somesthesis(redirected from somaesthesia)
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A general term for the somatic sensibilities aroused by stimulation of bodily tissues such as the skin, muscles, tendons, joints, and the viscera. Six primary qualities of somatic sensation are commonly recognized: touch-pressure (including temporal variations such as vibration), warmth, coolness, pain, itch, and the position and movement of the joints. These basic sensory qualities exist because each is served by a different set of sensory receptors (the sensory endings of certain peripheral nerve fibers) which differ not only in their sensitivities to different types of stimuli, but also in their connections to structures within the central nervous system.
The somatic sensory pathways are dual in nature. One major part, the lemniscal system, receives input from large-diameter myelinated peripheral nerve fibers (for example, those serving the sense of touch-pressure). The second major somatic pathway is called the anterolateral system. It receives input from small-diameter myelinated and unmyelinated peripheral nerve fibers carrying pain and temperature information. See Cutaneous sensation, Proprioception