Physiology and Pathophysiology of Pain Flashcards
What is pain?
Pain is an unpleasant sensory and emotional experience which we primarily associate with tissue damage or describe in terms of such damage or both
What is noiciception?
The detection of tissue damage by specialized transducers connected to A - delta and C fibers
What part of the noiciceptor detects pain?
Free nerve endings
What type of stimuli do noiciceptors respond to?
Thermal
Chemical
Mechanical
Noxious stimuli
Which type of nerve fibre is responsible for fast pain? Slow pain?
Fast pain - A delta
Slow pain - C fibres
What are the three types of neurone found predominantly in the grey matter?
Low threshold mechanoreceptive neurons (layer 3 and 4) - receive input from A beta fibres
Noiciceptive specific neurons (layer 1 and 2) receiving input from C and A delta fibres
WDR (wide dynamic range) (layer 5) - main input is A beta responds to both noxious and non-noxious stimuli via interneurons.
Where do primary noiciceptive afferent impulses primarily end?
In the dorsal horn
What is the anterior spinothalamic tract responsible for?
Sensation of simple touch
What is the lateral spinothalamic tract responsible for?
Conveys fast and slow pain
(pain and temperature sensation)
Which rexed lamina does the spinothalamic tract arise in?
Arises in the rexed lamina 1,2 and 5
Where does the lateral spinothalamic tract end?
Terminates in the ventroposterior thalamic nuclei
Where does the ventroposterior thalamic nuclei feed into?
The somatosensory cortex to facillitate the spatial, temporal and intensity discrimination of painful stimuli
Where does the ventral spinothalamic tract project?
To the medial thalamic nuclei
Where does the medial thalamic nuclei project to?
Cortical regions such as anterior cingulate and insular cortex as well as other parts of the limbic system
Summary
Where does pain perception occur?
In the somatosensory cortex
Where do descending pathways arise from that usually descrease the pain signal?
Arise from the periaqeductal grey matter
travel from the brain to the dorsal horn