This Hormone Is Responsible for the 'Fight-or-Flight' Response

Correct Answer: C

Rationale: The correct answer is C: Epinephrine and norepinephrine. These hormones are responsible for the 'fight-or-flight' response. When the body perceives a threat, these hormones are released by the adrenal glands, preparing the body for a rapid response to danger. Epinephrine increases heart rate, blood pressure, and blood flow to muscles, while norepinephrine helps maintain alertness and focus. Choice A (Thyroxine and melatonin) are hormones involved in regulating metabolism and sleep-wake cycles, not the 'fight-or-flight' response. Choice B (Insulin and glucagon) are hormones that regulate blood sugar levels, not the 'fight-or-flight' response. Choice D (Oestrogen and progesterone) are reproductive hormones that regulate the menstrual cycle and pregnancy, not the 'fight-or-flight' response.

Correct Answer: D

Rationale: The liberation of proteins to free amino acids occurs primarily in the small intestine lumen. In the stomach, proteins are broken down into smaller peptides but not fully liberated to amino acids. The enterocyte cytoplasm is where amino acids are absorbed. The brush border aids in absorption but doesn't release proteins to amino acids. Therefore, the correct answer is D (stomach) as it is not the site for the final step of protein digestion.

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.