Vibrations are felt by ?

Ans. is 'c' i.e., Pacinian corpuscle Tactile (touch) receptors These are general exteroreceptors for epicritic senses. These are divided into superficial and deep receptors. Superficial receptors are present in the epidermis or papillary layer of dermis. In glabrous (nonhairy) skin these receptors are Merkel's disc (slowly adapting) and Meissner 's corpuscle (rapidly adapting). In hairy skin there are hair follicle receptors. Deep receptors are present in deeper dermis or in the subcutaneous tissues. The deep receptors are same in both hair and nonhairy skin and include Ruffini's end organ (slowly adapting) and Pacinian corpuscle (Rapidly adapting). Touch, pressure and vibration are different forms of same sensation. Pressure is felt when the force applied on the skin is sufficient to reach the deep receptors, whereas touch is felt when the force is insufficent to reach the deep receptors, therefore detected by superficial receptors (Merkel's disc, meissner's corpuscle). Vibrations are rhythmic variations in pressure (i.e. rhymic variations of force that reaches the deep receptors). Whether a tactile receptor senses pressure or vibration depends on whether the receptor is slowly adapting or slowly adaping :? i) Slowly adapting (Ruffini's end organ) :- Are meant to detect sustained pressure; they are useless for vibrations. ii) Rapidly adapting (Pacinian corpuscle) :- Stop discharge in response to sustained pressure; they are useful only when the pressure fluctuates rapidly, i.e. during vibrations. The higher the rate of adaptation of a receptor, the greater is the vibration frequency it can detect. Thus, tactile (touch) sensation can be divided into :? A) Superficial (generally considered as touch) :- Detected by Meissner 's corpuscle (detect texture of surface, i.e. rough or smooth) and Merkel's disc (detect two point discrimination). B) Deep i) Pressure (Deep touch) :- Detected by Ruffini's end organ. ii) Vibrations :- Detected by Pacinian corpuscle