What Does Somatostatin Do?

Correct Answer: A

Rationale: The correct answer is A because somatostatin inhibits the release of both insulin and glucagon. This hormone acts as a regulator of the endocrine system by suppressing the secretion of these hormones. By inhibiting the release of insulin, somatostatin helps to prevent hypoglycemia, while inhibiting glucagon release helps to maintain blood glucose levels. Choices B, C, and D are incorrect because they do not accurately reflect the function of somatostatin in regulating the release of insulin and glucagon. B stimulates the release of both hormones, C stimulates glucagon while inhibits insulin, and D inhibits glucagon while stimulates insulin, which are all contradictory to the known actions of somatostatin.

Correct Answer: D

Rationale: Correct Answer: D Rationale: 1. Hemolytic anemia results in increased breakdown of red blood cells. 2. Bilirubin is produced during the breakdown of heme in red blood cells. 3. Increased breakdown leads to elevated unconjugated (indirect) bilirubin levels. 4. This unconjugated bilirubin can overwhelm the liver's conjugation capacity, causing hyperbilirubinemia. Summary: A: Incorrect. Conjugated bilirubin is more soluble than unconjugated. B: Incorrect. Conjugated bilirubin is excreted via urine, not intestine. C: Incorrect. Bile duct obstruction causes conjugated hyperbilirubinemia, not unconjugated.

Correct Answer: B

Rationale: The correct answer is B: vagus. The efferent (motor) swallow reflex involves motor nerves that control swallowing muscles. The vagus nerve (cranial nerve X) is primarily responsible for the afferent (sensory) component of the swallow reflex, while the efferent component is carried out by other cranial nerves such as the glossopharyngeal (IX), facial (VII), and hypoglossal (XII) nerves. Therefore, the vagus nerve is not directly involved in the efferent motor response during swallowing. Trigeminal (V), facial (VII), and hypoglossal (XII) nerves play essential roles in the motor aspects of swallowing, making them incorrect choices.

Correct Answer: C

Rationale: Rationale for Correct Answer (C): 1,25(OH)2 D3 and PTH stimulate both osteoblasts and osteoclasts. 1,25(OH)2 D3 enhances calcium absorption in the gut, promotes bone resorption, and stimulates osteoclast activity. PTH increases calcium levels in the blood by enhancing calcium reabsorption in the kidney and stimulating osteoclast activity. Both hormones indirectly stimulate osteoblasts by increasing calcium availability for bone formation. Summary of Incorrect Choices: A: Osteoclasts actually secrete acid, not alkaline phosphatase. B: Osteoblasts are derived from mesenchymal stem cells, not monocytes. D: Estrogens have a dual effect, inhibiting bone resorption by osteoclasts and stimulating bone formation by osteoblasts; their main effect is inhibiting osteoclast activity, not solely stimulating osteoblasts.

Correct Answer: C

Rationale: The correct answer is C because 1,25-dihydroxycholecalciferol, the active form of vitamin D, does induce calcium binding protein synthesis in mucosal cells, facilitating calcium absorption. This process occurs in the small intestine. Choices A and B are incorrect because around 30% of calcium is typically absorbed, and active transport of Ca2+ primarily occurs in the upper small intestine. Choice D is incorrect because phosphate does not directly facilitate calcium absorption.