Lecture 4 Flashcards
(27 cards)
What is pain?
Pain is an unpleasant sensory or emotional experience associated with actual or potential tissue damage, or described in terms of such damage
What is phantom pain?
Pain felt by amputees in parts of the body that are no longer there
What is pain known as in animal models?
Nociceptive responses
Because these models may not experience ‘pain’ as we know it, instead just negative stimuli
What neurons detect pain?
Nociceptor
Different neurons for pain rather than just normal neurons firing more. E.g. thermoreceptor when the temperature is not dangerous; but then nociceptor takes over if stimuli becomes dangerous
Describe two specialised receptors introduced by Heinbecker
A-delta
faster than 2.5m/s, high threshold mechanoreceptors, sharp pain
C
Slower than 1m/s, polymodal (Heat, pressure and noxious chemicals)
How is pain conducted from receptor to the spinal cord?
Up the axons to their cells bodies in the Dorsal Root Ganglion, and then the spinal cord
Which voltage gated sodium channels are important for nociception?
NaV1.7 and NaV1.8
What is a special characteristic of NaV1.7?
Sensitive to TTX
What disease is caused by Nav1.7 mutations?
Erythromelalgia
Burning pain triggered by warmth/exercise
e.g. F1449V, half the current required to generate an action potential
Give some example Nav1.7 mutations that lead to pain insensitivity
W897C mutation
I767C frame shift
What stimuli are C fibres sensitive to?
Histamine, ACh and prostaglandins (the inflammatory soup). Factors released due to tissue damage
How does aspirin work?
Blocks Cycloxoygenase, or prostaglandin synthase, by modifying Ser530
What other drugs inhibit COX?
Ibuprofen and paracetamol
non-steroidal anti-inflammatory drugs
What two types of molecule have been used to target the TRPV1 channel for pain relief?
Agonists
Desensitisation for migraine, surgery, and neuropathic pain
Anatagonists
Compete and block channel, but has effects on body temperature
What is the substantia gelatinosa?
The jelly like substance
Pain neurons project onto this column of the spine. The SG acts as map for the body; where the neurons project too either side of mid line tell you where the receptor is. SG made up of layers, and inter neurons project onto dorsal horn cells which combines signals and projects onto thymus.
What do the inter neurons use as neurotransmitters?
Enkaphalin and substance P
What are the three Enkaphalin receptors?
Mu, Delta and Kappa
What types of Enkaphalin exist?
Leu and Met enkaphalin
What opioid’s are used for pain relief?
Morphine, codeine and pethidine
What effect does capsaicin have on substance P?
Blocks substance P action
What is the scientific basis for ‘mummy rub it better’?
Neurons firing onto the spinal cord from adjacent areas will inhibit the feeling of pain from nearby damage
What is used to transport toe action action potential up to the thalamus?
The spino-thalamic tract
What inputs can the cortex have to control the gate?
Cause release of noradrenaline and serotonin
What drugs can be used to make us of the cortex’s role in the gate control theory?
Analgesics
Serotonin and noradrenaline re-uptake inhibitors
Monoamine oxidase inhibitors
