Final answer:
The naturally occurring opioid peptides in the body are endorphins, enkephalins, and dynorphins; they are part of the endogenous opioid system that reduce pain and induce euphoria.
Step-by-step explanation:
The naturally occurring opioid peptides in the body are endorphins, enkephalins, and dynorphins. These are small peptides with potent physiological activities, including reducing pain and producing euphoria.
They are part of the body's endogenous opioid neurotransmitter system which functions by binding to opioid receptors. This system is what opioid drugs, including painkillers and narcotics, seek to mimic when they are used medically or abused recreationally.
It is important to differentiate between these naturally occurring peptides and opioid drugs derived from the opium poppy or their synthetic versions, such as heroin, codeine, morphine, or OxyContin. These substances are external to the body and can have very potent painkilling effects, but they also hold a high potential for abuse.