Pain and Nociception Flashcards
How can pain be classified
Nociceptive pain and clinical pain
How can clinical pain be classified
Acute and chronic
What is nociceptive pain
Normal pain - mediated through As and C fibres
Only elicited when intense/noxious stimuli threaten to damage normal tissue
Protective function
Describe acute clinical pain
Results from soft tissue injury or inflammation
Serves as a protective function
Describe chronic clinical pain
A sustained sensory abnormality
Result of an ongoing peripheral pathology
Pain is maladaptive, offering no survival advantage
What are different attributes of pain as a symptom
Location Quality - sharp stabbing, dull aching Intensity Frequency/duration Provoking/relieving events
What is referred pain
Pain felt in one part of the body but the pathology is elsewhere
Pains tend to be referred to sites of common embryological origin
Due to a convergence of inputs in the CNS
What are nociceptor endings
Free nerve endings with a high threshold of activation that respond to intense noxious stimuli associated with pain
What nerve fibres are nociceptors
As fibres - noxious mechanical/heat
C fibres - polymodal - respond to quite a few stimuli which eventually lead to a dull, aching sensation
Give examples of different neural pathways in the CNS
Mechanoreception (touch)
Nociception (pain)
Which CNS relay nerves are involved in nociception
Spinal dorsal horn
Spinal trigeminal nucleus
Which CNS pathways are involved in nocicpetion
Spinothalamic tract
Anterior trigeminothalamic tract
Which areas of the forebrain are involved in nociception
Primary sensory cortex
Subcortical areas
What are factors that affect perception of pain
Genetic Molecular Cellular Anatomical Physiological Psychological Social
Describe the molecular basis of pain
SCN9A gene encodes a-subunit of voltage gated Na+ channel Nav1.7
Nav1.7 is strongly expressed in nociceptive afferents (receptor endings)
SCN9A mutation - loss of Nav1.7 function - inability to experience pain
Give examples of psychological factors in pain
Sex Age Cognitive levels Previous pairs Family Culture
Give examples of situational factors in pain
Expectation
Control
Relevance
Give examples of emotional factors in pain
Fear
Anger
Frustration
Describe the gate control theory of pain
Rubbing sore areas lessens the perception of pain
Noxious stimuli activate C or As fibres which project into dorsal horn activating second order neurons which activate tertiary, eventually lessening the pain
Rubbing recruits Ab fibres, branch comes off called inhibitory interneurone which block activity of pain fibres so the pain disappears
What is the triple response
Mild trauma to the skin region, red line appears - the red line is the point of trauma - this is called the red reaction
The area around the skin appears very pale and swells up - this is wheal
After this, further away the skin appears red and discoloured - this is called flare
What occurs after mild trauma to the skin
Release of potassium, prostaglandins and bradykinin which are released from plasma if there is any damage to capillaries
There is also release of 5-HT from platelets
The nerve endings of skin can express substance P and CGRP
What does substance P and CPRG do to mast cells
Cause their degranulation
What does CPRG do
Causes dilation of blood vessels which is what gives rise to the flare region as there is more blood flowing through them making the skin appear red
What does substance P do
In the wheal region, the release of substance P causes plasma extravasation meaning they are leaky and it causes oedema
