Endogenous morphine, coined by the morphing of the two descriptive terms into endorphins, are opioid neuropeptides which are naturally produced in the body that serve a primary function as an agent blocking the perception of pain and, additionally, present in cases of pleasure. Historically, morphine receptors were discovered in the nervous system before the discovery and understanding of endorphins. This natural receptor spoke to the possibility of the existence and effect of endorphins that was later confirmed.
Endorphins were discovered to not only display functions as neurotransmitters in the central nervous system but additionally as peptide hormones released into the circulatory system by the pituitary gland. Endorphins have been linked clinically to cases of mental issues including autism, depression, and depersonalization disorder as well as to activities such as laughter and vigorous aerobic exercise.