**Question:** Effect of CCK on gut is

A. Inhibition of gastric secretion
B. Inhibition of pancreatic secretion
C. Increase in motility
D. Increase in bile secretion

**Core Concept:**

Cholecystokinin (CCK) is a gastrointestinal hormone produced primarily by Ileal enteroendocrine cells and cholecystokinin neurons in the brain. It plays a crucial role in the regulation of various gastrointestinal functions, including digestion, absorption, and secretory processes.

**Why the Correct Answer is Right:**

CCK has a significant effect on the gastrointestinal tract, particularly on the stomach, pancreas, and gallbladder. When it comes to the gut, CCK primarily acts on the following:

1. Inhibition of gastric secretion: CCK inhibits gastric secretion of gastric acid and pepsin, which reduces the risk of gastrointestinal ulcers and gastritis.
2. Inhibition of pancreatic secretion: CCK also inhibits pancreatic secretion of digestive enzymes, which helps prevent excessive digestion and ensures proper coordination between the stomach, small intestine, and pancreas.
3. Increase in motility: CCK stimulates the smooth muscles of the gastrointestinal tract, enhancing the peristalsis and facilitating the movement of food through the digestive system.
4. Increase in bile secretion: CCK stimulates the gallbladder to release bile into the small intestine, which aids in the digestion of fats.

**Why Each Wrong Option is Incorrect:**

A. CCK does inhibit gastric secretion, but the primary action is not inhibition of gastric secretion.
B. CCK inhibits pancreatic secretion, but its primary action is not on pancreatic secretion but on the coordination of the gastrointestinal system.
C. CCK does stimulate gut motility, but the primary action is not solely on motility.
D. CCK does increase bile secretion, but the primary action is not solely on bile secretion.

**Clinical Pearl:**

Understanding the complex actions of CCK on the gastrointestinal system is crucial in clinical practice, as it helps us comprehend the interconnected roles of different gastrointestinal organs and their coordinated functions. Proper knowledge of CCK effects can aid in diagnosing and treating gastrointestinal disorders such as gastritis, pancreatitis, and biliary tract diseases.