PHYS Pain & Temperature Sensation

Question 1

What do Merkel’s discs convey?

Answer 1

Pressure & gentle touch.

Question 2

What do Meissner’s corpuscles convey?

Answer 2

Light touch.

Question 3

What do Pacinian corpuscles convey?

Answer 3

Vibration, pressure.

Question 4

What do hair follicle receptors convey?

Answer 4

Touch.

Question 5

What do Ruffini’s endings convey?

Answer 5

Stretch.

Question 6

What do free nerve endings convey?

Answer 6

Pain & temperature.

Question 7

What do free nerve endings convey?

Answer 7

Pain & temperature.

Question 8

Where are free nerve endings located?

Answer 8

Everywhere outside of CNS.

Question 9

What type of pain are C receptors responsible for?

Answer 9

Slow ‘groaning’ pain.

Question 10

What type of pain are A-delta fibres responsible for?

Answer 10

Fast ‘outch’ pain.

Question 11

Primary hyperalgesia.

Answer 11

Region of injury is hypersensitive.

Question 12

Secondary hyperalgesia.

Answer 12

Surrounding area is also sensitised.

Question 13

Allodynia.

Answer 13

Non-noxious stimuli is now painful.

Question 14

What is the main pathway carrying nociceptive information to the brain?

Answer 14

Anterolateral/spinothalamic.

Question 15

What information is carried by the anterolateral tract?

Answer 15

Crude touch & itch - anteriorly
Temperature, sexual sensation & nociception - laterally.

Question 16

VPL vs VPM

Answer 16

Ventral posterior lateral nuclei (VPL) receives nociceptive information from the body.
Ventral posterior medial nuclei (VPM) receives bulk of nociceptive information from the face.

Question 17

Sub-categories of C-fibres & details of what stimuli they each respond to.

Answer 17

• 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).

Question 18

Sub-categories of A-delta fibres with details of responding stimuli & heat/mechanical thresholds.

Answer 18

• 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.

Question 19

Classifications of C fibres - state what they release/express/detect.

Answer 19

• 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.

Question 20

What do A-alpha fibres detect? beta, delta, c?

Answer 20

Proprioception.
Touch.
Pain & temperature.
Pain.