The answer is the endogenous opiate.
The human body naturally produces its own opiates like substances and uses them as neurotransmitters. These substances include endorphins, enkephalins, and dynorphin, often collectively known as endogenous opioids. Endogenous opioids modulate our reactions to painful stimuli.
The distinction between protostomes and deuterostomes is based on differences in their embryological development. Protostomes develop their oral end from their first developmental opening, while deuterostomes have their oral end develop from the second opening on the dorsal surface.
<span>cellular respiration
Hope it helps</span>
