Property

C-fibre

A(delta)-fibre

A(beta) fibre

Neuronal size

Small- 0.4±1.2 mm

Medium- 2±6 mm

Large->10 mm

Conduction velocity

Slow- unmyelinated - 2 m/s

Fast- myelinated- 20 m/s [C1]

Fast- myelinated- 30±100 m/sec

Adaption rate

Threshold for activation

High

High

High

Termination in spinal cord laminae

Laminae I & II, and then projects to V (polysynaptic)

Laminae I & V (monosynaptic)

Laminae I & II & V >> not very well studied

Sensation

Poorly localised [C2] - Burning pain

Well localised [C3] - Sharp pain

Sharp pain

modality

thermal, mechanical, and chemical stimuli- polymodal

dangerously intense mechanical or to mechanothermal stimuli

Receptive field

Relatively large- presumably because the detection of pain is more important than its precise localization

Relatively large- clusters of sensitive spots

[C1]That a proportion of A-fibre nociceptive neurones have fibres that conduct in the Aa/b range has been confirmed with intracellular recordings in DRG neurones in vivo in several species.

[C2]effective in causing reflex changes such as cardiovascular or respiratory changes

[C3]important property of an exteroceptive pathway, enabling precise and rapid withdrawal responses from a specific localised noxious stimulus

	Created by Cher Bachar over 11 years ago

Neuroscience of Pain Note on Pain- general, created by Cher Bachar on 17/05/2013.