The "fight-or-flight" response was described by Walter Cannon. Which nervous system branch drives it and what are its immediate physiological effects?
A: Parasympathetic nervous system; it produces slowed heart rate, increased digestion, and pupil constriction
B: Sympathetic nervous system; it produces increased heart rate, bronchodilation, peripheral vasoconstriction, glucose mobilisation, and inhibition of digestion
C: Enteric nervous system; it redirects blood flow from the brain to the gut to prepare for metabolic demands
D: Somatic nervous system; it increases voluntary muscle tone and prepares the body for physical combat
Correct: Sympathetic nervous system; it produces increased heart rate, bronchodilation, peripheral vasoconstriction, glucose mobilisation, and inhibition of digestion
Walter Cannon (1915) coined "fight-or-flight" to describe the coordinated sympathetic nervous system response to threat. Sympathetic activation (via preganglionic neurons in the spinal cord → postganglionic sympathetic neurons → target organs) produces: increased heart rate and cardiac output; bronchodilation (dilates airways for more oxygen); pupil dilation (mydriasis); peripheral vasoconstriction (redirects blood to muscles); liver glycogenolysis (raises blood glucose); inhibition of digestion (reduced GI motility); and piloerection (goosebumps — vestigial). Simultaneously, the adrenal medulla releases adrenaline (epinephrine) and noradrenaline into the bloodstream, amplifying and sustaining these effects hormonally. The complementary parasympathetic "rest-and-digest" response governs recovery.
Describe the HPA axis and its hormonal cascade from stress perception to cortisol release.
A: Hippocampus → ACTH → pituitary → CRH → adrenal cortex → cortisol
B: Hypothalamus (CRH) → anterior pituitary (ACTH) → adrenal cortex → cortisol
C: Amygdala (CRH) → posterior pituitary (ACTH) → adrenal medulla → cortisol
D: Prefrontal cortex → hypothalamus → adrenal cortex → CRH → cortisol
Correct: Hypothalamus (CRH) → anterior pituitary (ACTH) → adrenal cortex → cortisol
The HPA axis is the body's primary endocrine stress response system. When the amygdala and prefrontal cortex perceive a stressor and relay signals to the hypothalamus, the paraventricular nucleus (PVN) of the hypothalamus releases corticotropin-releasing hormone (CRH) into the portal circulation → anterior pituitary responds by releasing adrenocorticotropic hormone (ACTH) into the bloodstream → ACTH acts on the adrenal cortex (outer layer of the adrenal gland) → adrenal cortex synthesises and releases cortisol (a glucocorticoid). Cortisol then exerts negative feedback on the hypothalamus and pituitary, dampening further CRH and ACTH release — a self-limiting loop. The full response takes ~15–30 minutes (much slower than the immediate SAM response). Chronic stress impairs this negative feedback, leading to sustained cortisol elevation.
Cortisol has multiple effects throughout the body during stress. Which combination of effects is accurate?
A: Cortisol stimulates immune function, decreases blood glucose, and promotes fat storage
B: Cortisol mobilises energy (raises blood glucose via gluconeogenesis), suppresses the immune and inflammatory response, and enhances memory consolidation of emotionally significant events
C: Cortisol lowers blood pressure, promotes sleep, and enhances digestive function to ensure sustained energy supply
D: Cortisol exclusively affects the immune system; its metabolic effects are produced by adrenaline
Correct: Cortisol mobilises energy (raises blood glucose via gluconeogenesis), suppresses the immune and inflammatory response, and enhances memory consolidation of emotionally significant events
Cortisol is a glucocorticoid with wide-ranging effects: (1) Energy mobilisation: cortisol raises blood glucose through hepatic gluconeogenesis (producing glucose from amino acids and glycerol) and lipolysis, ensuring fuel for the stressed organism. (2) Anti-inflammatory and immunosuppressive effects: cortisol suppresses the innate and adaptive immune response via multiple mechanisms (reduced cytokine production, T-cell proliferation, and antibody production) — this is why synthetic glucocorticoids (prednisone, dexamethasone) are used for autoimmune and inflammatory conditions. (3) Memory modulation: cortisol interacts with the amygdala and hippocampus to enhance consolidation of emotionally significant memories (adaptive — remember threatening events). (4) Other effects: elevated blood pressure, reduced bone formation, impaired wound healing. Chronically elevated cortisol causes cumulative damage to these same systems.
