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Pain
Learning Outcomes
Learning Outcomes
- Outline ways that pain can be adaptive and maladaptive
- Outline the neuron types and anatomical structures in the pain sensory pathway
- Evaluate causes, symptoms and examples of:
- Acute pain
- Chronic pain
- Neuropathic pain
- Referred pain
- Visceral pain
- Somatic pain
- Summarise Malzeck & Wall’s Pain Gate theory
- Evaluate tools for assessing pain
Physiologically, what is purpose of Pain?
Helps us protect ourselves from the outside world
Purpose of Pain: Adaptive
- Evolutionary! Alert system to possible danger
- Biological function of stopping and/or reducing further injury (e.g. congenital analgesia)
- Promotes learning to avoid future injury
- Set limits on activity forcing rest and allowing for recuperation and recovery.
Maladaptive Pain
Sensory Receptors
Sensory Receptors
Information goes into the CNS and the brain interprets it as PAIN.
It did NOT go in as pain
Receptors & Sensation they detect
Name receptors that you know
Where are they?
What do they detect?
Mechanoreceptors (mechanical movements: skin, CT, muscle)
Thermoreceptors: Temperature (skin)
Chemoreceptors: Chemistry (blood)
Nocireceptors: Position in space (muscles, joints, ligaments)
Pain is not an input
Acute:
- Is usually associated with clear injury or disease in tissues
- Physical tissue response (e.g. inflammatory response)
- If healing occurs, pain improves proportionally
- Quality: stabbing, sharp
Chronic:
- Pain that exists > 3 months
- Cause may not have resolved, or existing chronic disease (e.g. RA); however brain’s perception & interpretation of pain plays a role
- Has become more complex- less association between original cause and experience of pain
- Quality: burning, electrifying, changeable
Pain Perception
ALARM
- Nerves, immune cells & chemicals in the body send signals to the brain
INTERPRETATION
- Emotions and memory interact with these signals in the brain
PAIN
- Output from the brain, generated as the sum of all these inputs
Experience of Pain
Multifactorial
- Determined by sensitivity of your system
- NOT the amount of damage in your tissues
Yellow Flags
How might yellow flags be associated with Pain? What are they?
Discuss in groups how this might be linked to:
- Lower back pain
- Stress levels
- Poor work environment
- Lack of family support
- Recent bad health
- Recently made redundant
Types of Pain
Referred Pain
Map showing how
Visceral organs and
somatic pain fibres
are innervated by
same nerves
so brain interprets
as coming from the
more common somatic pathway
Theory of Pain
Malzeck & Wall's Theory of Pain (1965)
Medium speed Aδ (delta) fibres send pain signal to CNS
- Causes reflex withdrawal
Slow C fibres send pain signal to spinal cord & fast Aβ (beta) fibres not activated
- Inhibitory neuron not activated
- Pain signal goes through to brain
Rubbing hurt toe activates fast Aβ (beta) fibres (mechanical touch)
- Activates inhibitory neuron
- Pain signal blocked
Is it really true that "rubbing it" relieves the pain?
MECHANISMS TO MITIGATE PAIN
Assessment Tools
Validated Pain Measures
Pain Measures
Things to look for in Pain Assessment
- Nonverbal signs of pain (crying/grimacing)
- How long has the patient been taking the drug?
- Are they in pain – how could sleep be involved?
- Are they anxious?
- What is going on in the patient's life?
- What are their social circumstances?
Lorimer Moseley: Neuroscience researcher explains how the brain can be tricked into perceiving pain