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BVetMed - Animal Welfare > Stress > Flashcards

Stress Flashcards

1
Q

Define a stressor

A

Anything that disrupts physiological balance

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2
Q

Define the stress response

A

Biological response triggered by the body to re-establish the balance (following an actual or perceived threat)

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3
Q

Define distress

A

A biological state where the stress response has a deleterious effect upon the individuals welfare

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4
Q

What are the 4 main categories of stressor?

A
  1. Enviromental - temperature extremes, noise/vibration, famine/drought, smell
  2. Physiological - wounds, disease/infection, injury(castration/dehorning/tail docking)
  3. Social - dominancy disputes (fighting/subordination), solitary confinement
  4. Pyschological - restraint, lack of control, anxiety/fear
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5
Q

What did Walter Cannon study in 1900s? Who else investigated stress physiology after him?

A

Homeostasis
Role of adrenaline in stress physiology
Fight or flight response
Hans Selye 1950s - role of GCs in stress physiology, general adaptation syndrome

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6
Q

What was discovered about the stress response?

A

It is NON-SPECIFIC

- Selye discovered that application of a wide variety of stressors -> peptic ulcers, ^adrenal glands, v immune system

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7
Q

Other than negative stimuli, what may cause a stress response?

A

Positive experiences like playing, mating

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8
Q

Give Chrousos (1998) definition of the homeostatic concept of stress

A

“Stress is the recognition by the body of a stressor and threatened state of homeostasis, adaptive responses are the body’s attempt to counteract the stressor and re-establish homeostasis”

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9
Q

What are the problems associated with homeostatic concept of stress?

A
  • individual differences in stressor perception
  • pyschological stressors (eg. public speaking/claustrophobia)
  • ^GC/SNS triggered by pleasure too
  • Optimum homeostatic parameters shift (eg. running v sleep)
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10
Q

Give an alternative definition of stress to Chrousos (1998) definition

A

Kim and DIamond 2002 - “A condition in which individuals are aroused by aversive stimuli - the extent of the stress is determined by the individuals perception of control over the aversive stimuli

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11
Q

What are the 3 stages of the adaptive stress response?

A
  1. Recognition - appriasal and interpretation based on previous experience
  2. Biological response - defence eg. behavioural change
  3. Return of biological function to baseline
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12
Q

What may modify the adaptive stress response?

A

Modifiers

  • experience
  • genetics
  • social relationships
  • age
  • health
  • control
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13
Q

What are the two main components of the biological response?

A
  1. SAM axis
    - Catecholamines (mainly NA) from SNS
    - Catecholamines (mainly A) from adrenal medulla
    > Latency: Seconds
  2. HPA axis
    - GCs from adrenal cortex
    > Latency: Minutes
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14
Q

What are the 2 types of corticosterone receptor?

A 
Type 1 - MR
- high affinity 
- activated by low GC
- Homeostasis
Type 2 - GR 
- low affinity 
-  only activated by high GC
- Stress, abnormal behaviour
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15
Q

What is the evolutionary advantage to the stress response?

A

When activated in response to a real threat, rediverts resources from non-essential energy expensive processes to those that promote immediate survival (eg. muscles/brain) - HIGJLY ADAPTIVE
- system deactivates once crisis is averted

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16
Q

Give 6 physiological actions of the stress response

A
  1. ^energy availability and blood glucose
    - v insulin secretion -> ^ glucagon production
    - ^ gluconeogensis (GC/A/NA,) ^ lipolysis (GC) - mobilisation from existing stores
  2. ^O2 availability
    - ^resp rate (A/NA)
  3. ^blood flow to muscles
    - ^HR (A/NA)
    - ^BP (A/NA)
    - ^Blood Volume (ADH)
  4. v Pain perception (“SIA”)
    - endorphins
  5. Inhibition of non-survival systems
    - v Digestion (A/NA)
    - v growth (GC)
    - v immune function (GC) - v inflam and Ab production but migration of some immune cells to the skin surface
    - v reproduction (PRL)
  6. Enhanced alertness/sensory function/memory
    - (A/NA/ADH)
17
Q

Why does sustained stress cause pathological states?

A

Sustianed stress due to frequent activation/un-terminated stress responses/activatino due to psychological/social stress -> habituation of stressor, adaptation to deal with stressor -> exhaustion and ^ likelihood of disease.
Novel stressor will still initiate a normal stress response.

18
Q

Who discovered the “general adaption syndrome”? Outline the 3 stages.

A

Selye 1936 - Rats housed at low temperatures

  1. [2 days] Alarm reaction - ^adrenal cortex, veasinophil, altrphy of thymus/spleen/lymph
  2. [2 weeks] Resistance - no symptoms, cold adapted
  3. [2 months] - Exhausiton - died due to 2ry infection
19
Q

Who proposed the model of animal stress with 3 layers

  • recognition of a threat to homeostasis
  • stress response
  • consequences of stress (“distress/pathological state”)
A

Moberg 2000

20
Q

What are the consequences of chronic stress? What is the main cause of these?