Hans Selye's General Adaptation Syndrome (GAS) describes the body's response to prolonged stress in three stages. What are they and what happens in the exhaustion stage?
A: Awareness → resistance → recovery; exhaustion corresponds to recovery if stressor is removed in time
B: Alarm → resistance → exhaustion; in the exhaustion stage, the body's resources are depleted, physiological defences break down, and disease/death can result
C: Arousal → adaptation → homeostasis; exhaustion is reached when the body successfully adapts to the stressor
D: Fight → flight → freeze; exhaustion occurs when freezing is no longer possible and the organism surrenders
Correct: Alarm → resistance → exhaustion; in the exhaustion stage, the body's resources are depleted, physiological defences break down, and disease/death can result
Selye (1936, 1950) proposed that any sufficiently intense or prolonged stressor produces a nonspecific, three-stage physiological response — the General Adaptation Syndrome: (1) Alarm reaction: initial fight-or-flight activation (SAM axis), followed by temporary resistance decrease as the body mobilises. (2) Resistance/adaptation: the body adapts to the stressor; cortisol and other stress hormones remain elevated to maintain readiness; resistance to the specific stressor is high, but resistance to other stressors may be reduced. (3) Exhaustion: if the stressor continues long enough, physiological resources are exhausted — adrenal glands enlarge then hypertrophy, immune function collapses, peptic ulcers develop, and disease vulnerability soars. Selye's key insight was that diverse stressors (infection, cold, injury, psychological threat) produce the same physiological pattern — demonstrating a nonspecific stress response.
What is "allostatic load" (McEwen & Stellar, 1993) and why is it clinically important?
A: The total amount of stress an organism can tolerate before the fight-or-flight response is triggered; individuals with higher allostatic load are more resilient
B: The cumulative physiological wear-and-tear on body systems resulting from repeated or chronic activation of stress-response systems — associated with increased risks of cardiovascular disease, diabetes, depression, and accelerated ageing
C: The body's baseline level of cortisol maintained during non-stressful conditions; elevated allostatic load indicates healthy adaptation to chronic environmental demands
D: A measure of how quickly an individual's stress hormones return to baseline after a stressor; lower recovery rate = higher allostatic load
Correct: The cumulative physiological wear-and-tear on body systems resulting from repeated or chronic activation of stress-response systems — associated with increased risks of cardiovascular disease, diabetes, depression, and accelerated ageing
McEwen and Stellar introduced allostasis to describe how the body achieves stability through change — activating stress systems to meet demands. Allostatic load is the cumulative cost of this repeated adaptation: the physiological "weathering" that results from chronic, repeated, or inefficiently managed stress responses. High allostatic load (measured as a composite of biomarkers: cortisol, catecholamines, inflammatory markers, cardiovascular indices, BMI) is associated with accelerated biological ageing, increased risk of cardiovascular disease, type 2 diabetes, immune dysfunction, depression, cognitive decline, and early mortality. Importantly, allostatic load accumulates unevenly by socioeconomic status — chronic exposure to poverty, discrimination, and adversity produces measurably higher allostatic load across a lifetime, partly explaining health disparities.
Psychoneuroimmunology (PNI) studies the relationship between stress and immune function. What does research consistently show?
A: Brief acute stress enhances certain aspects of immune function; chronic stress suppresses immune function and increases vulnerability to infection and some cancers
B: All forms of stress — acute and chronic — uniformly suppress immune function
C: Psychological stress has no measurable effect on immune parameters; immune function is determined solely by genetics and nutrition
D: Chronic stress improves vaccine efficacy because elevated cortisol acts as an adjuvant
Correct: Brief acute stress enhances certain aspects of immune function; chronic stress suppresses immune function and increases vulnerability to infection and some cancers
Psychoneuroimmunology — pioneered by Robert Ader, Nicolas Cohen, and David Felten — has established robust bidirectional links between the nervous, endocrine, and immune systems. Key findings: (1) Acute/short-term stress can enhance certain immune functions (increased natural killer cell activity, enhanced wound healing in some protocols) — an adaptive preparation for potential injury. (2) Chronic stress consistently suppresses immune function — elevated cortisol reduces T-cell proliferation, NK cell activity, and antibody production. Cohen et al.'s controlled human studies showed that people with more life stress were significantly more likely to develop a cold after deliberate rhinovirus exposure, and the effect was dose-dependent. (3) Chronic stress also produces paradoxical proinflammatory states (via sympathetic–immune crosstalk) linked to depression, cardiovascular disease, and cancer promotion.
