Virtually all of the protein or amino acid-based hormones exert their effects through intracellular ________.

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: 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.

Correct Answer: A

Rationale: The correct answer is A: humoral. Humoral regulation refers to the control of physiological processes by substances in the blood, such as hormones. In this case, the production and release of hormones in response to a chemical like calcium is an example of humoral mechanism. This choice is correct because it specifically involves the blood-borne substances affecting hormone production. Choices B, C, and D are incorrect because neural regulation (B) involves the nervous system controlling physiological processes, sensory regulation (C) refers to sensory input influencing responses, and hormonal regulation (D) involves feedback loops within the endocrine system, not directly related to blood-borne substances like calcium.

Correct Answer: C

Rationale: The correct answer is C: diabetes insipidus. The inability to produce ADH (antidiuretic hormone) results in diabetes insipidus, characterized by excessive thirst and urination. ADH plays a crucial role in regulating water retention by the kidneys. Without ADH, the kidneys are unable to concentrate urine, leading to increased urine output and dehydration. A: Diabetes mellitus is not caused by the inability to produce ADH. It is a condition characterized by high blood sugar levels due to insufficient insulin production or ineffective use of insulin. B: Uterine contractions are not related to the production of ADH. Uterine contractions are primarily controlled by hormones such as oxytocin during labor. D: Decreased urine volume is the opposite of what occurs in diabetes insipidus. In this condition, there is an increase in urine volume due to the inability to concentrate urine.