The antagonistic hormone to insulin is __________.

Correct Answer: C

Rationale: The correct answer is C: glucagon. Glucagon is the hormone that opposes the actions of insulin by increasing blood glucose levels. When blood sugar levels are low, glucagon signals the liver to release stored glucose, raising blood sugar levels. Cortisol (A) and mineralocorticoids (D) are not directly antagonistic to insulin. Norepinephrine/epinephrine (B) play a role in the fight-or-flight response, but they do not directly counteract insulin's actions on glucose regulation.

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.

Correct Answer: A

Rationale: The correct answer is A because gastrin primarily stimulates gastric acid secretion and gastric mucosal growth but not insulin secretion. Gastrin acts on parietal cells to stimulate acid production and chief cells to release pepsinogen. Choice B and C are incorrect as gastrin does have a trophic effect on colonic and gastric mucosa, respectively. Choice D is also incorrect as gastrin stimulates pepsin secretion.