Functions of Mechanoreceptors in the Skin

‭Functions of Mechanoreceptors in the Skin‬ ‭-Ruffini corpuscle:‬ ‭ Is different from the previous ones not so much by its location because also in the dermis and‬ ✪ ‭hypodermis and it is common at the soles of the feet, it is an elongated structure but there is no‬ ‭Schwann cell, it is actually associated with fibers of collagens and it is also surrounded by a‬ ‭capsule.‬ ‭ Here again there is a myelinated nerve fiber which will approach the Ruffini corpuscle through its‬ ✪ ‭middle part, its middle part and which will very quickly lose its myelin sheath first and then become‬ ‭arborized and these numerous ramifications are located between collagen fibers therefore the‬ ‭central part, this are no longer Schwann cells but they are collagen fibers more or less intertwined‬ ‭with each other, more or less thick, it is these collagen fibers which form the center of the corpuscle‬ ‭and which will fuse beyond with the collagen fibers of the dermis so there is a certain continuity‬ ‭between the collagen fibers of the dermis and those which are densifies inside this Ruffini‬ ‭corpuscle. The fiber is not dreamer and is stimulated by the movement of collagen fibers so it is‬ ‭also a mechanoreceptor which has a rapid adaptation and slow response.‬ ‭ There are other corpuscles such as the Krause corpuscle located in the dermis with a very thin‬ ✪ ‭capsule, with a myelinated afferent fiber, which ends, which loses its myelin sheath, which branches‬ ‭and there is the Golgi corpuscle etc...‬ ‭-Synthesis on this innervation:‬ ‭ Indeed, we saw different elements. The information received at the cutaneous level is multiple:‬ ✪ ‭thermal, painful, fine touch, coarse touch and therefore all these structures, whether the free endings‬ ‭or the different corpuscles, will make it possible to capture this information. The touch is mediated‬ ‭by two types of mechanoreceptor: those which have a slow adaptation (= as long as the stimulation‬ ‭lasts or almost) and those which have a rapid adaptation (= an activity at the beginning of the‬ ‭stimulation then it stops very quickly even if the stimulation persists). Pain is a receptors that we‬ ‭call nociceptive, therefore capable of detecting painful sensations, they are generally small nerve‬ ‭fibers and there we have 3 types of receptors for pain: so-called nociceptive mechanoreceptors‬ ‭which sense pain and which generally sense pain produced by sharp objects.‬ ‭ There are nociceptive thermoreceptors which are activated by temperatures above 45° and there‬ ✪ ‭are receptors which are multi polymodal and therefore respond to all kinds of painful sensations.‬ ‭Thermal sensitivity is ensured by heat receptors and cold receptors but within certain limits: cold‬ ‭receptors respond optimally roughly between 10 and 30° and heat receptors.r respond to‬ ‭temperatures between 35 37° and 45°, beyond this it is no longer a thermal sensitivity but it is a‬ ‭painful sensitivity. All these receptors which are multiple are not in their intimate mechanisms well‬ ‭known in the sense that we know that activation cellular is direct, there is no second messenger for‬ ‭example therefore a latency time between the stimulus and the very weak nervous impulse of the‬ ‭order of a few ms and in fact what is the receptor is the nerve fiber and the corpuscle itself is a sort‬ ‭of amplifier which increases the signal but what receives the signal is the nerve fiber which is in the‬ ‭center or which is arborized.‬