What separates the two types of extracellular fluid?

Correct Answer: C

Rationale: The correct answer is C, blood vessel walls. Blood vessel walls separate the two types of extracellular fluid - interstitial fluid and blood plasma. This separation is crucial for maintaining homeostasis by regulating the exchange of nutrients, gases, and waste products between the bloodstream and surrounding tissues. The plasma membrane (choice A) is the boundary between the intracellular and extracellular environments of individual cells, not between the two types of extracellular fluid. The blood-brain barrier (choice B) is a specialized structure that separates the blood from the brain's extracellular fluid to protect the brain from harmful substances, not the two types of extracellular fluid. Transcellular membranes (choice D) refer to specific membranes within cells, not the separation between extracellular fluid types.

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: C

Rationale: When a cell is placed in an isotonic solution, the concentration of solutes inside and outside the cell is equal. This balance results in no net movement of water across the cell membrane, leading to the cell maintaining its normal shape and size. Choice A is incorrect because in a hypertonic solution, a cell will shrink due to water leaving the cell. Choice B is incorrect as in a hypotonic solution, a cell will swell due to water entering the cell. Choice D is incorrect as it does not provide any relevant information. Therefore, choice C is the correct answer as the cell will stay the same size in an isotonic solution.

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.