Which gland is often referred to as the 'master gland'?

Correct Answer: A

Rationale: The pituitary gland is often referred to as the 'master gland' because it plays a crucial role in regulating other endocrine glands in the body. It secretes hormones that control various bodily functions, such as growth, reproduction, and metabolism. The other choices, thyroid, thymus, and hypothalamus, are important glands as well, but they do not have the same broad control over the endocrine system as the pituitary gland. The thyroid regulates metabolism, thymus is involved in immune function, and hypothalamus regulates body temperature, hunger, and thirst. However, none of these glands have the overall regulatory function and influence on other glands as the pituitary gland does.

Correct Answer: D

Rationale: The correct answer is D: Aldosterone. Aldosterone directly influences the reabsorption of sodium in the kidney tubules, leading to increased Na+ excretion. Progesterone (A) does not have a significant effect on Na+ excretion. Cortisol (B) mainly affects glucose metabolism and has minimal impact on Na+ excretion. Vasopressin (C) primarily regulates water reabsorption, not Na+ excretion. Therefore, Aldosterone has the greatest effect on Na+ excretion due to its specific role in sodium reabsorption in the kidneys.

Correct Answer: A

Rationale: Vitamin D is the correct answer as it is a steroid hormone synthesized from cholesterol. Steroid hormones are derived from cholesterol and have a similar chemical structure. Epinephrine and Insulin are not steroid hormones. Epinephrine is a catecholamine produced by the adrenal glands, and Insulin is a peptide hormone produced by the pancreas. Choice D is incorrect as not all options listed are steroid hormones.

Correct Answer: A

Rationale: The correct answer is A: negative feedback mechanisms. Negative feedback mechanisms are essential in regulating hormone levels within a narrow range to maintain homeostasis. When hormone levels rise, negative feedback mechanisms signal the body to decrease production, and vice versa. Positive feedback mechanisms amplify hormone production, not regulate it. Hormone-receptor complexes and hormone-gene complexes are important for hormone actions but do not regulate the overall endocrine system.

Correct Answer: A

Rationale: Step-by-step rationale: 1. The posterior pituitary gland stores oxytocin and antidiuretic hormone (ADH). 2. Oxytocin is responsible for uterine contractions and milk ejection. 3. ADH regulates water balance by controlling urine concentration. 4. These hormones are produced in the hypothalamus and released from the posterior pituitary. 5. Choice A is correct as it accurately identifies the hormones stored and secreted by the posterior pituitary. Summary: - Choice B is incorrect because human growth hormone and thyroid stimulating hormone are not stored or secreted by the posterior pituitary. - Choice C is incorrect because prolactin and follicle stimulating hormone are produced by the anterior pituitary. - Choice D is incorrect because glucocorticoids and androgens are not stored or secreted by the posterior pituitary.