A ns. a (Rapidly adapting receptors); (Ref Ganong, Physiology, 21st ed., 125)MECHANORECEPTORSFour types of mechanoreceptors have been identified in glabrous skin, two in the superficial layers (Meissner's corpuscles and Merkel discs) and two in the subcutaneous tissue (Ruffini endings and Pacinian corpuscles). Light touch appears to have rapidly adapting while spindle and nociceptors are slowly adapting receptors.SENSORY CORPUSLESMeissner'sSmall, encapsulated nerve endings found in dermis of palms, soles and digits of skin.Involved in light discriminatory touch of glabrous (hairless) skin. Meissner's corpuscles are rapidly adapting mechanoreceptors, meaning that they respond only during the onset of skin stimulation. They respond to stroking and fluttering types of tactile stimuli.PacinianLarge,encapsulated nerve endings found in deeper layers of skin at ligaments, joint capsules, serous membranes, mesenteries. Involved in pressure, coarse touch, vibration and tension. Pacinian corpuscles are rapidly adapting and respond to high frequency vibrations.Merkel'sCup-shaped nerve endings (tactile discs) in dermis of fingertips, hair follicles, hard palate.Involved in light, crude touch. Merkel disc receptors are slowly adapting receptors, responding at constant discharge rates during constant intensity stimulation. Merkel disc receptors respond to pressure and texture.Ruffini endingsare slowly adapting receptors that respond to skin stretch.