Pathophysiology Of Pain

Question 1

IASP definition of pain -

Answer 1

Unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

Question 2

Transmission: sensory neurones
A delta fibres -

Answer 2

Nociceptors
Small/medium diameter and myelinated
Fast pain - conduction=150m/s

Question 3

Transmission: sensory neurones
C fibres -

Answer 3

Nociceptors
Small diameter and non-myelinated therefore slow pain - 1m/s

Question 4

Transmission: sensory neurones
A beta fibres -

Answer 4

Mechanoreceptors
Large diameter and myelinated
Mechanical stimuli, heat or cold

Question 5

Describe the pain pathway -
What neurotransmitters are present?

Answer 5

Stimulus - AP will travel via sensory/afferent nerve
AP can either go down dorsal or ventral column
Sensory is always dorsal column
AP up spinal cord and goes to thalamus (thalamus relays motor/sensory signals to whole cerebral cortex)
Then travels via synapse to 3rd order neurone to find region of the brain for particular injured bodily cite. Therefore brain will recognise pain

Neurotransmitters - glutamate and substance P all AP’s to pass for 1st-2nd-3rd order neurone

Question 6

What roles do these parts of the brain play in registering pain?
Thalamus -
Limbic system -
Somatosensory cortex -

Answer 6

Thalamus - sorting office
Limbic system - emotional and behavioural responses to pain
Somatosensory cortex - sensation experienced as pain

Question 7

What is the purpose of a reflex?

Answer 7

To protect us from harm when there isn’t enough time to transmit info to brain and await a response

Question 8

Spinal reflex/response, speed and what it’s inhibited by -

Answer 8

(Simple) rapid and involuntary. Inhibited by muscles/glands

Question 9

Stages of the spinal reflex
1) sensory receptor -
2) sensory neurone -

Answer 9

1) sensory receptor responds to stimulus by producing generator/receptor potential

2) axon conducts impulses from receptor to integrating centre

Question 10

Stages of spinal reflex
3) integrating centre -
4) motor neurone -
5) effector -

Answer 10

3) integrating centre is one/more reigons within CNS that relay impulses from sensory to motor neurone
4) axon conducts impulses from integrating centre to effector
5) muscle/gland responds to motor nerve impulses

Question 11

Where does the pain gate theory take place?

Answer 11

Takes place in dorsal horn of the spinal cord

Question 12

Modulation - pain gate theory
Ascending fibres -

Answer 12

‘Rub it better’
AB fibres inhibit pain transmission

Question 13

Modulation - pain gate theory
Descending inhibition -

Answer 13

Mind over matter
Mid-brain, axons descend to posterior horn of spinal cord and directly inhibit pain transmission

Question 14

Pain gate is affected by:
Other impulses - (a beta activated/when a delta and C fibres are activated) -

Answer 14

If no stimulus, gate is closed
If A beta fibres activated eg by pressure , inhibitory interneuron is then inhibiting substance P, so gates close. Substantia gelatinousa (SG) is excited - gate is blocked/closed to pain impulses which therefore do not pass up to the brain

If A delta and C fibres activated, carry pain impulses to the gate in spinal cord. Inhibitory interneuron is inhibited, gate is open and impulses can carry the pain message to the brain.

Question 15

Pain gate is affected by
State of mind -

Answer 15

Substantia gelatinosa at pain gate will be influenced eg. Anxiety causes impulses from brain to open gate, therefore increased pain perception
Relaxed - activate SG to close gate

Question 16

Pain gate is affected by
Endorphins -

Answer 16

Pain impulses to brain cause messages to increase endorphin release from posterior horn and Substantia gelatinosa in spinal cord. Act to close gate

Question 17

Pain gate is affected by
Central control -

Answer 17

Brain can affect gate as a response to memories/past experience/previous response strategies
All can happen separately or at the same time

Question 18

What are the different types of pain?

Answer 18

Acute and persistent
Chronic
Nociceptor - mechanical stimulus or inflammation
Neuropathic pain - nerves irritation
Nociplastic pain - no specific cause but mental state keeps pain gates open

Question 19

What is chronic/persistent pain?

Answer 19

Pain lasting beyond time of healing of injury
May not be due to any clearly identifiable cause
May be due to dysfunctional nociceptive system eg hypersensitivity or on going tissue damage eg arthritis, cancer
46% population report chronic pain

Question 20

Explain the biopsychosocial approach to understand health

Answer 20

Takes all factors into account regarding health and pain
Biology - eg gender, physical illness, disability and medication effects
Social context - social support, family history, education and culture
Psychology - learning/memory, attitudes/beliefs, personality, behaviours and post trauma

Question 21

Biopsychosocial approach
What are red flags? Examples -

Answer 21

Clinical signs that may indicate serious pathology
Eg constant pain
Night pain
Cancer history
Significant weight loss
Smoking history
Put them all together may indicate cancer for eg

Question 22

Biosychosocial approach
name the yellow flags -

Answer 22

Attitudes and beliefs
Behaviours
Compensation issues
Diagnosis and treatment
Emotions
Family
Work - blue flags
All of these will influence individuals experience with pain

Question 23

Psychological factors that can influence pain
Fear avoidance -

Catastrophising -

Answer 23

Fear - leads to seeking behaviours such as avoidance/escape and hypervigilance
Constant thinking about pain and amplifying it

Catastrophising - can lead to chronic issues. Normal behaviour = hypercondria
Eg Catastrophising belief - ‘exercising hurts my back so I shoulder do it’

Question 24

Psychological factors that can influence pain
Pain behaviours -

Answer 24

Pain behaviours - guarding, rubbing, sighing and bracing
Can observe these and make links to potential severity

Question 25

Cognitive functional and behavioural therapy -

Answer 25

Looks at patient as whole picture
Change faulty movements/fucntions
Reconceptualise the pain
Train in multiple pain coping skills
Behavioural rehearsal and guided practise
CFT and CBT reduce pain and disability associated with persistent pain.

Question 26

Name some thins that affect pain -

Answer 26

Age
Experiences
Distraction
Time of the day
Anticipation
Presence of existing illness
Adrenaline
Substances
Past trauma
Stress and depression/anxiety - KEY ONES