week 10 Flashcards
Definition of pain:
“An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage”
How do we feel pain?
- The nervous system’s transmission
- The body’s modulation of pain
- The mind’s interpretation of stimuli and their meaning.
Definition of Nociception:
The neural process of encoding noxious stimuli
Noxious stimuli
= a stimulus (i.e. mechanical, thermal or chemical) that is damaging or threatens damage to normal tissue.
Distinguish between pain and nociception.
Nociception = noxious stimuli activates nociceptors and sends a message to the CNS (spinal cord and brain).
Pain is the perception of an aversive or unpleasant sensation arising from a specific region of the body.
Nociception is Neural (the Input)
Pain is Perception (the Output)
In order for nociception to occur, FOUR physiological processes must occur:
- Transduction
- Conduction
- Transmission
- Perception
Pathophysiology of Pain
Transduction – conversion of a noxious stimulus into an action potential in the peripheral terminals of sensory fibers.
Conduction – the passage of action potentials from the periphery along axons towards the central nervous system
Transmission – the synaptic transfer of input from one neuron to another.
Perception – when the sensation is perceived by the brain
- Aδ fibres ( a delta) = fast pain
- Myelinated fibers = conduct signals quickly (5–40 m/s).
- Fast, sharp, and localized pain.
- Lateral spinothalamic tract, for processing in the primary somatosensory cortex.
- This allows for the precise localization of pain.
C fibres = slow pain
- Unmyelinated fibers = conduct signals more slowly (0.5–2 m/s)
- Slow, dull, aching, or burning pain, which is diffuse and poorly localized.
- Spinothalamic and Spinoreticular tracts.
- Connect to the thalamus, Reticular formation, and Limbic structures,
- = emotional and motivational aspects of pain.
Why we experience pain
- Protective
- Alert system
- Helpful – avoid injury or life-threatening situations
- Pain is subjective - everyone experiences pain differently.
pain is influenced by
- Influenced by:
- Sleep
- Exercise
- General health
- Attitudes
- Beliefs
- Mood
- Environment
- Age
- Experiences
- People around you
There are two ways to classify the type of pain someone is in:
- Duration of pain
- Acute
- Sub-acute
- Chronic/Persistent - And, by the pathophysiology of pain:
- Nociceptive pain
- Neuropathic pain
- Nociplastic pain
Acute Pain
- Up to 6 weeks.
- Associated with actual or potential tissue damage
- Reflective of tissue healing times
- Resolves once tissue has been offloaded or healed
Sub-Acute Pain –
- From 4 – 12 weeks.
- Associated with actual or potential tissue damage
- Typically indicates delayed healing or complications such as infections or prolonged inflammation.
- Resolves once tissues have healed
Chronic or Persistent Pain –
- Pain continues beyond typical tissue healing timeframes.
- Very dependent on the tissues that have been damaged and the extent of that damage,
- Generally agreed to be pain that is persistent beyond 3-6 months.
Nociceptive Pain
- Pain is typically related to actual or threatened tissue damage (to non-neural tissue)
- Designed to protect us from injury or harm
- Caused by the activation of nociceptors and subsequent interpretation by the brain as pain.
- Pain resolves as tissue healing takes place
eg - Pain following injury
Neuropathic Pain
- Neuropathic pain arises from abnormal neural activity secondary to disease, injury, or
dysfunction of the nervous system. - Pain is related to a lesion of the neural tissue
- May be felt at the site of injury or far away from the injury
eg - Phantom limb pain
Nociplastic Pain
- Pain the arises from altered nociception despite no clear evidence of a stimulus that is
activating nociceptors - Absence of actual or threatened tissue damage
- Absence of disease or lesion to neural tissues
- Can be recurring or persistent in nature
- Often associated with comorbidities (stress, mood disorders, grief, chronic illness)
eg - Chronic non-specific low back pain
How do we feel pain?
- The nervous system’s transmission
- The body’s modulation of pain
- The mind’s interpretation of stimuli and their meaning.
Modulation of Pain
Where can this happen?
- Receptor (PNS)
- Dorsal horn / spinal cord (CNS)
- Supraspinal structures (CNS)
Modulation of Pain Plasticity
changes in the properties or behaviour of neurons.
* This us an unhelpful and maladaptive application of neuroplasticity
Sensitisation
“An increase in responsiveness of nociceptive neurons to their normal input, and/or recruitment of
a response to normally subthreshold stimuli.
Sensitisation can be in
- Peripheral sensitisation
- Central sensitisation
Sensitisation may lead to changes in
- Thresholds
- Mechanisms
- Neurotransmitters
- Degree of activation
- Duration of activation
