Identify a common function of atrial natriuretic hormone (ANH), aldosterone and antidiuretic hormone.Which of the following hormones does NOT help regulate blood pressure and volume?

Correct Answer: C

Rationale: The correct answer is C: oxytocin. Atrial natriuretic hormone (ANH), aldosterone, and antidiuretic hormone (ADH) all play a role in regulating blood pressure and volume. ANH promotes sodium and water excretion, aldosterone increases sodium reabsorption, and ADH controls water reabsorption. On the other hand, oxytocin is a hormone involved in uterine contractions during childbirth and milk ejection during breastfeeding, not directly related to blood pressure regulation. Therefore, oxytocin is the hormone that does NOT help regulate blood pressure and volume.

Correct Answer: A

Rationale: The correct answer is A: Aldosterone. The adrenal cortex is responsible for producing aldosterone, a hormone that regulates blood pressure and electrolyte balance. Aldosterone is specifically produced in the zona glomerulosa layer of the adrenal cortex. Adrenaline (Choice B) is produced by the adrenal medulla, not the cortex. Glucagon (Choice C) is produced by the pancreas, not the adrenal cortex. Calcitonin (Choice D) is produced by the thyroid gland, not the adrenal cortex. Therefore, the correct answer is A because aldosterone is the hormone produced by the adrenal cortex.

Correct Answer: C

Rationale: The correct answer is C: GIP (glucose-dependent insulinotropic peptide). GIP is an incretin hormone released from the small intestine in response to glucose ingestion, stimulating insulin secretion from pancreatic beta cells. Gastrin (A), CCK (B), and secretin (D) are gastrointestinal hormones that do not directly influence insulin secretion. GIP plays a crucial role in regulating blood sugar levels by promoting insulin release, making it the most important hormone in insulin secretion.

Correct Answer: A

Rationale: The correct answer is A because blood vessels in the gut are primarily innervated by sympathetic and parasympathetic fibers, not by enteric nerves. Enteric nerves are confined to the gastrointestinal tract itself and are responsible for regulating gut motility, secretion, and blood flow. Sympathetic innervation typically causes vasoconstriction, while parasympathetic innervation promotes vasodilation. The myenteric plexus (Auerbach's plexus) lies between the longitudinal and circular muscle layers, regulating gut motility. Parasympathetic supply to the gut is mainly through the vagus nerve (cranial nerve X) and sacral nerves (pelvic splanchnic nerves). Sympathetic supply can either be inhibitory or excitatory, but generally, sympathetic fibers are inhibitory on cholinergic postganglionic fibers in the gut.

Correct Answer: C

Rationale: The correct answer is C: theophylline. Theophylline stimulates insulin secretion by increasing cAMP levels in pancreatic beta cells, leading to enhanced insulin release. Thiazide diuretics (A) can actually reduce insulin secretion. Phenytoin (B) and beta blockers (D) are known to inhibit insulin secretion. Therefore, theophylline is the only choice that directly stimulates insulin secretion.