The adrenal cortex:

Correct Answer: A

Rationale: Step-by-step rationale: 1. The adrenal cortex is the outer layer of the adrenal gland that produces steroid hormones. 2. ACTH (adrenocorticotropic hormone) stimulates the adrenal cortex to secrete cortisol and aldosterone. 3. Therefore, the adrenal cortex is the target gland of ACTH, making choice A correct. Summary: A. Correct - The adrenal cortex is the target gland of ACTH. B. Incorrect - The adrenal medulla secretes catecholamines (e.g., adrenaline, noradrenaline). C. Incorrect - The sympathetic nervous system is responsible for the fight-or-flight response, not the adrenal cortex. D. Incorrect - ADH (antidiuretic hormone) and oxytocin are produced by the hypothalamus and released by the posterior pituitary gland, not the adrenal cortex.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Hypocalcemic tetany is associated with low levels of calcium in the blood. 2. Parathyroid hormone (PTH) plays a crucial role in calcium regulation. 3. A deficiency of PTH can lead to decreased calcium levels, causing tetany. 4. Therefore, choice C is correct as hypocalcemic tetany may be caused by a deficiency of PTH. Summary: A: Incorrect. Hypocalcemic tetany leads to muscle spasms, not flaccid paralysis. B: Incorrect. Curare blockade affects neuromuscular transmission, not calcium levels. D: Incorrect. Insulin deficiency is associated with hyperglycemia, not hypocalcemia leading to tetany.

Correct Answer: C

Rationale: Rationale: 1. Myxedema is caused by hypothyroidism, which can be effectively treated with thyroxine. 2. Thyroxine is a synthetic form of thyroid hormone that helps restore thyroid hormone levels. 3. Myxedema symptoms such as fatigue, weight gain, and cold intolerance improve with thyroxine treatment. Summary of Incorrect Choices: A. Diabetes mellitus and hyperglycemia are not directly related to thyroid hormone levels. B. Hyperglycemia is not primarily treated with thyroxine. D. Graves' disease is a thyroid disorder characterized by hyperthyroidism, which requires different treatments than hypothyroidism.

Correct Answer: D

Rationale: Step-by-step rationale: 1. Hypocalcemic tetany results from low blood calcium levels. 2. Parathyroid hormone (PTH) regulates calcium levels by increasing calcium release from bones and reabsorption in the kidneys. 3. A deficiency in parathyroid activity leads to decreased calcium levels, causing tetany. 4. Choice D is correct as it directly links hypocalcemic tetany to parathyroid dysfunction. Summary: A: Incorrect, calcitonin lowers blood calcium levels. B: Incorrect, TSH regulates thyroid function, not calcium levels. C: Incorrect, osteoclasts break down bone tissue but are not directly related to hypocalcemic tetany.

Correct Answer: A

Rationale: The correct answer is A: Adrenal medulla. The adrenal medulla secretes adrenaline and noradrenaline, which are hormones that enhance the sympathetic response of the body. This response includes increased heart rate, dilation of airways, and increased blood flow to muscles. The other choices, B: Pancreas, C: Adrenal cortex, and D: Parathyroid, do not directly enhance sympathetic responses. The pancreas regulates blood sugar levels, the adrenal cortex produces cortisol and aldosterone, and the parathyroid regulates calcium levels. Therefore, only the adrenal medulla directly contributes to the sympathetic response, making it the correct choice.