Which of these statements describes chemical buffer systems?

Correct Answer: B

Rationale: The correct answer is B: Chemical buffer systems respond to changes in acid or base levels. This is because chemical buffer systems work by absorbing or releasing H+ ions to maintain a stable pH in the body. They act immediately to prevent drastic changes in pH levels. A is incorrect because chemical buffer systems act almost instantaneously, not in one to three minutes. C is incorrect because chemical buffer systems do not directly promote H+ excretion by the kidneys; that is the role of the renal system. D is incorrect because chemical buffer systems do not directly stimulate the respiratory center; that is the role of the respiratory system.

Correct Answer: D

Rationale: Buffering of urine is important to prevent acidosis because if urine becomes too acidic, it prevents tubular secretion of H+ ions, limiting the renal buffering capacity. This helps maintain the body's acid-base balance. Choices A, B, and C are incorrect because they do not directly relate to the role of buffering urine in preventing acidosis. Choice A is incorrect because bicarbonate secretion is a mechanism to counteract acidosis, not a reason for buffering urine. Choice B is incorrect as acidic urine does not directly inhibit the micturition reflex. Choice C is incorrect because acidic urine does not typically damage the urinary bladder.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Vomiting leads to loss of fluids and electrolytes, causing dehydration. 2. Loss of stomach acid (HCl) during vomiting can result in metabolic alkalosis. 3. Dehydration leads to increased concentration of HCO3- in the blood, causing metabolic acidosis. 4. Therefore, vomiting can lead to dehydration and metabolic acidosis (Choice C). Summary: - Choice A is incorrect as vomiting leads to loss of H+ ions, not abnormal buildup. - Choice B is incorrect as vomiting does not lead to a decrease in HCO3-. - Choice D is incorrect as vomiting typically leads to metabolic acidosis, not alkalosis.

Correct Answer: B

Rationale: The correct answer is B because faster, deeper respirations help to eliminate excess CO2, which reduces the concentration of H+ ions in the blood, thus increasing pH. This compensates for the change in [H+] and helps maintain pH balance. Slower, shallower respirations (choice C) would not effectively eliminate CO2, leading to a buildup of H+ ions and a decrease in pH. Slower, deeper respirations (choice D) would also not effectively eliminate CO2, and the depth of respiration alone does not directly impact pH regulation. Choice A is incorrect because the respiratory mechanism plays a crucial role in pH control through the elimination of CO2.

Correct Answer: A

Rationale: Step 1: Plasma contains various substances like water, electrolytes, hormones, and nutrients. Step 2: The input of these substances is mainly determined by factors like diet, metabolism, and hormonal regulation. Step 3: Therefore, the overall input of substances in plasma is not extensively controlled. Step 4: Choice A (TRUE) is correct because the input of substances in plasma is not highly regulated. Step 5: Choices B, C, and D are incorrect as they do not align with the fact that the input of substances in plasma is not tightly controlled.