The antagonistic hormone to calcitonin is _____.

Correct Answer: D

Rationale: The correct answer is D: parathyroid hormone. Calcitonin and parathyroid hormone regulate calcium levels in the blood. Calcitonin lowers blood calcium levels by inhibiting bone resorption, while parathyroid hormone increases blood calcium levels by promoting bone resorption. Thus, they have opposite effects on calcium regulation, making parathyroid hormone the antagonistic hormone to calcitonin. Thyroxine (A), growth hormone (B), and insulin (C) do not directly oppose the action of calcitonin in regulating calcium levels.

Correct Answer: D

Rationale: The correct answer is D: Increases blood calcium level. Parathormone is released by the parathyroid glands in response to low blood calcium levels. It acts to increase blood calcium levels by stimulating the release of calcium from bones, increasing calcium absorption in the intestines, and promoting calcium reabsorption in the kidneys. This helps to maintain proper calcium levels in the body. Choices A, B, and C are incorrect because parathormone does not have any direct effect on blood sodium levels and actually works to increase, not decrease, blood calcium levels.

Correct Answer: D

Rationale: The correct answer is D - Melatonin - Regulates the rate of cellular metabolism. Melatonin is a hormone primarily involved in regulating sleep-wake cycles, not cellular metabolism. A: Calcitonin - Lower blood calcium levels - Correct. Calcitonin is released by the thyroid gland to lower blood calcium levels. B: Parathyroid - Raises blood calcium levels - Correct. Parathyroid hormone is released by the parathyroid glands to raise blood calcium levels. C: Somatostatin - Inhibits release of glucagon - Correct. Somatostatin inhibits the release of glucagon and insulin.

Correct Answer: A

Rationale: The correct answer is A: Oestrogen. Ovaries secrete oestrogen, a key female sex hormone involved in the development of secondary sexual characteristics, regulation of the menstrual cycle, and maintenance of pregnancy. Luteinising hormone (B) and follicle stimulating hormone (C) are secreted by the pituitary gland to regulate ovarian function. Oxytocin (D) is produced by the hypothalamus and released by the pituitary gland for uterine contractions and milk ejection, not by the ovaries. Therefore, A is correct as ovaries primarily produce oestrogen.

Correct Answer: B

Rationale: The correct answer is B: vagus. The efferent swallow reflex involves motor nerves responsible for swallowing. The vagus nerve is primarily responsible for the afferent (sensory) pathway in the swallow reflex, while the efferent pathway involves the trigeminal, facial, and hypoglossal nerves. The trigeminal nerve (A) controls chewing muscles, the facial nerve (C) is responsible for facial expressions and some swallowing muscles, and the hypoglossal nerve (D) controls the movement of the tongue during swallowing. Therefore, the vagus nerve is not directly involved in the efferent motor control of swallowing, making it the correct answer.