touch

=Touch=

toc Read here about a sensory capability and its treatment in the comprehension of scale.

=Overview= Touch, also called tactition or mechanoreception, is a perception resulting from activation of a vast variety of receptors, generally in the skin including hair follicles, but also in the tongue, throat, and mucosa.

=Lack Of Touch= The loss or impairment of the ability to feel anything touched is called tactile anesthesia.

Discriminative Touch
The dermis and epidermis are host to a set of sensors, The perception of pressure, vibration, and texture. This system relies on four different receptors in the skin. They are named Meissner and Pacinian corpuscles, Merkel disks and Ruffini endings: Molavi gives the following example of these receptors in operation: If you lay your pen down in your palm, the Meissner's and Pacinian corpuscles will fire rapidly as it first touches down, to let you know something has landed. If the pen lays still, they will stop firing almost right away. The Merkel's and Ruffini endings, however, will continue to fire to let you know that something is still there.
 * Type I cutaneous mechanoreceptor (tactile or Merkel disc): slowly adapting (do not stop firing)
 * Corpuscle of touch (Meissner corpuscle in dermal papilla): rapidly adapting (quickly stop firing in response to a constant stimulus)
 * Type II cutaneous mechanoreceptor (Ruffini corpuscle, or Ruffini ending): slowly adapting (do not stop firing)
 * Lemellated (Pacinian) corpuscle: rapidly adapting (quickly stop firing in response to a constant stimulus)
 * Hair root plexus

Major Classes of Somatic Sensory Receptors
Table of The Major Classes of Somatic Sensory Receptors
 * Receptor type||Anatomical characteristics||Associated axonsa (and diameters)||Axonal conduction velocities||Location||Function||Rate of adaptation||Threshold of activation||
 * Free nerve endings||Minimally specialized nerve endings||C, Aδ||2–20 m/s||All skin||Pain, temperature, crude touch||Slow||High||
 * Meissner's corpuscles||Encapsulated; between dermal papillae||Aβ 6–12 μm||||Principally glabrous skin||Touch, pressure (dynamic)||Rapid||Low||
 * Pacinian corpuscles||Encapsulated; onionlike covering||Aβ 6–12 μm||||Subcutaneous tissue, interosseous membranes, viscera||Deep pressure, vibration (dynamic)||Rapid||Low||
 * Merkel's disks||Encapsulated; associated with peptide- releasing cells||Aβ||||All skin, hair follicles||Touch, pressure (static)||Slow||Low||
 * Ruffini's corpuscles||Encapsulated; oriented along stretch lines||Aβ 6–12 μm||||All skin||Stretching of skin||Slow||Low||
 * Muscle spindles||Highly specialized (see Figure 9.5 and Chapter 15)||Ia and II||||Muscles||Muscle length||Both slow and rapid||Low||
 * Golgi tendon organs||Highly specialized (see Chapter 15)||Ib||||Tendons||Muscle tension||Slow||Low||
 * Joint receptors||Minimally specialized||—||||Joints||Joint position||Rapid||Low||