Select the correct statement.

Correct Answer: D

Rationale: The correct answer is D because insulin is released by β cells in the pancreas and its main function is to lower blood sugar levels by promoting the uptake of glucose into cells. β cells are located in the Islets of Langerhans in the pancreas and are responsible for producing and releasing insulin in response to high blood sugar levels. A, B, and C are incorrect: A: Insulin is not released by α cells; glucagon is the hormone released by α cells that increases blood sugar levels. B: Insulin lowers blood sugar, so it is not released by α cells, and α cells do not lower blood sugar. C: Insulin is released by β cells, not α cells, and it decreases blood sugar levels, not increases them.

Correct Answer: A

Rationale: The correct answer is A: calcitonin and parathyroid hormone. Calcitonin decreases blood calcium levels, while parathyroid hormone increases blood calcium levels. They have opposing actions, thus producing antagonistic results. Summary: - FSH and LH (choice B) work together in the reproductive system. - ADH and vasopressin (choice C) are different names for the same hormone. - Oxytocin and prolactin (choice D) have complementary roles in milk production and breastfeeding.

Correct Answer: D

Rationale: The correct answer is D: cortisol. Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate sources, primarily in the liver. Cortisol plays a key role in stimulating gluconeogenesis by promoting the breakdown of proteins and fats to generate substrates for glucose production. Aldosterone, insulin, and secretin do not directly stimulate gluconeogenesis. Aldosterone regulates electrolyte balance, insulin promotes glucose uptake and storage, and secretin stimulates pancreatic enzyme secretion. Cortisol is the hormone responsible for activating gluconeogenesis in the liver.

Correct Answer: C

Rationale: The correct answer is C because the ability of a tissue or organ to respond to a hormone depends on the presence of specific receptors on the cells of the target tissue. These receptors are like locks that only fit the specific key (hormone). Without the appropriate receptors, the hormone cannot initiate a response. A: The location of the tissue or organ with respect to the circulatory path may affect the speed of hormone delivery but does not determine the tissue's ability to respond. B: The membrane potential of the cells of the target organ relates to cell signaling but does not determine the specificity of hormone response. D: This choice is incorrect because hormones are specific and can only bind to cells with the appropriate receptors, making the statement that all hormones can stimulate any cell type nonsensical.

Correct Answer: C

Rationale: Mineralocorticoids regulate electrolyte and fluid balance, with aldosterone being the primary mineralocorticoid. Glucocorticoids regulate metabolism and immune response, with cortisol being the primary glucocorticoid. Therefore, the correct answer is C: cortisol. Testosterone (A) and estrogen (B) are sex hormones, not corticosteroids. Epinephrine (D) is a hormone produced by the adrenal medulla, not a corticosteroid.