Week 5 Part 2 Flashcards
What can lead to central sensitisation at an activation of CNS?
Low level c-fibre activity
What are acting in the DRG?
Sympathetic neurons
What is recorded in Lamina 5?
Multimodal cells
What are changes in the nervous system?
Receptive field expansion due to central sensitisation
What are responses of uninjured fibres?
Mediate Allodynia and hyperalgesia
What becomes spontaneously active?
C fibres
What sprouts peripherally?
C fibres
What are phenotypic switching due to?
Trophic factors
What are the roles of C-fibres?
Neurotransmitter down-regulation
Loss of glomerular complexes in Lamina II
Reduced ability to activate spinal cord neurons
What are the roles of A-fibres?
Phenotypic switching of neurotransmitters
Substance P and CGRP are produced
Increased ability to activate spinal cord neurons
What does A-fibre marker studies suggest?
AB fibres sprout into Lamina II
How many afferents are found in the injured state?
23 hair follicles
How many afferents in the control state?
13 hair follicles
What is A-fibre markers inadequate?
Phenotypic switching in the cells transporting CTB-HRP
What happens after injury?
CTB labels the unmyelinated fibres too
What is AB fibre genetically labelled with?
PV promoter-driven tomato red fluorescence protein
What is not labelled in Lamina II despite allodynia?
No sprouting
What does A fibre bulk labelling method show?
Phenotypic switch
What does single fibre fills show?
Wide morphological variation
What does C fibre binding studies show?
Extracellular spread
What is central sensitisation?
Long-term potentiation in the spinal cord
What does C fibres acting on second order neurons in spinal cord release?
Glutamate/ substance P/ neurotrophic factors
What is monosynaptic strengthening?
Opening up Ca2+ channels in the second order neurons and allowing this cell to respond more effectively to C-fibre input
Strengthening of that cell to consequence stimuli
What is found in second-order cell?
Heterosynaptic strengthening
How can Ab-fibres maintain the increased activity in second order nerve?
Releasing substance p
acting on NK1 receptors
