Figure 1.

Touch receptors of hairy skin. A diverse group of mechanosensory afferents innervate the hairy skin of mammals. The schematic depicts anatomically distinct end organs (right), which give rise to neural signals with distinct patterns of activity (center). These different classes of sensory neurons initiate the perception of different cutaneous sensations (left). Aβ afferents (blue shades), which have thick myelin sheaths, are gentle-touch receptors that display rapidly adapting (RA) or slowly adapting (SA) responses to touch. In hairy skin, RA afferents form lanecolate endings around hair follicles. Slowly adapting type I (SAI) afferents innervate Merkel cells (yellow) clustered in touch domes. Aδ afferents (green shades), which have thin myelin sheaths, include Aδ low-threshold mechanoreceptors (LTMRs) and A-mechanonociceptors (AM), whose morphological end organs have not been identified. C-afferents (magenta shades) include C-LTMRs that innervate hair follicles as well as pruritoceptors and nociceptors that innervate the epidermis. (Modified from Bautista and Lumpkin 2011.)