Oxytocin and cholecystokinin are transported through the bloodstream and arrive at the uterus at the same time. Why does oxytocin cause the uterus to contract, whereas cholecystokinin has no effect?

Answer:The uterus has receptors for oxytocin, but not for cholecystokinin.

Explanation:

Both of the hormones are released and travel via same pathway towards the uterus. The uterus responds to oxytocin but does not responds to cholecystokinin because the uterus has no receptor for this hormone.

Cholesystokinin is secreted from gastrointestinal system and is responsible for stimulating the digestion of protein and fat.

Whereas oxytocin plays a major role in the childbirth, sexual reproduction and social bonding.