L14 - Pain 3 Flashcards
What has higher threshold: nociceptive or inflammatory?
Nociceptive
Which is spontaneous pain: nociceptive or inflammatory?
Inflammatory
Where does pain perception occur?
The brain
The thalamus is the primary brain region linking sensory receptors to cerebral cortex EXCEPT for
Olfactory
The 3 submodalities of somatic sensation are:
Touch, proprioception and pain
Topographic organisation of spinothalamic tract
C-fibres tend to go to ?
Output neurons are located in lamina _ _ and _ and some of the deeper lamina
Only _% of neurons in spinal cord are projection neurons
Topographic organisation of spinothalamic tract
C-fibres tend to go to periphery of laminae of dorsal horn
Output neurons are located in lamina 1, 4, 5 and some of the deeper lamina
Only 5% of neurons in spinal cord are projection neurons
Brain areas activated by acute pain?
Anterior cingulate gyrus, posterior parietal cortex, Insula, S1, S2
Spinothalamict tract aka anterolateral system aka ventrolateral system - what info does ant and lat pathway convey? When does pathway decussate?
Anterior pathway - info about firm pressure and crude touch (sense that someone has touched you but you can’t localise where)
Lateral pathway - conveys pain and temperature
Decussates at the level of the spinal cord - hence is a contralateral pathway
Brown-Séquard syndrome
Damage to one half of the spinal cord, resulting in paralysis and loss of proprioception on the same (or ipsilateral) side as the injury or lesion, and loss of pain and temperature sensation on the opposite (or contralateral) side as the lesion
Segregation (labelled lines)
1) Topographic
2) Anatomical class of primary nociceptor
3) Response properties
1) Dermatome, organ, tissue structure
2) A delta or C fibre, chemical class
3) Low threshold, high threshold, wide dynamic range, thermosensitive
Intensity theory/Convergence
Strong activation of unspecialised neurons
Specificity theory/Labelled lines
Specialised low and high threshold neurons (LThN, HThN)
Combinatorial coding theory
Network response to activation of LThNs and HThNs
Is the “burning” sensation only attributed to noxious heat?
Burning quality assigned to both noxious heat and cold stimuli. Consequence of that is that we can have false assignments of sensory qualities to those inputs.
Referred visceral pain
Sensory primary afferents which project to the organs (except liver - which has almost no sensory innervation). Visceral pain will remap to somatic regions (e.g. upper GIT pain can extend to upper abdomen or limbs).
Referred visceral pain
Sensory primary afferents which project to the organs (except liver - which has almost no sensory innervation). Visceral pain will remap to somatic regions (e.g. upper GIT pain can extend to upper abdomen or limbs).
Lateral pain systems - what is it involved in?
Exteroception, Input directed to somatosensory motor cortices, defensive responses
Medial pain systems - what is it involved in?
Interoception, Input directed to emotional pain regions (Anterior cingulate cortex and Insula cortex). Input coming from lamina 1.
Can analgesia be conditioned in a rat?
When rat is experiencing fear - it shows an endogenous hyper analgesia (reduced pain sensitivity)
It is measured is by two ways-Time it takes to lick its paw
-Time it takes to flick its tail
Fear responses include
- Defensive behaviour
- Autonomic arousal
- Hypoalgesia (inhibiting ability to feel pain)
- Reflex potentiation
- Stress hormones
Fear responses include
- Defensive behaviour
- Autonomic arousal
- Hypoalgesia (inhibiting ability to feel pain)
- Reflex potentiation
- Stress hormones
Amygdala has 2 parts
1) Cortical part - receives input from thalamus and cortex
2) Central part - sends output that projects to regions of the brainstem responsible for producing fear responses
What receptor is responsible for causing analgesic effects when taking morphine?
U (miu)
What receptor for:
- POMC -> Beta-endorphin
- Proenkephalin
- Prodynorphin
- Pro-orphanin FQ
-u (miu)
This pathway contains two classes of neurons: OFF cells? ON cells?
OFF - activated by endorphins and morphine and inhibit pain transmission
ON - facilitate pain signals and are stimulated by noxious stimuli and certain psychological factors
NSAIDS - effective when injected into?
Cannabinoids - effective when injected into?
TCAs, SNRIs, opioids and a2 adrenoceptor agonists - effective when injected into?
PAG
RVMM
Spinal cord
