The structure and function of a slowly adapting touch corpuscle in hairy skin

TLDR

Slowly adapting cutaneous mechanoreceptors in cat and primate skin are dome-shaped epidermal elevations containing up to fifty Merkel cells that connect to a single myelinated axon, and have been studied histologically and neurophysiologically. The authors quantified responses of touch corpuscles to displacements of varying amplitude, velocity, and duration, noting an initial rapid adaptation followed by a sustained response lasting over 30 minutes. Touch corpuscles fired over 1000 impulses per second under vertical pressure, responded with a low threshold and frequency dependent on displacement velocity and amplitude, showed a rapid adaptation followed by a sustained response lasting >30 min, and their discharge was temperature‑sensitive, increasing when skin temperature fell. 1.

Abstract

1. Slowly adapting cutaneous mechanoreceptors, in the cat and primates, have been studied by histological and neurophysiological methods.2. Each touch corpuscle is a dome-shaped elevation of the epidermis, whose deepest layer contains up to fifty specialized tactile cells.3. Nerve plates, enclosed by the tactile cell (Merkel cells), are connected to a single myelinated axon in the dense collagenous core of the corpuscle.4. The corpuscle generated > 1000 impulses/sec when excited by vertical surface pressure. The response was highly localized and showed a low mechanical threshold, the frequency being dependent upon the velocity and amplitude of the displacement. There was a period of rapid adaptation before a sustained response which might continue for > 30 min.5. A quantitative analysis of the responses to excitation by displacements of differing amplitude, velocity and duration is included.6. The discharge of touch corpuscle units evoked by a mechanical stimulus was temperature-sensitive, and was enhanced by a fall in skin temperature.