Tropic hormones:

Correct Answer: C

Rationale: The correct answer is C: Tropic hormones stimulate other endocrine glands to secrete hormones. Tropic hormones are released from the anterior pituitary gland and act on target glands to regulate the secretion of specific hormones. They help maintain homeostasis by controlling hormone levels in the body. Choices A and B are incorrect because tropic hormones do not target the pineal gland or thymus gland. Choice D is incorrect because tropic hormones primarily target endocrine glands, not nervous tissue. In summary, tropic hormones play a key role in regulating hormone production in other endocrine glands, making choice C the correct answer.

Correct Answer: D

Rationale: The correct answer is D: second messengers. Protein or amino acid-based hormones are unable to pass through the cell membrane due to their large size and hydrophilic nature. Therefore, they bind to specific receptors on the cell surface, triggering a series of events that lead to the production of second messengers inside the cell. These second messengers, such as cyclic AMP or calcium ions, then transmit the hormonal signal to the target cell's interior to initiate a physiological response. Choices A, B, and C are incorrect because protein or amino acid-based hormones do not directly exert their effects through ions, deactivators, or nucleotides intracellularly.

Correct Answer: D

Rationale: The correct answer is D because the neurohypophysis stores hormones produced by the hypothalamus for release into the bloodstream. The neurohypophysis does not produce its own hormones but acts as a storage and release site. A is incorrect as the neurohypophysis does play a role in hormonal release through the release of hormones produced by the hypothalamus. B is incorrect as the neurohypophysis remains functional in adults. C is incorrect as the neurohypophysis does function as an endocrine tissue by releasing hormones into the bloodstream.

Correct Answer: B

Rationale: The correct answer is B: aldosterone. Aldosterone is a hormone produced by the adrenal glands that plays a key role in regulating electrolyte concentrations in extracellular fluids. It specifically acts on the kidneys to increase the reabsorption of sodium and water while promoting the excretion of potassium. This helps to maintain the balance of electrolytes in the body. Insulin, glucagon, and cortisol do not directly regulate electrolyte concentrations in extracellular fluids. Insulin regulates blood sugar levels, glucagon regulates glucose release from the liver, and cortisol is involved in stress response and metabolism. Therefore, aldosterone is the most important regulator of electrolyte concentrations in extracellular fluids.

Correct Answer: C

Rationale: Step 1: Follicle-stimulating hormone (FSH) is essential for sperm production in males. Step 2: FSH is produced in the anterior pituitary gland. Step 3: In males, FSH stimulates the Sertoli cells in the testes to support sperm production. Step 4: Therefore, if a man is not synthesizing enough FSH, it can lead to reduced sperm production and fertility issues. Summary: A: Incorrect - FSH is synthesized by males in the anterior pituitary gland, not just females for estrogen secretion. B: Incorrect - Hormones produced in the adenohypophysis, like FSH, play a crucial role in fertility. D: Incorrect - Progesterone does not inhibit the synthesis of FSH; it is involved in the female reproductive system, not male fertility.