Pain & Thermosensation Flashcards
What are the 3 classifications of pain?
Nociceptive, Inflammatory & Pathological
How is pain from the skin perceived?
Well-localised - pricking, stabbing, burning
How is pain from the muscles perceived?
Poorly-localised - aching, tenderness, cramping
How is visceral pain perceived?
Poorly-localised - often referred to a somatic structure.
What are the classes of nociceptor?
Aδ-fibres and C-fibres (NB - not all Aδ- and C-fibres are nociceptors)
What do Aδ-fibres do?
They are fast-acting mechano- and thermo-receptors
What do C-fibres do?
They are slow-acting (unmyelinated) polymodal receptors.
What is ‘frequency coding’?
The phenomenon whereby the rate of action potential discharge correlates with the intensity of the applied stimulus.
What are the sub-classifications of Aδ-fibres?
Type I - high threshold mechanoreceptors
Type II - mechano- & thermo-receptors
What are the sub-classifications of C-fibres?
C-MH (mechanical and heat)
C-M (Mechanical only)
C-H (Heat)
C-MiHi (normally insensitive but can be activated by inflammatory mediators)
At which laminae of Rexed int he dorsal horn of the spinal cord do nociceptive C- and Aδ-fibres mostly terminate?
Laminae I and II. Also V for Aδ-fibres.
How do visceral afferents from visceral nociceptors reach the CNS?
Following sympathetic pathways into the dorsal horn.
What is referred pain?
Pain felt in a part of the body other than its actual source.
What causes referred pain?
Some visceral and skin afferents converge on the same spinothalamic neurones and so the brain can mix-up the signals.
What is viscerosomatic pain?
A pain resulting due to inflammatory exudate from a diseased organ contacting the soma (body wall) e.g. peritonitis.
