Which hormone is responsible for the reabsorption of sodium in the kidneys?

Correct Answer: A

Rationale: Aldosterone is the correct answer because it specifically acts on the kidneys to increase the reabsorption of sodium. It is produced by the adrenal glands in response to low blood pressure or low sodium levels. Aldosterone binds to receptors in the kidneys, leading to increased sodium reabsorption and potassium excretion. Angiotensin plays a role in stimulating the release of aldosterone, but it does not directly affect sodium reabsorption. ADH regulates water reabsorption, not sodium. ACTH stimulates the adrenal glands to produce cortisol, not aldosterone. Therefore, aldosterone is the hormone responsible for the reabsorption of sodium in the kidneys.

Correct Answer: B

Rationale: The correct answer is B: controls the amount of urine one produces. Antidiuretic hormone (ADH) acts on the kidneys to regulate water reabsorption, thereby controlling the amount of urine produced. It does not control metabolic rate (A), increase blood sugar (C), or control reproduction (D). ADH's main function is to maintain water balance in the body by reducing urine output.

Correct Answer: B

Rationale: The correct answer is B: Thyroid. The body's major metabolic hormone, thyroxine (T4) and triiodothyronine (T3), is released from the thyroid gland. The thyroid gland plays a crucial role in regulating metabolism. Pituitary (A) releases various hormones but not the major metabolic hormone. Thymus (C) is responsible for immune function, not metabolism. Hypothalamus (D) regulates the pituitary gland but does not directly release the major metabolic hormone.

Correct Answer: C

Rationale: The correct answer is C: anterior pituitary. Hypothalamic releasing hormones target cells in the anterior pituitary to stimulate the release of specific pituitary hormones. The hypothalamus produces releasing hormones that travel through the hypophyseal portal system and bind to receptors on cells in the anterior pituitary, triggering the release of hormones such as ACTH, TSH, LH, FSH, and GH. This interaction between the hypothalamus and anterior pituitary forms the hypothalamic-pituitary axis, regulating various physiological processes. Choices A (thyroid) and D (posterior pituitary) are incorrect as they are not the primary targets of hypothalamic releasing hormones. Choice B (hypothalamus) is also incorrect as releasing hormones do not target cells within the hypothalamus itself, but rather the anterior pituitary.

Correct Answer: A

Rationale: The correct answer is A: enzyme. Endocrine glands are stimulated by three main categories: humoral (based on blood levels of certain substances), neural (stimulation by nerves), and hormonal (stimulation by other hormones). Enzymes do not directly stimulate endocrine glands. They are biological catalysts that facilitate biochemical reactions, not a category of stimulus for endocrine glands. Therefore, A is the correct answer. Choices B, C, and D are incorrect as they are valid categories of endocrine gland stimulus based on blood levels, nerves, and hormones respectively.