Nociception Flashcards
What are the fibres that transmit pain?
III (A delta), IV (C)
Which type of pain fibres are myelinated?
A delta
Do C fibres transmit
a) dull throbbing ache
b) fast sharp pain?
a
Do C fibres respond to
a) mechanical stimuli
b) mechanical stimuli and substances released by damaged tissues?
b
Different fibres from which ascending pathway synapse in the Rexed’s laminae?
Anterolateral system
Where on the Rexed’s laminae do A delta fibres synspase?
The top and the bottom
Where on the Rexed’s laminae do C fibres synapse?
Top layer
Where do the 1st order neurones from the anterolateral pathway decussate?
In the spinal cord at the tip of the dorsal horn
Where do the 2nd order neurones from the anterolateral system synapse?
Ventral posterior lateral nucleus in the thalamus
What is peripheral sensitisation?
Making nociceptors more sensitised
How do nociceptors become more sensitised?
Lower the threshold
Increase response to noxious stimuli
What is the purpose of peripheral sensitisation?
Reduces the likelihood of further damage
What causes sensitisation?
Release of chemicals after damage or inflammation
What is central sensitisation?
Sensitisation within the CNS.
Alters synaptic strength
Where does central sensitisation occur specifically?
AT synapses in the: Spinal cord Thalamus Amygdala Anterior cingulate nucleus
How does central sensitisation occur?
Nerve cells increase Ca2+ levels which activate pathways that form TF which up regulate formation of receptors
What is the Gate theory of pain?
Different sensory modalities (touch) interacts with other pathways in the spinal cord (pain).
Branches from touch pathways (interneurones) feed into pain pathways and block pain pathways
What fibres transmit information about touch?
1a, 1b, II
Where do 1st order neurones of the dorsal column pathway synapse and decussate?
In cuneate or gracile nucleus in medulla
In terms of pain what is the function fo the primary somatosensory cortex?
Localisation of pain
What would damage to the post central gyrus cause in terms of pain?
Inability to locate pain
How does the limbic system relate to pain sensation?
The hippocampus and amygdala are an affective component of pain they induce suffering
What is deafferentation?
Damage to afferent nerves causing changes to pathways and causes central sensitisation
What is referred pain and what causes it?
Feeling pain away from site of damage.
Caused by convergence of sensory neurones in second order neurones
How is pain controlled centrally?
Descending pathways from sensory cortex release endorphins which inhibit pain pathways
