Stress/Selye's Concept Flashcards
Who first described the concept of stress?
Hans Selye in 1930’s
“Specific neural, endocrine and immune effect upon exposure to noxious stimuli/pathogens”
What did Dantzer and Mormede suggest about stress in 1983?
“Environmental stressors exert their noxious effects not only through their physical qualities but through their psychological effects on the animal”
What determines the impact of stress on an organism? (9)
- Number
- Intensity
- Duration
- Transient vs chronic
- Temporal juxtaposition
- Interaction
- Age
- Experience/history/genetics
- Perception
- Adaptation
What are two types of stress?
Eustress (positive)
Distress (negative)
- Any all changes initiate stress which is not always detrimental
- Stress is context dependent : occurs when an individuals context is altered
- Psychological/physiological stress is unavoidable in life
What must happen in response to stress?
The organism must respond by adapting to the change
How does an organism adapt to stress?
Adaptation begins with activation of systems designed to maintain homeostasis
- Nervous, endocrine, immune
What is the result of a failure to adapt?
- Over-activity or inactivity of psychological systems
- increases wear and tear on body and brain
- Homeostasis perturbed chronically - internal state defining health is jeopardized
What are three behavioural responses to stress?
- Avoidance
- Displacement
- eg biting nails
- Reflexes
- eg pulling hand away from heat
What are 7 Neuro-endocrine responses to stress?
- Sympathetic vs Parasympathetic
- Hypothalamus (CRH, GnRH)
- Pituitary (GH, Prl, LH, TSH, ACTH)
- Adrenal (Aldosterone, NE, E, Cortisol)
- Thyroid (T3 and T4)
- Pancreas (insulin, glucose)
- Gonads (sex hormones)
HPA Axis is very important
What are 6 early behavioural responses/adaptations to stress?
(lion/zebra example)
- Altered cognition & attention span - facilitate adaptive neural pathways for coping
- Increased alertness
- Altered sensory threshold
- Sharpened memory and sensation
- Stress-induced analgesia
- Suppression of feeding behaviour
- Suppression of Reproductive behaviour
What are four early physiological responses and adaptations to stress?
- Oxygen and nutrients redirected to CNS and stressed body sites (muscle/lungs/heart)
- Rapid detoxification from toxic products (liver)
- Altered cardiovascular tone
- increased hr, co, stroke volume
- vasodilation of vessels in muscle
- vasoconstriction of vessels in gut
- Containment of the stress response
- stress response is only beneficial in Short-Term
Changes in which gland are thought to be critical adaptations to stress?
Changes in adrenal activity (Adrenocortical response)
What are 3 types of physical stress known to modulate cortisol secretion by the adrenal gland?
- Hypoglycemia (glucose regulation)
- Trauma
- broken bones
- burns
- surgery
- cold exposure
- infection
- Heavy exercise
What are 2 psychological stressors that are known to increase cortisol secretion by the adrenal gland?
- Acute anxiety
- anticipation of stressful situations
- novel situations
- Chronic anxiety
What is Selye’s definition of the stress response?
Stress is the sum of all non-specifici systemic reactions of the body which ensue upon long-term exposure to stress
- stressors of all different kinds elicit same response
What were four results Selye observed in his rats (both experimental group and control group) after his experiment to observe a novel ovarian hormone?
From rats in both groups:
- Discovered physiological/tissue changes that occur with stress
- peptic ulcers/atrophied immune tissue etc
- Changes in blood electrolytes (Na+/K+), glucose, lipids, blood pressure, blood clotting time
- Dramatic endocrine and immune cell changes
- hyperplasia of adrenal glands (enlarged adrenals)
What are the three phases of the stress response? ie Selye’s “General Adaptation Syndrome”
- “Alarm” reaction
- Initial mobilization of the bodys defenses
- Further sub-divided into
- Shock-reaction phase
- initial response to offensive stimuli
- Counter-shock reaction phase
- systemic redistribution of resources to counteract, neutralize or overcome the challenge at hand
- Shock-reaction phase
- Resistance/Adaptation Phase
- Initiated if the challenge persists
- Body systems handle the offending condition well, maintain stability
- Exhaustion phase
- If noxious stimuli does not abate
- Attempts to hold the challenge in check cease
- Potentially leads to death
What happens during the first (Alarm Reaction) phase of the stress response? Subdivisions?
“Alarm” reaction
- Initial mobilization of the bodys defenses
- Further sub-divided into:
-
Shock-reaction phase
- initial response to offensive stimuli
-
Counter-shock reaction phase
- systemic redistribution of resources to counteract, neutralize or overcome the challenge at hand
-
Shock-reaction phase
What happens during the second phase of the stress response (Resistance/Adaptation phase)?
Resistance/Adaptation Phase
- Initiated if the challenge persists
- Body systems handle the offending condition well, maintain stability
What happens during the third phase of the stress response (Exhaustion Phase)?
Exhaustion phase
- If noxious stimuli does not abate
- Attempts to hold the challenge in check cease
- Potentially leads to death
What is the General Adaptation Syndrome (GAS)
Stressor -> Adrenals release adrenomedullary hormones (eg Norepinephrine) which triggers:
- Alarm:
- Body reacts to the stressor
- HPA axis
- Symphatetic NS
- Adaptation
- Sustained release of cortisol from adrenals in an attempt to maintain arousal
- Adaptation to stress
- a) if SUCCESSFUL ADAPTATION
* homeostasis is restored - b) FAILED ADAPTATION
-
exhaustion phase
- resources are depleted
- disease/death
