#NUMBER OF NERVE ENDINGS IN FEET SKIN#
Cutaneous mechanoreceptors localize in different layers of the skin with varying ranges of mechanical stimuli detection. Mechanoreceptors will respond to vibrations, indentations of the skin, or movement of hair follicles. įor tactile receptors used for touch, there is precise coding of mechanical information. Two weeks postnatal age, mechanoreceptive neurons are not fully mature, but several types of A afferents can be present in ex vivo electrophysiology preparations. This finding means mechanoreceptive neurons acquire a sensitivity to touch soon after specification but require postnatal maturation for adult physiological properties. The thinking is that these factors enhance the specification of mechanosensory neurons by maintaining the expression of neurotrophin receptors Ret and Gfra2. Transcription factors that specify mechanoreceptors include MafA and c-Maf. These neurons will become either: low-threshold mechanoreceptors or proprioceptors. In early embryonic days (9.5 to 11.5 days), neurons express Ngn2 and include A-beta and A-delta afferents with large-diameter cell bodies and myelinated axons. All somatosensory neurons require the expression of neurogenin 1 or 2 ( Ngn1/2). The temporal waves of cell fate specification first establish the somatosensory neurons heterogeneity. As the embryo grows from day 9.5 to 12.5, a subset of neural crest cells gives rise to somatosensory neurons that form pairs of dorsal root ganglions (DRGs) located in the intervertebral foramina for each spine level.
Somatosensory neurons arise from neural crest cells.
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