Which one of the following hormones is released by both the stomach and small intestine?

Correct Answer: A

Rationale: Rationale: 1. Gastrin is released by the stomach to stimulate gastric acid secretion. 2. Gastrin is also released by the small intestine to regulate digestive processes. 3. Secretin is released by the small intestine to stimulate bicarbonate secretion. 4. Cholecystokinin is released by the small intestine to stimulate bile release. 5. Gastric inhibitory polypeptide is released by the small intestine to inhibit gastric acid secretion. Summary: A: Gastrin is the correct answer as it is released by both the stomach and small intestine. B: Secretin is only released by the small intestine. C: Cholecystokinin is only released by the small intestine. D: Gastric inhibitory polypeptide is only released by the small intestine.

Correct Answer: C

Rationale: The correct answer is C: brush border of the small intestine. Disaccharides are broken down into monosaccharides by specific enzymes located in the brush border of the small intestine. These enzymes include sucrase, lactase, and maltase. The breakdown of disaccharides into monosaccharides occurs in the final stage of carbohydrate digestion, allowing for absorption into the bloodstream. Choices A, B, and D are incorrect because disaccharides are not primarily digested in the stomach, the lumen of the small intestine, or the colon. The main site for disaccharide digestion is the brush border of the small intestine where these specific enzymes are located.

Correct Answer: A

Rationale: The correct answer is A because the absorption of glucose is indeed associated with sodium uptake. This process occurs through the sodium-glucose cotransporter located on the apical membrane of the enterocytes in the small intestine. Sodium acts as a co-transporter, helping to facilitate the absorption of glucose. This mechanism is crucial for efficient absorption of glucose in the GI tract. Choice B is incorrect as glucose is actually absorbed more rapidly than fructose due to differences in transport mechanisms. Choice C is incorrect since galactose and fructose are absorbed by different transporters at the brush border membrane. Choice D is also incorrect because the majority of water absorption occurs in the small intestine, not the colon.

Correct Answer: D

Rationale: Step 1: Reuptake of the transmitter at the presynaptic terminal: This process involves the retrieval of excess neurotransmitter molecules back into the presynaptic neuron, preventing excessive accumulation in the synapse. Step 2: Enzymatic degradation of the transmitter within the synapse: Enzymes break down excess neurotransmitter molecules in the synapse, helping to maintain optimal levels and preventing overstimulation of the post synaptic terminal. Step 3: Negative feedback to inhibit further release of the transmitter: When neurotransmitter levels are high, negative feedback mechanisms can inhibit further release, preventing excessive accumulation and maintaining synaptic balance. Summary: - Option A and B are correct because reuptake and enzymatic degradation help prevent excessive accumulation of neurotransmitters. - Option C is also correct as negative feedback mechanisms play a role in regulating neurotransmitter release. - Therefore, the correct answer is D, as all of the above mechanisms work together to prevent excessive accumulation of neurotransmitters.

Correct Answer: C

Rationale: The correct answer is C because during moderate exercise, your body primarily relies on glycogen stores, not protein stores, for energy. Protein is not a preferred energy source during exercise as it is mainly used for structural and enzymatic functions. Muscle glycogen, muscle triglycerides, and plasma fatty acids are the main sources of energy at 65% VO2 max. Low-intensity exercise primarily utilizes fatty acids from plasma. Blood glucose stores can be depleted within about 15 minutes of very intense exercise due to high energy demands. Thus, choice C is false as protein stores are not the biggest energy source during moderate exercise.