Lecture 18: Na+ and Water Balance

These flashcards cover key concepts related to Na+ and water balance, mechanisms of urine concentration, and hormonal regulation in the renal system.

What is the primary site of tubular reabsorption in the nephron?

The Proximal Convoluted Tubule (PCT).

What hormone increases water reabsorption in the collecting ducts?

Antidiuretic hormone (ADH).

What percentage of Na+ and water is reabsorbed in the proximal convoluted tubule?

Approximately 65% of Na+ and water.

What is the function of aldosterone in the renal system?

Aldosterone promotes sodium reabsorption in the collecting ducts and distal convoluted tubule, which increases blood pressure and decreases potassium levels.

What occurs when the transport maximum for glucose reabsorption is exceeded?

Glucose remains in the filtrate and is excreted in the urine.

Describe tubular secretion. What is its importance?

Tubular secretion is the process of moving selected substances from peritubular capillaries into the tubular fluid, important for disposing of drugs, eliminating undesirable substances, and controlling blood pH.

What is the countercurrent mechanism and its role in urine concentration?

It is the process where fluid flows in opposite directions in adjacent segments of the nephron, helping to maintain osmotic concentration and regulate urine volume.

How does dehydration affect urine production?

Dehydration results in the production of a small volume of concentrated urine.

What cells in the juxtaglomerular apparatus secrete renin?

Juxtaglomerular (JG)/granular cells in the wall of the afferent arteriole.

What impact does atrial natriuretic peptide (ANP) have on blood pressure and volume?

ANP reduces blood Na+, leading to decreased blood volume and blood pressure.

What is the role of parathyroid hormone (PTH) in the renal tubules?

PTH increases calcium reabsorption in the distal convoluted tubule.

What does maximal release of ADH result in?

It results in the production of a small volume of concentrated urine.

What is the osmolality of urine typically produced during overhydration?

Around 100 mOsm.

Describe the permeability characteristics of the thin descending limb of the nephron loop.

It is permeable to water but impermeable to solutes.

What is the result of water reabsorption in relation to urea concentration?

As water is reabsorbed, urea concentration in the tubular fluid increases.