Pain experience 1 Flashcards
What are the 2 different dimensions of pain?
Sensory – discriminative – Quality, intensity and location
Affective – Emotional aspects
informs the CNS of the internal and external environment
What is the role of the nociceptive system?
role of the nociceptive system is to signal the threat or occurrence of injury
What are the 2 types of nerve fibres?
Aδ-fibre - fast pain, sharp
- Fine
- Myelinated axon
C-fibre - slow pain, burning
- Fine
- Unmyelinated axon
What are the 2 types of nociceptors?
Aδ mechanical nociceptors
• respond to strong mechanical stimuli
Aδ polymodal nociceptors
• respond to all types of noxious stimuli
What is the only type of C-fibre nociceptors?
polymodal C-fibre nociceptors
– Respond to all types of noxious/nociceptive stimuli
What are the 2 Tooth pulp afferent nerves?
- Aδ myelinated afferents (touch)
- C-fibre unmyelinated afferents
If you stimulate a nerve trunk what can you get?
Double pain because it wil contain A delta fibres AND C fibres
What is Nociceptor transduction?
Where mechanical, chemical or thermal stimulus is converted into a electrical change and if that is sufficient to reach threshold then we fire off action potentials up the nerve to the CNS
What are the 2 factors involved in Nociceptor transduction?
Direct:
Stimulus acts directly on the nerves
– Mechanical, Chemical and thermal
Indirect:
Tissue injury / inflammation
Effect of substances released from a nerve ending
In Nociceptor transductions what is the Direct: Mechanical Transduction?
Stimuli: pinch, pressure
Mechanically sensitive ion channels
What chemicals does Local tissue damage produce?
Algogenic substances - can activate or sensitise nerve endings
What chemicals can acitvate a Nociceptor nerve ending?
- ATP
- H+
- K+
What chemicals can acitvate or Sensitise a Nociceptor nerve ending?
- Histamine
- Serotonin
- Bradykinin
What chemicals can only Sensitise a Nociceptor nerve ending?
Prostaglandins
Example of a chemical released from nerve ending?
Substance P
Present in fine peripheral fibres
Substance P release causes:
– Vasodilation
– Increase in vascular permeability
– Mast cell degranulation
What can Sensitisation of nociceptors cause? (2)
Hyperalgesia = exaggerated response to a nociceptive stimulus
Allodynia = pain produced by a stimulus that would NOT normally produce pain – e.g. Sunburn, tender tooth
One of the ways to manage pain is for drugs like asprin to act on chemistry at a nerve ending. What are these drugs called?
Cox inhibitors
- Non-steroidal anti-inflammatory drugs
- e.g. Aspirin, Ibuprofen
Where is the Site of receptors of the following sensations?
- Touch
- Pain
- Cold
Touch = Periodontal ligament
Pain = Dentine/pulp, periodontal ligament
Cold = Gingiva, dentine/pulp
be familiar with this chart
What is the plexus of nerves called when they enter the pulp of a tooth?
Plexus of Raschkow
Why in relation to nerves is it sometimes difficult to localise dentinal/pulpal pain?
Nerves branch to supply more than 1 tooth pulp
What are the 3 Theories of dentinal sensitivity?
- Dentine is innervated
- Odontoblast receptor theory
- Hydrodynamic Theory
What is Dentine innervation Therory?
Dentine is innervated but nerves to not extend beyoned the innner third
What is Odontoblast receptor theory?
- Stimulus transduction via the odontoblast process
- Communication between odontoblast and primary afferents
- Problem:*
- No evidence of electrical, communication chemical synapses between odontoblast and nerve*
- Odontoblast process likely only extends 1/3 into dentine
What is the Hydrodynamic theory?
Apply Stimuli that causes pain to dentine:
– Increase fluid flow in dentine in vitro
– Generate action potentials in intradental nerves in vivo
– Action potential rate linked to fluid flow
Cold sensitivity may not be mediated by a hydrodynamic mechanism
