Which statement about the reaction is correct?

Correct Answer: A

Rationale: The correct answer is A because an endothermic reaction absorbs thermal energy from the surroundings to proceed. In an endothermic reaction, the products have higher potential energy than the reactants, requiring energy input. Choice B is incorrect as endothermic reactions do not transfer thermal energy to the surroundings. Choices C and D are incorrect as they describe exothermic reactions, where thermal energy is released to the surroundings.

Correct Answer: B

Rationale: The correct answer is B: iodine. Iodine is an essential element required for the synthesis of thyroid hormone. Thyroid hormones such as thyroxine (T4) and triiodothyronine (T3) contain iodine atoms. Without sufficient iodine, the thyroid gland cannot produce these hormones, leading to thyroid disorders like hypothyroidism or goiter. Copper (A), sulfur (C), and zinc (D) are not directly involved in the synthesis of thyroid hormone. Copper is important for enzyme function, sulfur is present in amino acids, and zinc is involved in various cellular processes but not specifically in thyroid hormone synthesis.

Correct Answer: A

Rationale: The correct answer is A: damage to the pineal gland. The pineal gland does not regulate ADH secretion; it primarily produces melatonin. Neurosurgery and general anesthesia may disrupt the feedback mechanisms controlling ADH release. Ectopic ADH secretion by pulmonary cancer can lead to excessive ADH production. The key is to identify a situation where ADH hypersecretion is less likely to occur due to the gland's function.

Correct Answer: C

Rationale: The middle thyroid vein drains into the internal jugular vein due to its anatomical location in the neck. The internal jugular vein receives blood from the brain, face, and neck, making it a suitable drainage site for the thyroid gland. The other options (A, B, D) are incorrect because the brachiocephalic vein drains the upper body, the external jugular vein drains the scalp and face, and the subclavian vein drains the upper extremities, none of which are anatomically linked to the thyroid gland.

Correct Answer: c

Rationale: The correct answer is D: Parathyroid. The parathyroid gland secretes parathyroid hormone (PTH) when blood calcium levels are elevated. PTH acts to increase calcium reabsorption in the kidneys, release calcium from bones, and enhance calcium absorption in the intestines, ultimately lowering blood calcium levels back to normal. A: The hypothalamus plays a role in regulating body temperature, thirst, hunger, and circadian rhythms, but not in calcium homeostasis. B: The pituitary gland secretes various hormones, but none specifically involved in regulating blood calcium levels. C: The thyroid gland secretes thyroid hormones that regulate metabolism and growth, not calcium levels.