PHYS Pain & Temperature Sensation Flashcards
What do Merkel’s discs convey?
Pressure & gentle touch.
What do Meissner’s corpuscles convey?
Light touch.
What do Pacinian corpuscles convey?
Vibration, pressure.
What do hair follicle receptors convey?
Touch.
What do Ruffini’s endings convey?
Stretch.
What do free nerve endings convey?
Pain & temperature.
What do free nerve endings convey?
Pain & temperature.
Where are free nerve endings located?
Everywhere outside of CNS.
What type of pain are C receptors responsible for?
Slow ‘groaning’ pain.
What type of pain are A-delta fibres responsible for?
Fast ‘outch’ pain.
Primary hyperalgesia.
Region of injury is hypersensitive.
Secondary hyperalgesia.
Surrounding area is also sensitised.
Allodynia.
Non-noxious stimuli is now painful.
What is the main pathway carrying nociceptive information to the brain?
Anterolateral/spinothalamic.
What information is carried by the anterolateral tract?
Crude touch & itch - anteriorly
Temperature, sexual sensation & nociception - laterally.
VPL vs VPM
Ventral posterior lateral nuclei (VPL) receives nociceptive information from the body.
Ventral posterior medial nuclei (VPM) receives bulk of nociceptive information from the face.
Sub-categories of C-fibres & details of what stimuli they each respond to.
• Nociceptive
o Polymodal - responding to both noxious heat & mechanical stimuli
• Silent
o Heat-responsive
o Mechanically insensitive
o Respond to chemical stimuli (e.g., capsaicin) -> unsilenced
o Develop mechano-sensitivity in response to injury -> unsilenced
o Play a role in inflammation -> mechanical hyperalgesia development.
• Itch
o Respond to ‘itch’ initiating chemical irritants (e.g., histamine)
• Non-nociceptor
o Some respond to cold or cooling stimuli
o Some respond to harmless stroking of ‘hairy skin’ (unresponsive to heat/chemical stimuli).
Sub-categories of A-delta fibres with details of responding stimuli & heat/mechanical thresholds.
• Type I (High-threshold Mechanical Receptors (HTMRs))
o Respond to chemical & mechanical stimuli
o Relatively high heat threshold (>50oC)
o Mediate first response to pin prick/intense mechanical stimuli.
o Display sensitisation (e.g., if heat stimulus persists, heat & mechanical threshold reduces).
• Type II (thermal)
o Lower heat threshold
o Higher mechanical threshold
o Mediates ‘first’ or ‘fast’ acute pain response to noxious heat.
Classifications of C fibres - state what they release/express/detect.
• Peptide-expressing
o Release Substance P and Calcitonin Gene-Related Peptide (CGRP)
o Express TrKA receptor – detects Nerve Growth Factor (NGF)
• Non-peptide-expressing/non-peptinergic
o Express C-Ret neurotrophin receptor – detects glial-derived neurotrophic factor (GDNF)
o Expresses P2X3 receptors.
What do A-alpha fibres detect? beta, delta, c?
Proprioception.
Touch.
Pain & temperature.
Pain.
