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Touch is mediated by four types of mechano receptors in the human hand. The terminals of myelinated sensory nerves innervating the hand are
surrounded by specialized structures that detect contact on the skin. The receptors differ in morphology, innervation patterns, location in the skin, receptive
field size, and physiological responses to touch. (Adapted, with permission, from Johansson and Vallbo 1983.)
A. The superficial and deep layers of the glabrous (hairless) skin of the hand each contain distinct types of mechanoreceptors. The superficial layers
contain small receptor cells: Meissner corpuscles and Merkel cells. The sensory nerve fibers innervating these receptors have branching terminals such
that each fiber
innervates
multiple receptors
of oneReceptors
type. The deep
layers of
the skin and
subcutaneous
contain
receptors: Pacinian corpuscles
Source:
The Somatosensory
System:
and Central
Pathways,
Principles
of Neuraltissue
Science,
Fifthlarge
Editon
and Ruffini endings. Each of these receptors is innervated by a single nerve fiber, and each fiber innervates only one receptor. The receptive field of a
Citation: Kandel ER, Schwartz JH, Jessell TM, Siegelbaum SA, Hudspeth AJ, Mack S. Principles of Neural Science, Fifth Editon; 2012 Available
mechanoreceptor reflects the location and distribution of its terminals in the skin. Touch receptors in the superficial layers of the skin have smaller
at: http://mhmedical.com/ Accessed: May 11, 2017
receptive fields than those in the deep layers. (RA1, rapidly adapting type 1; RA2, rapidly adapting type 2; SA1, slowly adapting type 1; SA2, slowly
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adapting type 2.)