A 38-year-old man with galactorrhea is treated with bromocriptine, which eliminates the galactorrhea. The basis for the therapeutic action of bromocriptine is that it

Correct Answer: C

Rationale: Step-by-step rationale: 1. Bromocriptine is a dopamine agonist. 2. Dopamine inhibits prolactin release from the anterior pituitary. 3. Galactorrhea is often caused by excess prolactin. 4. By inhibiting prolactin release, bromocriptine reduces prolactin levels and eliminates galactorrhea. Summary: A: Incorrect - Bromocriptine does not antagonize prolactin action. B: Incorrect - Bromocriptine does not enhance prolactin action. D: Incorrect - Prolactin is not released from the hypothalamus.

Correct Answer: B

Rationale: The correct answer is B: steroid hormones, because both diffuse easily into target cells. Thyroid hormone, being a small iodinated amine, can easily pass through the cell membrane and bind to intracellular receptors, similar to steroid hormones. Unlike insulin (choice A), which binds to cell surface receptors, thyroid hormone and steroid hormones enter the cell to exert their effects. Growth hormone (choice C) and glucagon (choice D) do not share the same mechanism of entry into target cells as thyroid hormone, making them incorrect choices.

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.