Pain Flashcards
What are the 4 processes of Nociception?
Transduction
Transmission
Modulation
Perception
What are pain receptors called?
Nociceptors
What occurs during Transduction?
Nociceptors only respond to damaging or potentially damaging stimuli
They transduce stimuli into receptor potentials
A𝛿 & C fibres - polymodal nociceptor
What occurs during transmission?
Nociceptive message is transmitted from periphery to CNS by axon of primary afferent nociceptor
Describe transmission from the PNS to the CNS
TRANSDUCTION
- Primary afferents release chemical transmitters (Substance P, Glutamate etc) from terminals
TRANSMISSION
- This activates second order neurons as the message travels via DRG to the dorsal horn via Na & Ca channels
- AP’s are then conducted to the CNS via C fibre & A delta primary afferents
- Primary afferents contact second order pain transmission neurons in spinal cord which relay the message to the higher brain centres
What occurs during Modulation?
Neural process that acts specifically to alter activity in the transmission system
Descending Noradrenergic projections arise almost entirely from Locus Coeruleus regions - INHBITORY
Descending Serotonergic projections arise entirely from ROSTAL Ventricular Medulla (RVM) regions - FACILITATORY & INHIBITORY
What are the 2 types of pain?
Acute pain
Chronic Pain
What are the processes that underlie the development of chronic pain?
Peripheral Sensitisation
Central Sensitisation
What is Peripheral sensitisation?
Produces an increased pain response due to nociceptors producing lots of neuropeptides
Leads to
- Primary hyperalgesia - normally painful stimulus - more painful
- Allodynia - normally non-painful stimulus - painful
- Upregulation of existing receptors
- Upregulation of new receptors
Reduction of threshold for nociceptor to fire
Pain restricted to site of injury
What is Central sensitisation?
Amplification of pain by CNS mechanisms
Mechanisms can be driven by different molecular effectors including kinases
Produces pain sensitivity long after initiating cause - abnormal
What are the different types of pain
Inflammatory - Pain symptoms associated with an inflammatory response
Neuropathic - Pain caused by a lesion or dysfunction of the nervous system
Central - Pain caused by a lesion or dysfunction of the central NS
What are some examples of Eicosanoids?
Leukotrienes,
Lipoxins,
Thromboxane’s,
Prostanoids,
All have important roles in inflammatory responses
What are 2 types of Prostaglandins?
PGE2 & PGI2
Most important eicosanoids with respect to pain producing and enhancing aspects
Generally thought of as enhancers of pain
Why is neuropathic pain often chronic?
Nerves have a limited capacity to fix themselves
Method of treating Nociceptive pain?
Treat pain at peripheral source
