Plasma makes up what percentage of extracellular fluid?

Correct Answer: B

Rationale: The correct answer is B (25 percent) because plasma constitutes around 20-25% of extracellular fluid. Plasma is the liquid component of blood and is part of the extracellular fluid. Option A (0 percent) is incorrect because plasma does make up a percentage of extracellular fluid. Option C (50 percent) and Option D (75 percent) are incorrect as they overestimate the percentage of extracellular fluid that plasma constitutes. Plasma, while important, is only a portion of the extracellular fluid in the body.

Correct Answer: C

Rationale: The correct answer is C: salt balance. Salt balance is crucial for maintaining extracellular fluid (ECF) volume as salt, specifically sodium, plays a key role in regulating fluid balance in the body. When salt intake is high, the body retains more water to maintain osmotic balance, increasing ECF volume. On the other hand, low salt intake can lead to decreased ECF volume due to water loss. Vasopressin secretion (A) regulates water reabsorption in the kidneys, not salt balance. Free water balance (B) is important but does not directly impact ECF volume maintenance. Potassium balance (D) is more relevant to intracellular fluid balance and membrane potential, not ECF volume regulation.

Correct Answer: C

Rationale: The correct answer is C because the renin-angiotensin-aldosterone system promotes an increase in arterial blood pressure by promoting Na+ reabsorption in the distal and collecting tubules. This leads to an increase in blood volume and subsequently an increase in blood pressure. The other choices are incorrect because: A: Water reabsorption through vasopressin release does not directly contribute to an increase in arterial blood pressure. B: The baroreceptor reflex helps regulate blood pressure by sensing changes and triggering appropriate responses, but it does not directly promote an increase in arterial blood pressure. D: Vasodilation of the afferent arteriole and increasing glomerular filtration rate actually lead to a decrease in blood pressure by reducing resistance in the kidneys.

Correct Answer: D

Rationale: The correct answer is D because osmolarity refers to the concentration of solutes in a solution. A hypertonic solution has a higher concentration of solutes compared to an isotonic solution, leading to water moving out of cells through osmosis. This definition directly relates to osmolarity. A, B, and C are incorrect as they do not directly relate to osmolarity. Choice A talks about vasopressin secretion in response to water deficit, B discusses urinary output in dehydration, and C is incomplete. These choices do not address the concept of osmolarity, which is about solute concentration in a solution.

Correct Answer: B

Rationale: Correct Answer: B (Ca2+) Rationale: In states of acidosis, the body retains Ca2+ in body fluids to help buffer the excess H+ ions and maintain pH balance. Ca2+ acts as a buffer by binding to excess H+ ions, reducing acidity. Kidneys increase Ca2+ retention to counteract the increased H+ secretion. This relationship helps stabilize the body's pH. Summary: A: Na+ is not directly involved in buffering excess H+ ions during acidosis. C: K+ is not specifically retained in response to increased H+ secretion. D: Cl- is not directly related to buffering and pH balance in acidosis.