Stimulation by the sympathetic nervous system will cause which one of the following effects in the inferior esophagus, stomach, small intestine and large intestine?

Correct Answer: C

Rationale: The correct answer is C: decreases peristalsis by inhibition of smooth muscle. The sympathetic nervous system inhibits gastrointestinal motility by decreasing peristalsis. This is achieved through the release of norepinephrine, which binds to adrenergic receptors on smooth muscle cells, leading to reduced contraction and motility. Choices A and B are incorrect because the sympathetic nervous system can still affect smooth muscle, not just skeletal muscle. Choice D is incorrect because sympathetic stimulation does not directly increase peristalsis.

Correct Answer: D

Rationale: The correct answer is D. Salivary secretion is stimulated by the salivary nucleus in the brainstem and local reflexes in the tunica mucosa and submucosa of the oral cavity. The salivary nucleus receives input from higher brain centers and initiates the salivary reflex. Local reflexes in the oral cavity, such as mechanical stimulation of the mucosa, also trigger salivary secretion. Gastrin, as mentioned in option B and C, is not directly involved in the stimulation of salivary secretion. Option A is incorrect as salivary secretion is not solely stimulated by the salivary nucleus. Option D encompasses the comprehensive stimulation pathways involved in salivary secretion.

Correct Answer: A

Rationale: Parasympathetic stimulation triggers the release of gastrin from endocrine cells in the stomach. Gastrin plays a key role in promoting gastric acid secretion and stimulating gastric motility. This hormone is essential for regulating digestion. Incorrect choices: B: Pepsinogen is an inactive form of pepsin, which is not released by endocrine cells in the stomach. C: Histamine is released by mast cells and enterochromaffin-like cells, not endocrine cells in the stomach. D: Secretin is released by the S cells in the duodenum in response to low pH in the small intestine, not by endocrine cells in the stomach.

Correct Answer: B

Rationale: The correct answer is B because bile salts emulsify fat into smaller droplets, increasing the surface area for enzymes to break down fats into fatty acids and glycerol. This aids in fat digestion and absorption in the small intestine. Choice A is incorrect as bile salts do not directly break down fats into fatty acids and glycerol. Choice C is incorrect as bile salts do not break down fats into cholesterol and lecithin. Choice D is incorrect as bile salts do not emulsify fats to bilirubin, but rather help in the digestion of fats.

Correct Answer: D

Rationale: The correct answer is D: bacteria. Enzymes in the large intestine are primarily produced by the gut microbiota, which are bacteria residing in the colon. These bacteria play a crucial role in the breakdown of complex carbohydrates and the production of certain vitamins, including Vitamin K. Goblet cells (A) produce mucus, simple columnar cells (B) are involved in absorption, and teniae coli (C) are muscle bands in the colon - none of which are directly responsible for enzyme production or Vitamin K synthesis in the large intestine.