Mechanoreceptors of the skin
There are specialized receptors in the skin that are excited by mechanical stimuli such as stretching and pressure. These mechanoreceptors in the skin are primary sensory cells , which means that an axon of its own directs impulses towards the central nervous system . In humans, there are four classes of mechanoreceptors in the skin. They transmit all of their impulses via Aß-fibers (relatively fast conducting myelinated nerve fibers ).
Classification
One differentiates:
- SA-I (slowly adapting 1)
- SA-II (slowly adapting 2)
- RA (rapidly adapting)
- PC (Pacinian Corpuscle)
SA-I receptors
These are slowly adapting mechanoreceptors that continuously generate action potentials in response to a long-term stimulus (e.g. the body weight that is placed on the sole of the foot when standing) . They speak mainly to vertical stimuli, i. H. on push and pull. The histological correlate of the SA-I receptors are the Merkel tactile disks in the stratum basale of the epidermis .
SA-II receptors
They too slowly adapt to stimuli, but mainly code for stretching the skin. They are located in the reticular stratum of the dermis and are histologically described as Ruffini bodies .
RA receptors
The rapidly adapting mechanoreceptors only fire when there is movement or changes in the stimulus strength. So they are speed receptors. They are the Meissner corpuscles in the stratum papillare of the dermis. There are no Meissner bodies in the hairy skin. The hair follicle sensors take over their function .
PC receptors
These receptors adapt the fastest. They only show changes in the speed of a stimulus ( acceleration ). These receptors include the Vater-Pacini corpuscles of the subcutis and the Krause end pistons of the dermis .