sensepäät

Sensepäät (sensory endings) are the terminal structures of sensory neurons that detect environmental stimuli and relay information to the central nervous system. They are widely distributed, especially in the skin and mucous membranes, but also in muscles and joints, where they transduce mechanical, thermal, chemical, or nociceptive stimuli into electrical signals.

Structural types include free nerve endings, which are unspecialized endings involved in pain and temperature detection, and encapsulated endings that provide more specialized sensing. Examples of encapsulated endings are Merkel discs (slowly adapting touch receptors in the epidermis), Meissner’s corpuscles (light touch in glabrous skin), Pacinian corpuscles (deep pressure and vibration, rapidly adapting), and Ruffini endings (skin stretch, slowly adapting). Hair follicle receptors detect movement of hairs and contribute to tactile sensation.

Physiologically, sensepäät support mechanoreception, thermoreception, and nociception. They convey information via different peripheral nerve fibers, including A-delta fibers for fast, sharp pain and cold, and C fibers for slow, dull pain and warmth. The generated action potentials travel along afferent axons to the spinal cord or brainstem, where they are relayed to higher brain regions for conscious perception.

Adaptation properties vary among endings: rapidly adapting receptors respond briefly to changes in stimulus, while slowly adapting receptors maintain firing during sustained stimuli, contributing to continued perception of touch, pressure, or stretch.

Developmentally, peripheral sense endings arise from sensory neurons derived from neural crest cells, with specialized endings forming in association with skin, connective tissue, and associated glial cells. Loss or dysfunction of sensepäät can affect touch, temperature, and pain perception, influencing safety and motor coordination.