Pain and analgesics second half of 1 2.0 Flashcards
Where does the AP go after it has gone through the first synapse in the spinal cord?
Crosses over to the other side of the body and goes up into the brain, into the thalamus
What type of input can the somatosensory part of the cortex receive?
Touch and nociception
What does the somatosensory cortex do with the touch and nociception?
Tells the brain where it has come from
Role of insular and anterior cingulate cortex in nociception?
Tells the brain that it is pain that is being experienced, affect your mood
How is the body mapped regarding pain perception and location?
As you go round the outside of the somatosensory cortex, different parts of it receive input form different body areas
What is the pain pathway to the brain?
Spinothalamic pathway/tract
Why is pain referred?
Not enough space in somatosensory cortex to have an acute sensation to map every part of the bodys pain
Which body parts have a good pain mapping (know where the pain is coming from)?
Skin
Which body parts have a poor pain mapping (don’t know where the pain is coming from)?
Internal organs
Where does pain sourced in the oesophagus feel like its coming from?
Heart
What can hurt when having a heart attack?
Left arm
Which neurons are shared in referred pain?
Second order
What is the second order neuron?
The one after the first synapse in the spinal cord
What is hyperalgesia?
Increased response to a noxious stimulus
What is allodynia?
Painful responses to a non-noxious stimulus
Why is hyperalgesia a thing?
To protect already injured/damaged areas of the body
How does nociceptor sensitisation work?
Cut skin–> skin cells break–> intracellular components of skin cells is released into extracellular space–> some of these components are H+, ATP, K+ which are nociceptor agonists
Why does an elevated conc of extracellular K+ increase the amount of APs fired from a neuron?
Conc grad is disrupted meaning it is harder for the neurons to repolarise, makes them more excitable
What is unusual about nociceptive neurons?
They can release NTs from their dendritic end
Which NT is released from the dendritic end of nociceptive neurons?
Substance P
What does substance P do to blood vessels?
Activate receptors on blood vessels that makes them leaky
Outcome of substance P’s action on blood vessels?
More nociceptor agonists are released, generating more nociceptive APs
Which cells does substance P recruit?
Mast cells
Action of mast cells?
Release histamine which makes blood vessels leaky
Which three molecules are used for healing the part of the body that has been damaged?
Bradykinin, prostagladin, neural growth factor
What does nerve growth factor do?
Activates TrkA receptor–> this sensitises nociceptors by lowering their opening threshold
What is peripheral sensitization?
Increased sensitivity of peripheral nociceptors
What is central sensitization?
Increased transmission in spinal cord
Which fibres do itch sensations travel down?
Adelta and C
Difference between pain and itch?
Analgesics don’t inhibit itch, can imagine an itchy sensation but not a painful one
What kind of input cures an itch?
Nociceptive (scratching it hard)
