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Cutaneous mechanoreceptors can also be separated into categories based on their rates of adaptation. When a mechanoreceptor receives a stimulus, it begins to fire impulses or action potentials at an elevated frequency (the stronger the stimulus, the higher the frequency). The cell, however, will soon "adapt" to a constant or static stimulus ...
Aδ fibers are characterized by thin axons and thin myelin sheaths, and are either D-hair receptors or nociceptive neurons. Aδ fibers conduct at a rate of up to 25 m/s. D-hair receptors have large receptive fields and very low mechanical thresholds, and have been shown to be the most sensitive of known cutaneous mechanoreceptors.
Tactile perception is achieved through the response of mechanoreceptors (cutaneous receptors) in the skin that detect physical stimuli. The response from a mechanoreceptor detecting pressure can be experienced as a touch, discomfort, or pain. [23] Mechanoreceptors are situated in highly vascularized skin, and appear in both glabrous and hairy skin.
Sensory receptors can receive stimuli from outside the body, as in touch receptors found in the skin or light receptors in the eye, as well as from inside the body, as in chemoreceptors and mechanoreceptors. When a stimulus is detected by a sensory receptor, it can elicit a reflex via stimulus transduction.
Typically the mechanical stimulus gets filtered in the conveying medium before reaching the site of mechanotransduction. [11] Cellular responses to mechanotransduction are variable and give rise to a variety of changes and sensations. Broader issues involved include molecular biomechanics.
The initialization of sensation stems from the response of a specific receptor to a physical stimulus. The receptors which react to the stimulus and initiate the process of sensation are commonly characterized in four distinct categories: chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors.
The two different types of mechanoreceptor in the skin are termed low-threshold mechanoreceptors, and high threshold mechanoreceptors. The four mechanoreceptors in glabrous skin are low-threshold that respond to harmless stimuli. They are innervated by four different afferent fibers. High-threshold mechanoreceptors, respond to harmful stimuli. [7]
Stretch-activated ion channels are required for the initial formation of an action potential from a mechanical stimulus, for example by the mechanoreceptors in vibrissae (whiskers) of some animals such as rodents. Afferent nerve fibers responsible for sensory stimulus detection and feedback are especially sensitive to stimulation.