Pain Flashcards
Four types of sensory receptors
Thermoreceptors
Mechanoreceptors
Chemoreceptors
Nociceptors
Thermoreceptors
Monitor temperature (cold OR warm, not both)
Located in the skin and in some parts of the CNS (hypothalamus and spinal cord)
Help maintain stable body temperature
Mechanoreceptors
Monitor changes in the distortion of the cell membrane (e.g. stretching, bending)
Three sub types of Mechanoreceptors
- tactile receptors → touch, pressure, vibration
- baroreceptors → pressure in blood vessels and viscera
- proprioceptors → position of skeletal muscles and joints
Tactile receptors
Meissner’s corpuscles (touch, pressure, vibration)
Merkel’s cells (touch, pressure)
Pacinian corpuscles (deep pressure, vibration)
Ruffini corpuscles (deep pressure, vibration)
Different receptors, in addition to the type of the stimulus they respond to, differ according to the size of the receptive fields and to the rate of adaptation.
Located beneath skin.
Baroreceptors
Monitors changes in pressure;
Found in blood vessels, heart…(not on the skin!)
Free nerve endings
Proprioceptors
3 types → joint capsule receptors,
muscle spindles (muscle length),
Golgi tendon organs (muscle tension)
Know our position in space in real time.
Chemoreceptors
Monitor changes in the concentration of chemicals.
Spicy flavours are an unpleasant chemical sensation.
Nociceptors
Detect potential or actual tissue damage (thermal, mechanical, polymodal)
Found in skin, bones, skeletal muscles, less common in visceral tissues and organs
Free nerve ending
You can have a response to a noxious stimulus/nociception even without pain, and you can have pain without a noxious stimulus/nociception, i.e. ‘pain’ is a conscious experience, nociception is not.
What is pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
At least in part cognitively mediated.
Pain can be influenced by attitudes and beliefs, pain escape behaviour, and social environment. Spinal cord can also generate unnecessary warning signals.
Pain can be learned.
Why do we need pain?
Avoid tissue damage.
Know when to rest.
Ronald Melzack – neuromatrix theory (NMT)
Neural networks that work together → specific output = neurosignature
Therefore “neurosignature” for pain, producing:
Perception
Behavioural response
Hebbian concept
networks based on the Hebbian concept of “fire together, wire together”:
The more a network is used, the stronger it becomes.
We can think of “neurosignatures” as graffiti tags - NEUROTAGS
Action Neurotags
Action NTs (influence outside the brain), e.g. sight
= what you see
Action neurotags promote protection and regulation by affecting pain, movement or immune response
Modulation Neurotags
Modulation NTs (influence within the brain), e.g. visually encoded data
= your visual perception
Modulatory neurotags influence the Action neurotags with different level of strength.
Pain conditioning paradigm
(a) acquisition phase:
CS+: 1 non painful vibrotactile stimulus paired with 1 painful laser stimulus;
CS-: 1 non painful vibrotactile stimulus paired with 1 non painful laser stimulus.
(b) Test phase:
At-pain-threshold laser stimuli delivered simultaneously with a CS+ or CS- vibrotactile stimulus.
After conditioning, at-threshold laser trials paired with the CS+ were reported as painful more often, as more intense, and as more unpleasant than those paired with the CS-.
Cortical body matrix
Cortical representation
Audition
Vision
Skin receptors
Vestibular system
Muscle spindle and Golgi tendon organs
Feeling of less danger may result in less pain, feeling of more danger may result in more pain.
