Pharmacology Flashcards
What is the definition of pain?
An unpleasant and emotional experience, associated with actual tissue damage
What are the 3 forms of pain?
Nociceptive pain
Inflammatory pain
Pathological pain
What is nociceptive pain?
Adaptive - an immediate protective response, short lived
What is inflammatory pain?
Adaptive - assists in healing, persists over days, possibly weeks
What is pathological pain?
Maladaptive - no physiological purpose, persists over months, years or even a lifetime (has outlived it’s biological purpose)
What are nociceptors?
Specific peripheral primary sensory afferent neurones, activated by intense stimuli (thermal, mechanical, chemical) that are noxious
What are the subtypes of nociceptors?
A(delta) fibres
C fibres
Where does the transduction of a noxious stimulus into electrical activity occur at the nociceptor?
At the terminal
What are a delta fibres?
Responsive to mechanical/thermal stimuli. Have a thin myelin sheath and conduct AP’s at a moderate velocity. Mediate ‘first’ pain.
What are C fibres?
Respond to all stumuli.
Small diameter axon, no myelin sheath.
Slowly conduct.
Mediate ‘second’ pain.
Name some examples of first pain?
Lancinating, stabbing, pricking sensations
Name some examples of second pain?
Burning, throbbing, cramping, aching
What is first pain?
Occur immediately upon receiving the noxious stimulus and is mediated by A delta fibres. Short duration
What is second pain?
Kicks in slowly after noxious stimulus and develops slow then subsides slowly
What does long term noxious stimulation in the long term do?
Increase spinal excitability contributing to hyperalgesia and allodynia
What is behind hyperalgesia and allodynia?
Sensitisation of the peripheral and central terminal increasing efficiency of synaptic transmission meaning nociceptive signals are more likely to make their way from the primary afferent to the second order neurone
What is hyperalgesia?
Heightened pain sensitivity - to an already painful stimulus
What is allodynia?
Innocuous stimuli becomes a painful condition
Where does visceral pain originate from?
Nociceptors covering tissues or walls of hollow organs. Stretching, twisting, inflammation and ischaemia
What type of pain is poorly localised and dull, aching, throbbing?
Visceral pain
What type of pain is sharp and well localised?
Viscerosomatic
When does viscerosomatic pain occur?
When inflammatory exudate from a diseased organ contacts a somatic structure
What is the difference between pain and nociception?
Pain is the awareness of suffering. Nociception may occur in the absence of pain .
What determines whether pain is received or not?
Balance of input between Ab fibres and C/Adelta fibre population
When is the spinal gate open?
more activity in the C/Adelta fibre
When is the spinal gate closed?
More activity in the Abeta fibres
What are the brain areas involved in the pain matrix?
Cerebral cortex Amygdala Thalamus Hypothalamus Limbic system
