Which of the following is true regarding the proximal tubule?

Correct Answer: B

Rationale: In the proximal tubule, reabsorption is isosmotic, meaning water and solutes (e.g., Na⁺, Cl⁻) are reabsorbed in proportion, maintaining filtrate osmolarity similar to plasma (300 mOsm/L). The epithelium is leaky and permeable (A is false), Na⁺ moves transcellularly and paracellularly (C is false), and Cl⁺ concentrates in the lumen (D is false), making B true.

Correct Answer: C

Rationale: After IV sedation for a bronchoscopy, monitoring vital signs like blood pressure and heart rate (C) is critical to assess sedation effects and ensure stability, a key LPN task. Education (A) is the RN's role pre-sedation, water (B) risks aspiration (NPO status), and bathroom (D) is impractical post-sedation, making C the appropriate instruction.

Correct Answer: D

Rationale: Urea, a waste product from protein breakdown, is filtered and excreted by the kidneys. Regular monitoring (e.g., blood urea nitrogen, BUN) evaluates kidney health (D), as impaired function raises levels (e.g., renal failure). Liver disorders (A) affect urea production, metabolic health (B) is vague, and deficiencies (C) aren't a concern, making D correct.

Correct Answer: D

Rationale: The proximal tubule reabsorbs ~65% of filtrate iso-osmotically (A), PAH concentration rises as it's secreted (B is false), and glucose/bicarbonate are mostly reabsorbed (C). A and C are true—reabsorption is iso-osmotic, nutrients are reclaimed—while B is incorrect, making D (A and C are correct) the answer.

Correct Answer: B

Rationale: Rising pCO₂ (80 mmHg) from hypoventilation lowers blood pH (acidosis) rapidly. CSF pH falls faster as CO₂ diffuses quickly across the blood-brain barrier, outpacing blood buffering (e.g., HCO₃⁻). Blood pH lags due to systemic buffers, making B correct.