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