How do the baroreceptor reflexes affect sodium balance?

Correct Answer: C

Rationale: The correct answer is C because baroreceptor reflexes respond to changes in blood pressure by causing vasoconstriction of afferent arterioles, which decreases glomerular filtration rate (GFR) and enhances sodium reabsorption to maintain blood pressure. This mechanism helps regulate sodium balance. A: Release of renin is regulated by the renin-angiotensin-aldosterone system, not baroreceptor reflexes. B: Vasopressin release is primarily regulated by osmoreceptors in the hypothalamus, not baroreceptor reflexes. D: Vasodilation of afferent arterioles would increase GFR and potentially decrease sodium reabsorption, counteracting sodium balance regulation.

Correct Answer: B

Rationale: The correct answer is B: acidaemia. A pH of 7.3 in the blood indicates an acidic environment, as it is below the normal range of 7.35-7.45. Acidaemia specifically refers to the presence of excess acid in the blood. Choice A, acidosis, refers to a systemic condition of excess acid in the body, not just in the blood. Choice C, alkalosis, is the opposite of acidosis and describes a condition of excess base in the body. Choice D, alkalaemia, is not a recognized term in medical literature and is not used to describe a pH of 7.3 in the blood.

Correct Answer: B

Rationale: The correct answer is B: phospholipid buffering system. Phospholipids are not involved in buffering pH in the body. The other options (A: haemoglobin, C: phosphate, D: protein) are all known chemical buffering systems within the body. Haemoglobin acts as a buffer by binding to and releasing hydrogen ions, phosphate buffering system helps maintain pH balance in the intracellular and extracellular fluids, and proteins like albumin and histidine residues in proteins can act as buffers by accepting or donating protons to regulate pH levels. Therefore, phospholipids do not play a role in chemical buffering systems in the body, making option B the correct answer.

Correct Answer: A

Rationale: The correct answer is A: phosphate. Phosphate is a potent urinary buffer as it helps maintain the acid-base balance in the body by accepting or donating hydrogen ions in the urine. Phosphate plays a crucial role in regulating the pH of urine, making it an effective urinary buffer. Summary: - Phosphate is a potent urinary buffer as it helps regulate the pH of urine. - Haemoglobin is not a urinary buffer, it mainly functions in oxygen transport. - Bicarbonate/carbonic acid primarily acts as an extracellular buffer in the blood, not in the urine. - Proteins do have buffering capacity, but they are not specific to urinary buffering.

Correct Answer: C

Rationale: Rationale for Correct Answer (C): 1. Chemical buffers work quickly but may not be sufficient for rapid or large pH changes. 2. Kidneys can regulate acid-base balance by adjusting excretion of H+ and HCO3-. 3. Kidneys can respond immediately to maintain acid-base homeostasis. 4. Therefore, kidneys participate in acid-base balance to provide a rapid and effective response. Summary of Incorrect Choices: A. Incorrect because chemical buffers can act throughout the body, including the ECF around the kidneys. B. Incorrect because chemical buffers can buffer against various pH changes, not just those from increased HCO3-. D. Incorrect because chemical buffers can also bind to other ions, not just H+, and kidneys do not remove H+ entirely from the body.