Pathophysiology Of Pain Flashcards
IASP definition of pain -
Unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
Transmission: sensory neurones
A delta fibres -
Nociceptors
Small/medium diameter and myelinated
Fast pain - conduction=150m/s
Transmission: sensory neurones
C fibres -
Nociceptors
Small diameter and non-myelinated therefore slow pain - 1m/s
Transmission: sensory neurones
A beta fibres -
Mechanoreceptors
Large diameter and myelinated
Mechanical stimuli, heat or cold
Describe the pain pathway -
What neurotransmitters are present?
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
What roles do these parts of the brain play in registering pain?
Thalamus -
Limbic system -
Somatosensory cortex -
Thalamus - sorting office
Limbic system - emotional and behavioural responses to pain
Somatosensory cortex - sensation experienced as pain
What is the purpose of a reflex?
To protect us from harm when there isn’t enough time to transmit info to brain and await a response
Spinal reflex/response, speed and what it’s inhibited by -
(Simple) rapid and involuntary. Inhibited by muscles/glands
Stages of the spinal reflex
1) sensory receptor -
2) sensory neurone -
1) sensory receptor responds to stimulus by producing generator/receptor potential
2) axon conducts impulses from receptor to integrating centre
Stages of spinal reflex
3) integrating centre -
4) motor neurone -
5) effector -
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
Where does the pain gate theory take place?
Takes place in dorsal horn of the spinal cord
Modulation - pain gate theory
Ascending fibres -
‘Rub it better’
AB fibres inhibit pain transmission
Modulation - pain gate theory
Descending inhibition -
Mind over matter
Mid-brain, axons descend to posterior horn of spinal cord and directly inhibit pain transmission
Pain gate is affected by:
Other impulses - (a beta activated/when a delta and C fibres are activated) -
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.
Pain gate is affected by
State of mind -
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
Pain gate is affected by
Endorphins -
Pain impulses to brain cause messages to increase endorphin release from posterior horn and Substantia gelatinosa in spinal cord. Act to close gate
Pain gate is affected by
Central control -
Brain can affect gate as a response to memories/past experience/previous response strategies
All can happen separately or at the same time
What are the different types of pain?
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
What is chronic/persistent pain?
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
Explain the biopsychosocial approach to understand health
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
Biopsychosocial approach
What are red flags? Examples -
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
Biosychosocial approach
name the yellow flags -
Attitudes and beliefs
Behaviours
Compensation issues
Diagnosis and treatment
Emotions
Family
Work - blue flags
All of these will influence individuals experience with pain
Psychological factors that can influence pain
Fear avoidance -
Catastrophising -
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’
Psychological factors that can influence pain
Pain behaviours -
Pain behaviours - guarding, rubbing, sighing and bracing
Can observe these and make links to potential severity
Cognitive functional and behavioural therapy -
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.
Name some thins that affect pain -
Age
Experiences
Distraction
Time of the day
Anticipation
Presence of existing illness
Adrenaline
Substances
Past trauma
Stress and depression/anxiety - KEY ONES
