Pain + Analgesia Flashcards
MLA Content Y3
What is Nociceptive pain?
Acute pain.
- e.g. Pin prick, Visceral distension.
What is Inflammatory pain?
Prolonged pain
- e.g. sunburn, inflamed wound.
What is Pathological pain?
Pain with no protective function that results from abnormal nervous system function.
- e.g. neuropathic or dysfunctional.
What type of pain is adaptive and has a high threshold?
Nociceptive pain
Adaptive: serves as warning system to minimise contact with damaging stimuli.
High Threshold: Only provoked by intense stimuli activating nociceptors.
What type of pain causes hypersensitivity to noxious stimuli and allodynia (innocuous stimuli now elicit pain)
Inflammatory pain.
- Caused by activation of the immune system in injury, or infection.
What type of receptors respond to low threshold stimuli?
Low Threshold Mechanoreceptors (LTMs)
- mediate touch, vibration and pressure.
What type of receptors respond to High threshold stimuli?
Nociceptors.
- Information from High threshold nociceptor units can be perceived as painful but is subject to modulation.
What are the two subtypes of Nociceptor neurons?
A Delta-fibres (“first” or “fast” pain intensity - pin pricks, stabbing)
C-fibres (Burning, throbbing, Cramping.)
Where in the spinal cord do Primary afferent axons terminate?
Centrally in the dorsal horn of the spinal cord.
Where do the Nociceptor C and A-Delta fibres terminate?
Superficially in laminae 1 and 2 (also 5 for A-Delta fibres)
What kinds of fibres are involved in the Dorsal column medical lemniscal pathway?
A-Alpha and A-Beta Fibres
Decussation at the pyramid of the medulla.
What kinds of fibres are involved in the Anterolateral system (Spinothalamic tract) ?
A-Delta and C Fibres.
Decussation at level of the cord at point of entry via Lissauer’s tract.
Which analgesic acts at the site of injury by decreasing Nociceptor sensitisation in inflammation?
NSAIDs
- They do this primarily by blocking synthesis of prostaglandins
Which Analgesic suppresses synaptic transmission of nociceptive signals in the dorsal horn of the signal cord?
Opioids
Which analgesic reduces pain by activating (or potentiating) descending inhibitory controls?
Opioids
Which Analgesic reduces nociception and pain by suppressing nerve conduction through blocking / inactivating voltage-gated sodium channels?
Local Anaesthetics, such as lidocaine
Which Analgesic reduce nociception and pain by targeting ion channels upregulated in nerve damage?
Gabapentinoids.
Which enzymes do NSAIDs inhibit to prevent accumulation of prostaglandins?
COX-1 and COX-2
Where do Brain regions involved in pain perception (cortex, amygdala) and the spinomesencephalic pathway project to?
The Periaqueductal grey (PAG)
What does the PAG do?
Involved in pain modulation
- The PAG contains neural circuits that can inhibit or facilitate the transmission of pain signals in the spinal cord and brainstem. Activation of certain areas within the PAG can lead to analgesia (pain relief), while inhibition can increase sensitivity to pain.
Which areas in the spinal cord does the PAG influence to to reduce pain sensation?
The locus coeruleus - noradrenergic effects
The nucleus raphe magnus - Serotonergic effects
Overall the PAG is important in coordinating adaptive responses to various internal and external stimuli, including pain, threat, and emotional arousal, thereby contributing to the overall regulation of physiological and behavioural functions.
Which receptors do opioids work on?
mainly bind to Mu-receptors.
Also:
- Delta-receptors
- Kappa-receptors
(The PAG also has opioid receptors - their activation disinhibits descending projection neurons)
What type of receptors mediate Opioid action?
G protein-coupled opioid receptors.
