Which of the following cranial nerves carries sensation from the digestive tract to the CNS?

Correct Answer: B

Rationale: The correct answer is B: vagus. The vagus nerve, or cranial nerve X, carries sensation from the digestive tract to the CNS. It is a major player in the parasympathetic nervous system, controlling many vital functions including digestion. The other options, gastric and spinal accessory, are not cranial nerves responsible for carrying sensations from the digestive tract. Choice D is incorrect as the vagus nerve specifically serves this function.

Correct Answer: C

Rationale: The correct answer is C: protein. Gastric secretions primarily consist of hydrochloric acid and pepsin, which break down proteins into smaller peptides. This process is essential for protein digestion in the stomach. Choices A, B, and D are incorrect because fats are primarily digested in the small intestine with the help of bile, starch is broken down by amylase in the mouth and small intestine, and nucleic acids are digested in the small intestine by nucleases. Therefore, protein is the major food digested by gastric secretions due to the presence of pepsin and hydrochloric acid in the stomach.

Correct Answer: B

Rationale: The correct answer is B: ileum. The ileum is the longest region of the small intestine, measuring about 6-7 meters in length. It is responsible for further digestion and absorption of nutrients, particularly vitamin B12 and bile salts. The duodenum is the first part of the small intestine and is relatively short, the jejunum is the middle section of the small intestine, and the colon is part of the large intestine. Therefore, the ileum is the correct answer based on its length and function in the digestive process.

Correct Answer: D

Rationale: The correct answer is D, cholecystokinin. Cholecystokinin is released in response to the presence of fatty acids and amino acids in the duodenum, stimulating the secretion of the enzymatic component of pancreatic juice. Gastric inhibitory polypeptide (A) regulates insulin release, not pancreatic enzyme secretion. Secretin (B) stimulates bicarbonate secretion from the pancreas, not enzyme secretion. Gastrin (C) stimulates gastric acid secretion, not pancreatic enzyme secretion. Therefore, cholecystokinin is the correct hormone for stimulating the enzymatic component of pancreatic juice secretion.

Correct Answer: A

Rationale: The correct answer is A: stomach and pancreas. Firstly, protein digestion starts in the stomach where pepsinogen is converted to pepsin, breaking down proteins. Secondly, the pancreas secretes enzymes like trypsin and chymotrypsin into the small intestine to further break down proteins. The other choices are incorrect because the salivary glands primarily produce enzymes for carbohydrate digestion, while the small intestine is more involved in absorbing nutrients rather than producing protein-digesting enzymes.