Cutaneous touch receptors. Mechanosensory afferents innervating mammalian skin display morphological and functional diversity. Cartoons depict end-organs in hairy skin (left) and glabrous skin (right), although innervation density is not meant to be representative. For physiologically defined afferent classes, typical action potential trains evoked by touch stimuli are schematized (center). Thickly myelinated Aβ afferents (blue shades) are touch receptors that display RA or SA responses to mechanical stimuli. RA afferents innervate hair follicles, Pacinian corpuscles, and Meissner’s corpuscles. SAI afferents innervate epidermal Merkel cells (yellow), and SAII afferents are thought to innervate Ruffini endings. Thinly myelinated Aδ afferents (green shades) include down-hair afferents and A-mechanonociceptors. C-afferents (red and magenta), which surround hair follicles (Park et al., 2003) and abundantly innervate the epidermis, include peptidergic nociceptors, nonpeptidergic nociceptors, and C low-threshold mechanoreceptors.