EDUCATION PERFECT Pain Module 2 Flashcards
T/F the sensation of pain is non-discriminative.
True
What are the three things that the experience of pain depends on?
- Sensory coding of stimuli
- Motivational/affective component (whether brain wants to attend to the input signalling potentially damaging stimuli or is engages with other things)
- Cognitive/cultural component (When the brain has learnt not to bother with that type of input signalling potentially damaging stimuli)
What are pain receptors called?
Nocireceptors/nociceptors
T/F The sensory processing of the pain input in the brain cannot be significantly modulated by other brain systems.
False, the pain input can be affected by other brain inputs, hence why sometimes pain is not felt when there is an injury and the brain is distracted.
Which sensory nerve fibre classes does pain belong to?
A-delta and C-classes
Where do pain sensations originate from?
The specialised endings of nerve fibres, not from special receptor cells.
How many basic classes do nociceptors have and what are they called
4
Temperature
Mechanical stimuli
Mechanical and thermal stimuli
Thermal, mechanical and chemical stimuli
What are nocireceptors receptive to thermal, chemical and mechanical stimuli called?
Polymodal nocireceptors (AKA wide dynamic range nocireceptors)
What are polymodal nociceptors sensitive to?
Polymodal nociceptors are sensitive to thermal, mechanical, and chemical stimuli. They are also known as wide dynamic range nociceptors.
Nocireceptors respond to what type of stimuli?
They respond to the same type of stimuli as other cutaneous receptors but only at stimulus levels outside the normal range that can/will harm the organism.
What type of charge excites a nociceptor and what ion creates this charge?
They are excited by a positive charge, generally from Na+
What is the activation temperature for the TRPV1 channel?
The TRPV1 channel is activated at temperatures above 43°C.
Which TRPV channel is involved in pain sensations to hot temperatures and what is its activation temperature?
TRPV2 is involved in pain sensations to hot temperatures and is activated at 52°C.
Besides temperature, what other substances can activate the TRPV1 receptor?
The TRPV1 receptor can be activated by capsaicin (found in hot chilies), allyl isothiocyanate (found in mustard and wasabi), and allicin (found in garlic).
What sensations can be evoked by consuming capsaicin or allyl isothiocyanate?
Consuming capsaicin or allyl isothiocyanate can evoke hot burning pain sensations.
What happens when TRPV1 is activated?
Activation of TRPV1 leads to a painful, burning sensation of scalding heat and pain.
What is the consequence of opening the TRPV1 channel?
Opening of the TRPV1 channel leads to the influx of Ca++ ions, the release of Ca++ from internal stores, and subsequent effects on cellular processes.
Depolarization
When the membrane potential is positively charged.
What can the excess Ca++ released from the activation of TRPV1 cause?
it can be detrimental in the future by breaking down the cytoskeletal proteins and the degradation of mitochondria.
Why does some pain start off sharp and is then followed by a slow dull pain?
C-class fibres are unmyelinated and slower than A-delta class nerve fibres hence each would arrive at the CNS at different times.
Tissue injuries can cause the following changes at the site of damage.
Allodynia AND Primary hyperalgesia
What is Allodynia
when non-noxious/innocuous stimuli are now felt as painful.
What is Primary hyperalgesia
when pain stimuli are now felt more intensely.
Why do Allodynia and Primary hyperalgesia occur?
changes in the endings of the nociceptor nerve fibres from the damaged area of skin (due to chemicals released from the damaged skin acting on the endings of the nerve fibres).
Damage to tissues causes the release of?
inflammatory agents like histamine into the damaged tissue
What do the release of inflammatory agents like histamine into the damaged tissue cause?
dilation (swelling) of local blood vessels. A by-product of these effects is fluid leakage out of the blood vessels to cause swelling in the injured tissue.
What effect does the fluid accumulation and swelling have on the TRPV1 ion channel?
There is evidence that the stretch caused by local fluid accumulation and swelling can activate the TRPV1 ion channel.
