Nociceptor

A nociceptor (from Latin nocere to harm ') - also known as Nozisensor or mistakenly referred to as Nozirezeptor - is a free sensory nerve ending that converts tissue damage or injury due to thermal, chemical or mechanical noxious substances into electrical signals ( action potentials ).

According to their axon diameter and its specific responsiveness to nociceptors can be divided into three groups:

The first two are further characterized by myelinated axons, the last group by non-myelinated fibers.

Nociceptors are present as free nerve endings in the dermis. Free nerve endings are distinguished by a peripheral terminal arborization. They have a fenestrated sheath of Schwann cells and have numerous varicosities ( swellings ) on. These are mainly in the vicinity of blood vessels, and mast cells. Some of them penetrate into the epidermis. You are responsible for the properties of the skin as a protective cover of the organism is crucial.

The density of the nociceptors in man is greater than that of all other skin receptors. Distribution on the body surface is relatively uniform. In addition, one finds nociceptors in the muscles in the area of the intestines and other locations inside of the body. In the human body are found in every tissue nociceptors except in brain and liver.

Apparently there is a specificity for thermal, mechanical or chemical stimuli. It applies to mammals as evidence that nociceptors are represented by so-called free nerve endings. The excitation occurs at high stimulus intensities in each one. It is characterized by little or no adaptation.

Substances that activate nociceptors, called algogen, these substances can cause pain. Algogene substances are, for example, serotonin, bradykinin, histamine, as well as potassium ions, and leukotrienes. In pain research also use formaldehyde.

Origin

Nociceptors go in embryonic development such as nerve tissue generally produced from the ectoderm.