Which of the Following Hormones Regulate Blood Sodium and Potassium Levels in the Body?

Correct Answer: A

Rationale: Aldosterone is the correct answer as it specifically regulates blood sodium and potassium levels by acting on the kidneys to enhance sodium reabsorption and potassium excretion. Cortisol is a stress hormone, not directly involved in electrolyte regulation. Glycogens are stored glucose molecules, not hormones. Pheromones are chemical signals for communication, not involved in electrolyte balance.

Correct Answer: D

Rationale: The correct answer is D, submandibular glands, as they produce the majority of salivary volume. These glands are the largest of the major salivary glands and secrete saliva rich in enzymes and mucin, contributing significantly to the total saliva volume. The lingual glands (A) are minor salivary glands located in the tongue and contribute a small portion of saliva. The sublingual glands (B) are also minor salivary glands located beneath the tongue, producing a smaller volume compared to the submandibular glands. The parotid glands (C) are another major salivary gland, but they produce a lesser volume of saliva compared to the submandibular glands.

Correct Answer: C

Rationale: Rationale: Gastrin secretion is primarily stimulated by luminal peptides and vagal discharge, which promote gastric acid secretion. Luminal acid, on the other hand, inhibits gastrin release as it acts as a negative feedback mechanism to regulate acid production. Phenylalanine does not directly stimulate gastrin secretion. Therefore, the correct answer is C as luminal acid inhibits, not stimulates, gastrin release. The other choices are incorrect because luminal peptides and vagal discharge are known stimulants of gastrin secretion, while phenylalanine does not have a direct effect on gastrin release.

Correct Answer: A

Rationale: The correct answer is A because gastrin primarily stimulates gastric acid secretion and gastric motility, not insulin secretion. Gastrin is released in response to the presence of food in the stomach, leading to increased gastric acid production and motility to aid in digestion. Insulin secretion is mainly regulated by glucose levels in the blood and hormones like insulin and glucagon. Therefore, the stimulation of insulin secretion after a carbohydrate meal is not a direct action of gastrin. Choices B, C, and D are incorrect because they accurately describe the actions of gastrin in the digestive system.

Correct Answer: A

Rationale: Step 1: NAD+ is a reactant in the citric acid cycle, not a product. Step 2: NAD+ is reduced to NADH during the cycle. Step 3: NAD+ is not directly produced as a final product in the cycle. Step 4: Therefore, A: NAD+ is NOT produced by the citric acid cycle. Summary: B: CO2 and D: FADH2 are produced in the cycle, while C: GTP is generated through substrate-level phosphorylation.