Shelley Taylor's "tend-and-befriend" model of stress response proposes what, and in which group was it originally described?
A: That the fight-or-flight response is the universal human stress response, equally present in all groups
B: That females tend to respond to stress by nurturing offspring ("tending") and seeking social alliances ("befriending") — driven by oxytocin and oestrogen — as an alternative to fight-or-flight
C: That children universally respond to stress by seeking adult protection, a response driven by cortisol suppressing fear
D: That highly social individuals of any gender are more likely to seek social support under stress, while less social individuals tend to fight or flee
Correct: That females tend to respond to stress by nurturing offspring ("tending") and seeking social alliances ("befriending") — driven by oxytocin and oestrogen — as an alternative to fight-or-flight
Taylor et al. (2000) proposed that much of the foundational stress research was conducted on male subjects — both animal and human — and that females may have evolved a distinct response pattern. Rather than fight-or-flight (which could be costly or dangerous for females with dependent offspring), females may respond to threat by tending (nurturing, protecting offspring) and befriending (seeking and providing social support through social networks). The biological underpinning: oxytocin (released during stress) promotes affiliative and caregiving behaviour; oestrogen amplifies oxytocin effects; progesterone further reduces anxiety. Adrenaline tends to enhance fight-or-flight, while oxytocin tends to counteract it. Human research supports that women use social support as a stress-coping strategy more frequently than men, and social support buffers stress more strongly for women on some biological measures. The model is influential but has been criticised for overgeneralising sex differences.
Richard Lazarus's transactional model of stress proposes that stress is not defined by the stressor itself but by the individual's appraisal of it. What are primary and secondary appraisal?
A: Primary appraisal = physiological response; secondary appraisal = cognitive labelling of the physiological response
B: Primary appraisal = evaluation of whether the situation is threatening, harmful, or challenging; secondary appraisal = evaluation of whether one has the resources to cope
C: Primary appraisal occurs in the amygdala automatically; secondary appraisal is the cortical override that can prevent the stress response
D: Primary appraisal = first exposure to a stressor; secondary appraisal = re-evaluation after the stressor recurs
Correct: Primary appraisal = evaluation of whether the situation is threatening, harmful, or challenging; secondary appraisal = evaluation of whether one has the resources to cope
Lazarus and Folkman's transactional model (1984) defines stress as a transaction between person and environment, mediated by cognitive appraisal. Primary appraisal is the initial evaluation: Is this situation irrelevant, benign/positive, or stressful? If stressful, is it threatening (anticipated harm), harmful (already occurred), or challenging (potential for gain through effort)? Secondary appraisal is the evaluation of coping resources: Do I have the ability, skills, social support, or resources to handle this? Stress occurs when perceived demands exceed perceived coping resources. Crucially, the same objective stressor (e.g., a public speaking task) produces vastly different physiological responses depending on appraisal — explaining why individual differences in stress reactivity can be so large. The model has been highly influential in stress management interventions: changing appraisals (cognitive reappraisal, challenge vs threat framing) can reduce the physiological stress response.
Stress Physiology
The "fight-or-flight" response was described by Walter Cannon. Which nervous system branch drives it and what are its immediate physiological effects?
About this quiz
Stress is the body's ancient response to threat — a cascade of neural and hormonal changes that mobilise resources, sharpen attention, and prepare for action. In the short term it is adaptive; chronically activated, it damages almost every system in the body.
This quiz covers the two main stress-response systems (SAM axis and HPA axis), Hans Selye's General Adaptation Syndrome, cortisol and its effects, allostatic load, and the psychological dimensions of chronic stress — from immunosuppression to Shelley Taylor's tend-and-befriend model.