Physiology of Pain Flashcards
Define pain
An unpleasant sensory and emotional experience which is associated with actual tissue damage or described in terms of such damage
What are the three forms of pain?
- Nociceptive - specific primary sensory afferent neurones normally activated by intense noxious stimuli
- Inflammatory - activation of immune system by tissue injury or infection
- Pathological
Which type of pain is not adaptive?
Pathological pain
What is pathological pain?
Pain that outlives its biological or adaptive purpose - neuropathic = damage to neural tissue
dysfucntional - no identifiable damage or inflammation eg fibromyalgia
What is adaptive pain?
Pain which serves as an early warning system to detect and minimise contact with damaging stimuli
(nociceptive and inflammatory pain)
What threshold level does nociceptive pain have?
High
It is activated by intense stimuli
Which type of pain is associated with pain hypersensitivity?
Inflammatory pain
What is pain hypersensitivity?
An increased behavioural response to a constant painful stimulus in order to allow for healing
This is adaptive
What is allodynia?
Increased sensitivity to painful region and when non-painful stimuli cause pain.
This is to ensure constact with the painful area is minimised to allow for healing
Which two types of pathological pain exist?
- Neuropathic pain
- Dysfunctional pain
What is neuropathic pain?
Pain caused due to nerve cell damage
What is dysfunctional pain?
A potentially irregular processing of inoculous information in the CNS
What is the name of the condition that results in complete absense of pain?
Congenital insensitivity to pain (CIP)
Caused by a loss of function mutation affecting voltage activated sodium channels which are highly expressed in nociceptive receptors
What are the two types of nociceptor?
- Aδ fibres
- C fibres
What are the 3 main differences regarding Aδ and C nociceptive fibres?
- Aδ fibres are thinly myelinated, C fibres are not
- Aδ fibres only respond to thermal or mechanical stimuli whilst C fibres respond to all noxious stimuli (polymodal)
- Aδ fibres confer “fast” pain, whilst C fibres confer “slow” pain
What is the pathway from the sensory receptor to the CNS for pain?
- Nociceptor
- Second order neurone
- Spinothalmic or spinoreticulothalmic tracts
Which type of nociceptive fibre has:
a) A really high heat threshold (53 degrees)
b) A more moderate heat threshold (43 degrees)
a) Aδ type I
b) Aδ type II
What is the neurotransmitter associated with nociceptive receptors?
Glutamate
How is nociceptive information sent to the CNS within the dorsal horn?
- Glutamate
- Peptides (substance P and neurokinin A)
What is the efferent function of C fibres?
Pro-inflammatory mediator release from peripheral terminals (calcitonin and substance P)
Which nerve fibre transmits proprioceptive stimuli?
Aβ fibres
How many major nociceptie tracts are there?
2
what are the 4 distinct processes int eh physiology of pain
transduction - noxious stimulus into electrical activity
transmission - pain signal as nerve impulse
modulation - modification of pain transmission in nervous sytem - opioids
perception - conscious expereince of pain
What is nociceptive pain?
nromal response to injury by noxious stimuli
referred pain - what is it?
Pain developed in one part of the body but can be felt elsewhere; usually deep pain or visceral pain is referred
