Which of these statements does NOT refer to the relationship between plasma and interstitial fluid?

Correct Answer: D

Rationale: The correct answer is D because plasma and interstitial fluid are in dynamic equilibrium and do exchange materials through capillary walls. Changing the composition of one affects the other due to this exchange. Choice A is incorrect because plasma and interstitial fluid have some differences. Choice B is incorrect as capillary walls allow for exchange. Choice C is incorrect as proteins are restricted from freely passing through capillary walls.

Correct Answer: B

Rationale: Correct Answer: B - Decreased K+ in the ECF Rationale: 1. Renin is released by the kidneys in response to decreased arterial blood pressure (A), decreased plasma volume (C), and decreased Na+ in the ECF (D). 2. Aldosterone release is stimulated by decreased plasma volume and decreased Na+ in the ECF, but not by decreased K+ in the ECF. 3. The renin-angiotensin-aldosterone system is primarily involved in regulating Na+ and water balance, not K+ levels. Summary: A, C, and D are incorrect because they can trigger the renin-angiotensin-aldosterone system. Choice B is the correct answer as decreased K+ levels do not directly activate this system.

Correct Answer: A

Rationale: Step 1: Increased ECF osmolarity causes osmoreceptors to detect the change. Step 2: Osmoreceptors signal the hypothalamus to release ADH (vasopressin). Step 3: ADH increases water reabsorption in the kidneys. Step 4: Water shifts from the ICF into the ECF to restore osmotic balance. Therefore, choice A is correct. Choices B and C are incorrect because changes in osmolarity trigger water movement. Choice D is incorrect because vasopressin secretion would actually increase to help restore water balance.

Correct Answer: B

Rationale: The correct answer is B: disorientation and coma. Acidosis occurs when the body's pH level becomes too acidic. This leads to central nervous system dysfunction, resulting in disorientation and potentially coma. Extreme nervousness (A) is not a typical symptom of acidosis. "Pins and needles" sensations (C) are more commonly associated with nerve damage or circulation issues. Muscle twitches and spasms (D) are not specific to acidosis and can occur due to various reasons. In summary, disorientation and coma are key indicators of acidosis due to the impact on the central nervous system.

Correct Answer: C

Rationale: The primary buffer system in the extracellular fluid (ECF) is the bicarbonate/carbonic acid system. This system helps maintain the pH of the blood within a narrow range by accepting or releasing hydrogen ions. Carbonic acid can donate hydrogen ions to lower pH, while bicarbonate can accept hydrogen ions to raise pH. Haemoglobin primarily functions as an oxygen transporter in the blood and does not play a significant role as a buffer in the ECF. Chloride/hydrochloric acid is more involved in the stomach's acidic environment and is not a primary buffer system in the ECF. Phosphate is a buffer system mainly found in the intracellular fluid and urine, not in the ECF. Therefore, option C is the correct answer as it is the primary buffer system in the ECF, while the other options are not as directly involved in maintaining the ECF pH balance.