Final answer:
The incorrect statement about cholecystokinin (CCK) is that it acts directly on neurons of the ventromedial hypothalamus. CCK has various roles in digestion and appetite suppression, but its action is not direct on those neurons.
Step-by-step explanation:
The statement about cholecystokinin (CCK) that is not true is: "The site of action for CCK is directly on neurons of the ventromedial hypothalamus."
CCK is a gastrointestinal hormone that plays a crucial role in digestive processes. Primarily, it stimulates the release of pancreatic enzymes and the contraction of the gallbladder to release bile salts, crucial for lipid digestion. Its blood levels rise after a meal high in fats, indicating its role in fat digestion. CCK also has effects on gastric motility by inhibiting gastric contractions, thus slowing down the gastric emptying. Moreover, CCK has an indirect effect on appetite suppression through its action on the brain, but it does not act directly on the neurons of the ventromedial hypothalamus; rather, it influences hunger cues by interacting with other pathways.