The stomach contractions, which move the chyme from near the periphery of the stomach toward the pyloric sphincter, are called

Correct Answer: C

Rationale: The correct answer is C: mixing waves. Mixing waves are the stomach contractions that help mix the chyme near the periphery of the stomach and move it towards the pyloric sphincter for further digestion. Peristaltic waves (B) are rhythmic contractions that propel food through the digestive system, not specifically in the stomach. The pyloric pump (A) is not a recognized term in gastrointestinal physiology. Mass movements (D) refer to contractions in the large intestine that move feces towards the rectum, not in the stomach.

Correct Answer: A

Rationale: The correct answer is A: lactose intolerance. This is due to the inability to digest lactose, the sugar found in dairy products, leading to symptoms like intestinal cramps, bloating, and diarrhea. This is a common condition caused by a deficiency of lactase enzyme. Choice B: Diabetes mellitus, Type I, is incorrect as it is an autoimmune condition affecting insulin production, not digestion of dairy products. Choice C: Heartburn is incorrect as it is a symptom of acid reflux, not related to dairy product intolerance. Choice D: Peritonitis is incorrect as it is an inflammation of the abdominal lining, usually caused by infection or injury, not related to dairy product intolerance.

Correct Answer: D

Rationale: The correct answer is D because the presence of folds, villi, and microvilli on the surface of enterocytes significantly increases the absorptive area of the intestine. The folds increase the surface area, villi further increase the surface area, and microvilli further amplify the absorptive surface. This intricate structure allows for efficient absorption of nutrients. Option A is incorrect as the absorptive area is not equivalent to a tennis court. Option B is incorrect because not all options are correct. Option C is incorrect because changes in motility can affect nutrient absorption but do not directly relate to the absorptive area of the intestine like the structural features mentioned in option D.

Correct Answer: B

Rationale: Rationale: Choice B is correct because GABA is indeed released by GABA neurons and acts to inhibit the propagation of signals triggered by dopamine in the post-synaptic neuron. GABA functions as an inhibitory neurotransmitter in the central nervous system. Choices A and C are incorrect. Choice A is inaccurate because GABA inhibits the release of dopamine, not the other way around. Choice C is incorrect as heroin and morphine act on opioid receptors, not GABA receptors. Choice D is incorrect because not all statements are true.

Correct Answer: B

Rationale: The correct answer is B because SNPs are actually a common source of genetic polymorphisms, occurring frequently in the human genome. SNPs are variations in a single nucleotide base and are estimated to occur once every 300 nucleotides. Choice A is incorrect because of this high frequency. Choice C is also incorrect as certain SNPs can indeed impact gene expression and health outcomes. Choice D is incorrect because B is not true, making the statement false. In summary, B is the correct answer as SNPs are not rare but rather common genetic variations in humans.