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Merkel nerve endings (also Merkel's disks,[1] or Merkel tactile endings[2]) are mechanoreceptors situated in the basal epidermis as well as around the apical ends or some hair follicles.[2] They are slowly adapting They have small receptive fields measuring some milimeters in diameter. Most are associated with fast-conducting large myelinated axons.[1] A single afferent nerve fibre branches to innervate up to 90 such endings.[citation needed] Merkel nerve endings respond to light touch.[1] They respond to sustained pressure, and are sensitive to edges of objects. Their exact functions remain controversial.[2]
The Merkel nerve endings consist of a nerve ending associated with a flattened epithelial cell (Merkel cell); both the nerve ending and Merkel cell are independently mechanosensitive. The Merkel cell expresses the PIEZO2 mechanosensitive ion channels; mechanical activation of the channel causes depolarisation of the Merkel cell and consequent release of[1] serotonin into a synapse with the associated nerve ending, to also depolarise the later.[3] The nerve ending meanwhile expresses an unknown mechanosensitive channel.[1]
- ^ a b c d e Bear, Mark F.; Connors, Barry W.; Paradiso, Michael A. (2016). Neuroscience: Exploring the Brain (4th ed.). Philadelphia: Wolters Kluwer. pp. 417, 418, 420. ISBN 978-0-7817-7817-6.
- ^ a b c Standring, Susan (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42th ed.). New York: Elsevier. pp. 63–64. ISBN 978-0-7020-7707-4. OCLC 1201341621.
- ^ Chang, Weipang; Kanda, Hirosato; Ikeda, Ryo; Ling, Jennifer; DeBerry, Jennifer J.; Gu, Jianguo G. (13 September 2016). "Merkel disc is a serotonergic synapse in the epidermis for transmitting tactile signals in mammals". Proceedings of the National Academy of Sciences. 113 (37). doi:10.1073/pnas.1610176113. PMC 5027443.