Oxytocin ________.

Correct Answer: A

Rationale: The correct answer is A because oxytocin release is an example of a positive feedback control mechanism. When oxytocin is released during childbirth, it stimulates contractions, which in turn lead to more oxytocin release, creating a positive feedback loop. This helps in the progression of labor. Choice B is incorrect because oxytocin is a neurohypophyseal hormone, not an adenohypophyseal secretion. Choice C is incorrect as oxytocin's main effects are related to labor, delivery, and lactation, not menstruation. Choice D is incorrect because oxytocin primarily controls uterine contractions during labor and milk ejection during breastfeeding, not milk production itself.

Correct Answer: D

Rationale: The correct answer is D because hormones from the hypothalamus first enter the hypophyseal portal system before reaching the pituitary gland. This system allows direct communication between the hypothalamus and the pituitary gland, enabling precise control over hormone release. Choices A, B, and C are incorrect because they do not accurately describe the normal pathway of hormone regulation from the hypothalamus to the pituitary gland. Option A is incorrect as hormones do not travel to the heart before reaching the pituitary. Option B is incorrect because hormones do not enter the hepatic portal system to reach the pituitary. Option C is incorrect as hormones do not travel to the pituitary through arteries.

Correct Answer: C

Rationale: The correct answer is C: nervous. The endocrine system and the nervous system work together to regulate various bodily functions and maintain homeostasis. The endocrine system releases hormones that control metabolism, growth, and reproduction, while the nervous system sends electrical signals to coordinate body movements and responses. Both systems communicate and coordinate with each other to ensure the body functions properly. Choices A, B, and D are incorrect because although they are important systems in the body, they do not play as direct a role in maintaining homeostasis as the nervous system does.

Correct Answer: D

Rationale: The correct answer is D because all the listed hormones are indeed produced by the hypothalamus. Oxytocin and antidiuretic hormone are directly synthesized in the hypothalamus and transported to the posterior pituitary for release. The hypothalamus also secretes releasing and inhibiting hormones that regulate the secretion of hormones from the anterior pituitary. Therefore, choices A, B, and C are incorrect on their own as they do not encompass all hormones produced by the hypothalamus.

Correct Answer: C

Rationale: The correct answer is C: acromegaly. In adults, overproduction of growth hormone leads to acromegaly, characterized by enlarged bones and tissues. Pituitary dwarfism (choice A) results from growth hormone deficiency. Gigantism (choice B) occurs when excess growth hormone is produced before epiphyseal plate closure in children. Myxedema (choice D) is associated with hypothyroidism, not growth hormone overproduction. Therefore, choice C is the correct answer as it specifically refers to the condition resulting from excessive growth hormone in adults.