Which of the following tactile receptors respond to the vibration sense of 30 - 800 Hz?
Ans. A. Pacinian corpuscles. (Ref. Guyton Physiology 11th/pg. 587; Ganong 23rd/pg. 121-127, 746)Guyton Physiology 11th/pg. 587........."Detection of Vibration: All tactile receptors are involved in detection of vibration, although different receptors detect different frequencies of vibration. Pacinian corpuscles can detect signal vibrations from 30 to 800 cycles per second because they respond extremely rapidly to minute and rapid deformations of the tissues, and they also transmit their signals over type Ab nerve fibers, which can transmit as many as 1000 impulses per second. Low-frequency vibrations from 2 up to 80 cycles per second, in contrast, stimulate other tactile receptors, especially Meissner's corpuscles, which are less rapidly adapting than pacinian corpuscles". The Ruffini ending is a tonic receptor that produces a train of action potentials proportional to the intensity of pressure applied to the skin.Free nerve endings:# found everywhere in the skin and in many other tissues# Can detect touch and pressure.# For instance, even light contact with the cornea of the eye, which contains no other type of nerve ending besides free nerve endings, can nevertheless elicit touch and pressure sensations.Meissner fs corpuscle:# It is a touch receptor with great sensitivity is the Meissner's corpuscle# It is an elongated encapsulated nerve ending of a large (type Ab) myelinated sensory nerve fiber.# Present in the nonhairy parts of the skin and are particularly abundant in the finger- tips, lips, and other areas of the skin where one's ability to discern spatial locations of touch sensations is highly developed.# Meissner's corpuscles adapt in a fraction of a second after they are stimulated, which means that they are particularly sensitive to movement of objects over the surface of the skin as well as to low- frequency vibration.Merkel's discs:# Merkel's discs are often grouped together in a receptor organ called the Iggo dome receptor, which projects upward against the underside of the epithelium of the skin. This causes the epithelium at this point to protrude outward, thus creating a dome and constituting an extremely sensitive receptor.# Also note that the entire group of Merkel's discs is innervated by a single large myelinated nerve fiber (type Ab).# These receptors, along with the Meissner's corpuscles, play extremely important roles in localizing touch sensations to specific surface areas of the body and in determining the texture of what is felt.Hair end-organ:# Slight movement of any hair on the body stimulates a nerve fiber entwining its base. Thus, each hair and its basal nerve fiber, called the hair end-organ, are also a touch receptor.# This receptor adapts readily and, like Meissner's corpuscles, detects mainly- (a) movement of objects on the surface of the body or- (b) initial contact with the body.Ruffini's end-organs:# Located in the deeper layers of the skin and also in still deeper internal tissues are many Ruffini's end-organs, which are multibranched, encapsulated endings.# These endings adapt very slowly and, therefore, are important for signaling continuous states of deformation of the tissues, such as heavy prolonged touch and pressure signals.# They are also found in joint capsules and help to signal the degree of joint rotation.Pacinian corpuscles:# lie both immediately beneath the skin and deep in the fascial tissues of the body.# They are stimulated only by rapid local compression of the tissues because they adapt in a few hundredths of a second.# Therefore, they are particularly important for detecting tissue vibration or other rapid changes in the mechanical state of the tissues.
Pacinian corpuscles
Ruffini ending
Merkel's disk
Meissner's corpuscles
Nervous System