A

= GCs usual cause
> Metabolic system
- energy mobilised constantly
- inefficient lypolsis and gluconeogenesis
- hyperglyceamia -> diabetes
- weakness/fatigue
- myopathy
> CV system
- ^ CV tone
- myocardial damage
- hypertension
- atheroscelrosis -> stroke/heart disease
> GIT
- inhibited -> loss of appetite, weight loss
- gastric ulcers
> Wound healing and immune system inhibited
- ^risk of infection/parasitism/AI disease
> Repro system inhibited
- Anovulation/lack of behavioural oestrus
- v Testosterone/impotency
- Loss of libido
> Growth inhibited
- weight loss/stunted growth
- ^ risk of fractures and osteoporosis
> Brain
- altered cognition and sensory thresholds
- hippocampal damage and cognitive impairment

21
Q

When may some of the usual signs of chronic stress not be seen?

A

Highly prolific bred farm animals may not show reproduction related problems

22
Q

How may subclinical stress cause problems?

A

Multiple sub-clinical stressors “combine” and cause pathological stress
- Animals kept in captivity and wild animals in degraded habitats particularly vulnerable to subclinical stress

23
Q

Give 2 examples of sub clinical stress causing problems.

A
  1. Wild freshwater fish populations
    - low oxygen levels -> no obvious clinical signs
    - low level toxin -> no obvious clinical signs
    > if exposed to both concurrently -> “unexplained” mortality
  2. pigs sensitive to sequential aversive stimuli
    - aggressive challenges by pen mates, tail bitten, transferred to sick pen roughly, loaded onto truck fro transport -> stress levels elevate each time until unacceptable -> collapse and death
24
Q

What do Broom and Johnson (1993) argue?

A

“Stress overtaxes control systems to the point where fitness is reduced”
- BUT this exemts many stimuli generally considered stressful
> stress implies poor welfare but poor welfare can exist without stress

25
Q

Who developed the idea of an allostatic load?

A

McEwan and Wingfield 2003

26
Q

Define allostasis

A

Achieving stability through physiological or behavioural change eg. alteration in baseline reap rate/HR/metabolism

  • sleeping/walking
  • neonate/adult
  • pregnant/non-pregnant
  • summer/winter
27
Q

Define an allostatic state

A

Entered when regulatory system operates at an altered level in response to environmental challenge or change

28
Q

Define allostatic load

A

Cumulative costs incurred by the body during allostasis

29
Q

Define allostatic overload

A

Demand exceeds capacity to cope (-ve energy balance)

  • > emergency life history stage
    eg. birds laying eggs - would normally find more food and deal with allostatic load, but if food is scarce -> overload
30
Q

What are the 2 ways of measuring stress?

A

Behaviour

Physiological measures

31
Q

What behavioural measures can be used to identify stress?

A
  • Change in behaviour
  • Detrimental behaviour eg. feather plucking/self harm
  • Stereotypies
  • Indicators of pain
32
Q

What physiological measures can be taken to identify stress?

A

> HR
- ^ emotional response (SNS)
- v freeze response (PNS)
- Arryhthmias
- Changes in HR during stressor exposure
BP ^ with chronic stress
Resp rate ^ with chronic stress
Body temp ^ core, v peripheral (SNS and adrenal cortex activity)
Immune system function
- WBCs eg. H:L ratio
- Ab production following Ag challenge v with stress
Adrenal hormones (acute stress)
- SAM (catecholamines released v quickly and metabolised v quickly)
- HPA (collect blood <5mins or urine/saliva GC later)

33
Q

How may the HPA axis be investigated to look at chronic stress?

A 
Sensitisation and desensitisation 
- chronic stress -> 
> ^GC (normal stress response)
> ^^^GC (sensitisation)
> baseline GC (habituation) 
> baseline, but novel stressor -> ^^^GC (sensitisation)
34
Q

Give examples where ^ plasma GC have been found

A
  • pigs in high stocking densities
  • calves in crates
  • dairy cattle subjected to social mixing/overcrowding
  • sows that lost aggressive encounters
35
Q

What are the problems associated with measuring stress?

A
  • no single measure will apply to all stressors
  • SAM/HPA can be activated by non-stressors
  • sample methodology can confound results by being stressful
  • Diurnal cycle of GC secretion
  • Interbreed differences in GC response eg. chickens may be flighty or calm but HR^ same
  • Inter-individual response influenced by modifiers (eg. coping system when confronted may differ between dogs, still equally stressed)
36
Q

Give 3 examples of the effects of prenatal stress

A

Lay 1997 - cattle transport stress -> ^GC and ^HR at 150d restraint test
Clarke 1994 - rhesus monkeys stress -> v birth weight, developmental delay, attentional deficit, v social behaviour, v cognition, ^ stress responsiveness
Levine 1967 - rats stress -> v emotional response to novelty and v HPA response to stress

37
Q

What did Liu 1997 investigate?

A

Epigenetics of rat rearing - if raised by calm, nurturing mother -> calm, nurturing adult
If raised by anxious, non-nurtering mother -> anxious, non nurturing adult
> ^Type 2 corticosterone receptors due to ^ licking

38
Q

How does predictability affect stress responsiveness? Outline a study.

A

If stimuli are predictable and of constant intensity -> Habituation
If stimuli are unpredictable or of varying intensity -> Anxiety as animal cannot prepare or predict the next stimulus
eg. Weiss 1972 - rats given random or predictable (light cue) shocks
> random group - ^GC, stomach ulcers, disrupted immune system due to ^ anxiety
> control group knew they were safe when light wasn’t on

BVetMed - Animal Welfare (19 decks)

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