[1] There are four subdivisions of group A nerve fibers: alpha (α) Aα; beta (β) Aβ; , gamma (γ) Aγ, and delta (δ) Aδ.
Larger diameter axons and more myelin insulation lead to faster signal propagation.
However a small fraction of these fast fibres, termed "ultrafast nociceptors", also transmit pain.
Aδ fibers carry information from peripheral mechanoreceptors and thermoreceptors to the dorsal horn of the spinal cord.
Within the spinal cord the axons reach the posterior grey column and terminate in Rexed laminae I to V.[10]