As plasma levels of calcium decrease:

Correct Answer: B

Rationale: The correct answer is B because as plasma levels of calcium decrease, the parathyroid glands secrete an osteoclastic hormone called parathyroid hormone (PTH). PTH acts to increase calcium levels by stimulating the release of calcium from bones via osteoclasts. Insulin secretion (choice A) is not directly related to calcium levels. The kidneys excreting calcium and phosphorus (choice C) would further decrease calcium levels. Calcitonin (choice D) actually decreases blood calcium levels by inhibiting bone breakdown, so it is not secreted when calcium levels decrease.

Correct Answer: C

Rationale: Rationale: Myxedema, Graves' disease, and cretinism are all disorders directly related to the thyroid gland, involving either hypo or hyperactivity. Myxedema and cretinism are hypothyroid disorders, while Graves' disease is a hyperthyroid disorder. Thus, the correct answer is C. Choice A is incorrect as Graves' disease is a hyperthyroid disorder. Choice B is incorrect as these disorders are not solely due to a deficiency of TSH. Choice D is incorrect as treatment can vary depending on the specific disorder and may not always involve T3 and/or T4.

Correct Answer: C

Rationale: The correct answer is C (Pancreas, parathyroid, anterior pituitary) because glucagon is secreted by the pancreas, PTH (parathyroid hormone) is secreted by the parathyroid glands, and TSH (thyroid-stimulating hormone) is secreted by the anterior pituitary gland. Choice A (Neurohypophysis, pancreas, ovary) is incorrect because the neurohypophysis secretes oxytocin and ADH, not glucagon, PTH, or TSH. The ovary does not secrete any of these hormones. Choice B (Adrenal cortex, pancreas, neurohypophysis) is incorrect because the adrenal cortex secretes cortisol and aldosterone, not glucagon, PTH, or TSH. The neurohypophysis secretes oxytocin and ADH, not the hormones in question. Choice D (Testes, thymus, adenohypophysis

Correct Answer: C

Rationale: The correct answer is C: Pancreas. The pancreas is both an endocrine and exocrine gland. It secretes hormones like insulin and glucagon (endocrine function) into the bloodstream to regulate blood sugar levels, while also producing digestive enzymes (exocrine function) that are released into the small intestine to aid in digestion. The other choices are incorrect because: A: Thyroid - primarily an endocrine gland that produces hormones like thyroxine. B: Thymus - strictly an endocrine gland responsible for T-cell development. D: Pituitary - also an endocrine gland that controls various other endocrine glands in the body.

Correct Answer: B

Rationale: The correct answer is B: nervous system. The endocrine system and nervous system work together in maintaining the body's equilibrium through communication and regulation of bodily functions. The nervous system controls rapid responses, while the endocrine system regulates slower, long-term responses through hormones. The digestive system (A) primarily focuses on breaking down food and absorbing nutrients. The respiratory system (C) is responsible for gas exchange. The reproductive system (D) is involved in reproduction and hormone production, but not in maintaining the body's equilibrium.