N11- Pain and nociception Flashcards
Name some causes of pain in dentistry.
- dentine sensitivity
- caries
- trauma
- cracked cusp
- dry socket
- salivary gland pain
- sinusitis
what is the sensation of nociception and what are its non-sensory effects?
sensation: Pain
non-sensory effects: protective reflexes,cardiovascular reflexes and alertness
what is the sensation of thermoreception and what are its non-sensory effects?
sensation- hot/cold
non-sensory- thermoregulatory reflexes,, sweating, shivering
what is the sensation of mechanoreception and what are its non-sensory effects?
sensation- touch
non-sensory effects- stretch/protective/salivary reflexes
what is the sensation of proprioception and what are its non-sensory effects?
sensation- position sense
non-sensory effects- stretch reflexes
what is the sensation of gustation and what are its non-sensory effects?
sensation- taste
non-sensory effects- salivary reflexes
what is the sensation of olfaction?
sensation- smell
what is the definition of pain?
an unpleasant sensory and emotional experience associated with actual or potential tissue damage
what is the definition of nociception?
the activation of neural pathways by stimuli that damage or threaten to damage tissues
what is a noxious stimulus?
potentially damaging stimulus
what is a nociceptive stimulus?
a stimulus that activates nociceptive pathways (in research)
what does pain normally signify?
- caries
- abscess
- TMJ
- fracture
what is the name for pain in healthy areas?
referred pain
Name a significant pathology that is not painful.
tumours
why is pain useful?
- avoid further damage
- future avoidance
what is the name when you don’t feel pain?
congenital insensitivity to pain
what are the 2 types of pain?
acute- fast, sharp pain
chronic- slow, burning pain
what are the 2 dimensions of pain?
Sensory-discrimitve - quality, intensity and location
Affective- emotional aspects
How do you study pain on animal models?
-Nociception - electrophysiological recordings
– behavioural responses – e.g. vocalisation
– reflex studies
how do you study pain on humans?
– microneurography
– psychophysical studies – blister studies
– reflex studies
what are nociceptors?
receptors that respond to noxious/nociceptive stimuli
what are nociceptors classified by?
- parent axon
- stimulus
Describe the structure of the axons in nociceptors.
- C-fibre- fine and unmyelianted, diameter 0.2 to 1.5microm, conduction velocity 0.2-2ms
- Ad fibre- fine myelinated, diameter 1-5micrometeres, conduction velocity 5-30ms
what axon is for fast and sharp pain?
Ad fibres
what axon is for slow and burning pain?
C fibres
what do Ad mechanical nociceptors respond to?
strong mechanical stimuli
what do Ad polymodal nociceptors respond to?
all types of noxious stimuli
what type of nociceptors is C-fibre?
polymodal
Describe direct nociceptor transduction.
Stimulus acts directly
– Mechanical, Chemical and thermal
-Membrane permeability changes - Graded potential
Describe indirect nociceptor transduction.
- Tissue injury / inflammation
- Chemicals released -> nerve ending
Describe mechanical nociceptor transduction.
- Stimuli: pinch, pressure
- Mechanically sensitive ion channels
Describe thermal nociceptor transduction.
Vanilloid Receptors:
– >45°C: TRPV1
– >50°C: TRPV2 receptor
what gives the sensation of warmth?
capsaicin
what does capsaicin activate?
TRPV1 at <45°C – Spicy foods (chilli peppers)
what activates nocicptive nerve ending?
- ATP
- H+
- K+
what activates or sensitize nociceptive nerve endings?
- bradykinin
- histamine
- serotonin (5-HT)
what sensitizes nociceptive nerve endings?
prostaglandins
what chemicals are released from nerve endings?
substance P
where is substance P present?
fine peripheral fibres
substance p has a role in what?
central transmission
what is caused by substance P being released from free nerve endings?
- vasodilation
- mast cell degranulation
- axon reflex
Describe the sensitisation of nociceptors.
-Inflammatory “soup” +/- Axon reflex effects produce peripheral sensitisation
– Lowers the threshold
Allodynia = pain produced by a stimulus that
would NOT normally produce pain – e.g. Sunburn, tender tooth
what blocks prostaglandin formation?
Cox inhibitors
Describe non-steroidal anti-inflammatory drugs.
-Aspirin, Ibuprofen, Indomethacin
– non-selective COX inhibitor
what does experience of pain depend on?
- usually, but not always, strength of stimulus or degree of tissue damage
- emotions
- past experience of pain
- ability to comprehend causes and consequences
what does the sensory nervous system do?
-informs the CNS of the internal and external environment
what is the role of the nociceptive system in the sensory nervous system?
signal the threat or occurrence of injury
where are nociceptors especially found?
cornea and tooth pulp
where are nociceptors lacking?
brain, liver,lung
