Which of the following are the slowly adapting mechan- oreceptors present in the skin that are very sensitive to perpendicular indentation?
Ans. c (Merkel discs). (Ref. Ganong Physiology 21st ed., 125)MECHANORECEPTORS# Four types of mechanoreceptors in glabrous skin are-two in the superficial layers (Meissner's corpuscles and Merkel discs) and two in the subcutaneous tissue (Ruffini endings and Pacinian corpuscles).Meissner's corpuscles# are rapidly adapting mechanoreceptors# respond to Low frequency vibrations, stroking and fluttering types of tactile stimuli.Merkel disc receptors# are slowly adapting receptors# respond to pressure and texture.Pacinian corpuscles# are rapidly adapting and# respond to high frequency vibrations.Ruffini endings# are slowly adapting receptors that respond to skin stretch.# These endings link subcutaneous tissue to skin folds overlying joints.The afferent fibres of these receptors are myelinated and include:# large (group A alpha),# medium (group Ab),# small (group Adelta) diameter fibres.# Smallest (group A gama)- Tactile sensitivity is greatest on the glabrous (hairless) skin of the hands, the soles of the feet, and the lips.
Pacinian corpuscles
Meissner's corpuscles
Merkel discs
Ruffini end organs
Nervous System