Cutaneous, Kinesthetic and Visceral Sensitivity

The skin contains several different types of simple sensory organs some of them are simply free ends of dendrites, others are ends of dendrites enclosed in special cell capsules. When a small area of ​​skin was carefully examined, point by point, using a stiff bristle (to test the sense of touch) and a hot or cold metal needle (to test the sense of temperature), it turned out that the receptors for each of these sensations were located at different points. By comparing the distribution of different types of terminal sensory organs and the types of sensations caused, it was established that free nerve endings are responsible for the feeling of pain, and certain types of encapsulated endings are responsible for other sensations.

Kinesthetic sensitivity. All muscles, tendons and joints are equipped with nerve endings called proprioceptors, which are similar to some receptors in the skin. These endings are sensitive to changes in the tension of a muscle or tendon and send impulses to the brain, thanks to which we feel the position and movement of various parts of the body. This feeling is called kinesthetic it gives us the opportunity, even with our eyes closed, to perform various actions with our hands, for example, getting dressed or tying knots. In addition, impulses from proprioceptors are extremely important for the coordinated reduction of the work of all other receptors in fact, the existence of kinesthetic sensitivity was only discovered about 100 years ago.

Visceral sensitivity. Sensations associated with the receptors of the internal organs, which are extremely important for regulating the functioning of the internal organs, rarely reach the level of consciousness. They carry out reflex regulation of the functions of internal organs through reflex centers in the medulla oblongata, midbrain or thalamus. Some impulses from these receptors, however, reach the cerebral cortex and cause sensations such as thirst, hunger or nausea.

The feeling of thirst occurs when receptors in the mucous membrane of the pharynx are irritated when this shell dries out, the receptors send impulses to the brain, which we interpret as a feeling of thirst. The stomach wall also contains receptors. When the stomach is empty, a series of strong, slow muscle contractions pass through its walls, stimulating the receptors and causing a feeling of hunger.

The feeling of fullness and the need to defecate and urinate depends on receptors in the walls of the rectum and bladder, stimulated by the distension of these hollow organs by their contents. Many other, less specific visceral sensations occur during sexual activity, illness or emotional crises.