Meissner corpuscles have large, myelinated axons associated with rapid-adapting type 1 receptors.
FUNCTION OF FREE NERVE ENDINGS IN SKIN SKIN
Meissner’s corpuscles have a “coin stack” morphology and facilitate the detection of low-frequency vibrations, fine touch, and fine dynamic skin movement. Meissner’s corpuscles are located in the dermal papillae of non-hairy (glabrous) skin. Ruffini endings are associated with slow-adapting type 2 receptors. Ruffini endings facilitate the detection of stretch, slipping, or sliding of objects across the skin surface and joint angle changes. Ruffini nerve endings (or Ruffini corpuscles) are concentrated at the fingertips but are located throughout the dermis as well as in joints and fascia. Merkel discs are associated with slow-adapting type 1 receptors. Merkel’s discs facilitate the detection of pressure, static touch, corners, edges, curvatures, and position sense. They are heavily concentrated at the fingertips and basal layer of the epidermis and have large myelinated axons. Merkel discs are found in both hairy and non-hairy (glabrous) skin. Four main types of receptors are responsible for sensing light pressure, firm pressure, dynamic pressure, vibration, and relative position. Non-painful mechanical stimuli compose the sense of touch via low-threshold mechanoreceptors. Mechanoreceptors (Pressure, Vibration, and Proprioception)
Cellular Levelĭifferent receptor types and free nerve endings, each with their own specific function, generate the overall sense of touch, position in space, and pain. For the purposes of this article, “mechanoreceptor” refers to the mechanosensory end-organ structure and its associated low-threshold mechanoreceptor (LTMR). Based on these different pathways, the clinical picture of patients presenting with sensory abnormalities can help elucidate the suspected location of a spinal cord or central lesion based on the anatomical region and the type of sensation affected. This article is focused on the discussion of the general senses.īoth innocuous and harmful mechanical and thermal stimuli are processed by different receptors and nerve fiber types in the skin, follow specific ascending pathways through the spinal cord (dorsal column or spinothalamic tract), and eventually relay to the somatosensory cortex. Special senses are processed via cranial nerves and differ from the pathway utilized in processing general senses. Special senses include vision, hearing, taste, and smell. General senses include touch, pain, temperature, proprioception, vibration, and pressure. īroadly, sensations fall into two categories: General and special senses. Various sensory perceptions then influence voluntary and involuntary motor activity to facilitate interaction with the world. The sensory system receives and processes information that generates an individual's awareness of their environment.
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