Human Body

Nerves and Senses

What are endorphins?

The British physiologists William Bayliss (1860–1924) and Ernest Starling (1866–1927) discovered secretin in 1902. They used the term “hormone” (from the Greek word horman, meaning “to set in motion”) to describe the chemical substance they had discovered that stimulated an organ at a distance from the chemical’s site of origin. Their famous experiment using anesthetized dogs demonstrated that dilute hydrochloric acid, mixed with partially digested food, activated a chemical substance in the duodenum (the upper part of the small intestine). This activated substance (secretin) was released into the bloodstream and came into contact with cells of the pancreas. In the pancreas it stimulated secretion of digestive juice into the intestine through the pancreatic duct.

Endorphins and closely related chemicals called enkephalins are part of a larger group called opiods, which have properties simliar to drugs such as heroin or morphine. They can act not only as pain killers but also can induce a sense of well-being or euphoria. Clinical applications of endorphin research include possible treatments for some forms of mental illness; treatment or control of pain for chronic pain sufferers; development of new anesthetics; and the development of non-addictive, safe, and effective pain relievers.


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