Which stimulates parietal cell secretion?

Correct Answer: D

Rationale: The correct answer is D: acetylcholine. Acetylcholine directly stimulates parietal cells in the stomach to secrete hydrochloric acid. It binds to muscarinic receptors on parietal cells, leading to an increase in acid production. Prostaglandins (A) inhibit acid secretion, aspirin (B) can cause gastric irritation and ulcers, and vinegar (C) does not directly stimulate parietal cells.

Correct Answer: B

Rationale: The correct answer is B because insulin deficiency leads to increased gluconeogenesis due to the lack of inhibition on glucose production. Choice A is incorrect as insulin binds to GLUT 4 receptors, not GLUT 1-5. Choice C is wrong because insulin's half-life is only a few minutes. Choice D is also inaccurate as insulin is secreted by pancreatic beta cells, not A cells.

Correct Answer: B

Rationale: Step-by-step rationale for the correct answer (B): 1. During starvation, the body shifts to using ketoacids derived from fats for fuel. 2. The brain and other tissues can utilize these ketoacids. 3. This process helps to spare protein and prevent muscle breakdown. 4. Therefore, choice B is correct as ketoacids play a crucial role in providing energy during starvation. Summary of why other choices are incorrect: A: Glycogen stores are depleted within 24 hours, not 48 hours. C: Hypoglycemia during starvation does not have a protein sparing effect. D: The average time until death from starvation is typically much shorter than 40 days.

Correct Answer: C

Rationale: The correct answer is C: negative feedback mechanism. This is because the majority of hormones in the endocrine system are regulated by a feedback loop that maintains homeostasis by inhibiting further hormone production when levels are too high and stimulating production when levels are too low. This negative feedback mechanism ensures that hormone levels remain within a narrow range. A: hormone-gene complex is incorrect as hormones are not primarily regulated by direct interactions with genes. B: hormone-receptor complex is incorrect as receptors are involved in hormone action, not regulation. D: positive feedback mechanism is incorrect as it would lead to an amplification of hormone production, which is not typically seen in the endocrine system to maintain stability.

Correct Answer: C

Rationale: The correct term for the digestive tract that begins at the mouth and finishes at the anus is called the alimentary canal. This term specifically refers to the entire passage through which food passes and is digested. The term "alimentary" pertains to nourishment or nutrition, making it the most accurate description of the digestive tract. A: Digestive passage is too broad and vague, not specifying the entire route of digestion. B: Elementary canal is not a commonly used term in anatomy to describe the digestive tract. D: Intestinal tract specifically refers to the section of the digestive system that includes the small and large intestines, excluding the mouth, esophagus, and stomach.