Pain in animals

Question 1

Define pain?

Answer 1

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

Question 2

Define noxious stimulus?

Answer 2

A stimulus that actually or potentially damages tissue, or is of quality or intensity to trigger nociceptive reactions

Question 3

Define pain threshold?

Answer 3

The least amount of pain that a subject can recognise.

Relatively constant among species and individuals

Question 4

Define pain tolerance?

Answer 4

Greatest level of pain that a subject will tolerate.

Varies considerably

Question 5

Define nociception

Answer 5

Neurophysiological term denoting specific activity in nerve pathways.
The transmission mechanism for physiological pain

Question 6

Characterise acute pain

Answer 6

Arises quickly
Can be severe
Short duration
Often fast and sharp, followed by aching pain
Centralised in one area, before becoming spread out
Responds well to medications

Question 7

Characterise chronic pain

Answer 7

Pain persisting for longer than is associated with the particular injury.
A constant or intermittent pain that has outlived its purpose
Often more difficult to treat
Often caused by improper treatment of acute pain

Question 8

Classifications of physical pain

Answer 8

1. Cutaneous
2. Somatic
3. Visceral
4. Phantom limb
5. Neuropathic
6. Central

Question 9

Describe cutaneous

• Caused by
• Nociceptors
• Aetiology

Answer 9

Caused by injury to skin or superficial tissue
Cutaneoud nociceptors, terminating just below the skin
From things such as paper cuts, first degree burns and lacerations

Question 10

Describe somatic pain

• Originates from
• Nociceptors
• Aetiology

Answer 10

Originates from ligaments, tendons, bones, blood vessels and nerves
Nociceptors - somatic, causing diffuse and prolonged pain
Aetiology - sprains and broken bones

Question 11

Describe visceral pain

• Originates from
• Nociceptors
• Aetiology

Answer 11

Originates from organs
Nociceptors - visceral (i.e. within the organs or internal cavities) causing prolonged and diffuse pain
Aetiology - myocardial ischaemia

Question 12

Describe phantom limb

Answer 12

Sensation of pain from a limb that has been lost. e.g. in amputees

Question 13

Describe neuropathic pain

Answer 13

Due to injury of the nerve tissue itself.
Causes prolonged burning pain, allodynia, hyperpathia
Often combined with vasomotor dysfunction

Question 14

Define allodynia

Answer 14

Pain caused by a stimulus that does not normally evoke a response

Question 15

What causes central pain?

Answer 15

CNS lesions

Question 16

Physiological processes of pain

Answer 16

1. transduction
2. transmission
3. modulation
4. integration

Question 17

Transduction of pain

Answer 17

When the noxious stimuli is converted into an electrical signal by nociceptors

• alpha-delta
• c-polymodal
• visceral

Question 18

Transmission of pain

Answer 18

1. Afferent sensory fibres
2. spinal cord
3. synapse with 2nd order neurones
4. ascending neurones in thalamus
5. brainstem
6. somatosensory cortex

Question 19

Modulation of pain

Answer 19

Using neurotransmitters such as:

• glutamate and asparate
• COX, prostaglandins

Question 20

Integration of pain

Answer 20

Electrochemical events combined with the unique psychology of the individual
Determines how they perceive the pain

Question 21

Describe the phenomenon of “wind up”

Answer 21

Repetitive noxious stimulation results in a change of dorsal horn cells.
Reactivity progressively increases, due to a decrease in the response threshold, resulting in hypersensitivity

Question 22

Variables affecting pain dynamic?

Answer 22

Age of animal
Species
Tissue type
Pre-existance of pain

Question 23

Physiological changes induced by pain

Answer 23

Hyperventilation
Increased cardiac output, blood pressure, and oxygen consumption
Increased blood glucose 
Increased temperature 
Increased clotting time and platelet aggregation
Vasoconstriction - ischaemia
Renal failure 
SHOCK