1) Salt and Water Regulation

Which of the following is NOT a recognized function of the kidney?

Storage of bile for digestion

At any given time, what percentage of cardiac output do the kidneys receive?

20–25%

Which structure is responsible for filtration in the nephron?

Glomerulus

Why is the afferent arteriole's diameter larger than the efferent arteriole?

To generate a pressure gradient for filtration

What is the primary function of the vasa recta in the juxtamedullary nephron?

Create an osmotic gradient in the medulla

Which mechanisms contribute to renal autoregulation?

Myogenic response and tubuloglomerular feedback

What happens when macula densa cells detect low sodium chloride levels?

Vasodilation of afferent arteriole

Which of the following is NOT a layer of the glomerular filtration barrier?

Juxtaglomerular apparatus

Which of the following substances is typically excluded from the glomerular filtrate?

Albumin

What is the function of fixed negative charges in the glomerular filtration barrier?

Repel negatively charged proteins

Which best describes tubular secretion?

Active movement from capillary to tubular lumen

What is the correct sequence of urine formation?

Filtration → Reabsorption → Secretion

Why might albumin be found in urine after intense exercise?

Increased permeability of filtration barrier

Why is it important not to lose albumin in urine?

Albumin contributes to plasma oncotic pressure

What is the primary function of fenestrated endothelium in the glomerulus?

Prevent passage of blood cells

Why might albumin appear in urine after intense physical activity?

Increased glomerular permeability and higher pressure from arteriole constriction

What is the effect of losing negative charges from the glomerular filtration barrier?

Increased protein filtration into the urine

Which of the following is a clinical indicator of glomerular membrane damage?

Proteinuria

How does diabetic nephropathy impair kidney function?

Thickens filtration barrier via mesangial cell proliferation

What is the net filtration pressure (NFP) in the glomerulus, based on standard values?

10

Which two forces oppose glomerular blood hydrostatic pressure?

Capsular hydrostatic pressure and blood colloid osmotic pressure

Where does most selective reabsorption in the nephron occur?

Proximal convoluted tubule

What feature enhances the reabsorptive capacity of proximal tubule cells?

Extensive brush border with microvilli

What is the role of the sodium-potassium ATPase pump in tubular cells?

Pumps sodium out and potassium into the cell against gradients

Which process represents secondary active transport in the PCT?

Glucose reabsorption via sodium co-transport

Water reabsorption in the PCT primarily occurs via:

Osmosis through aquaporins

Which substance is reabsorbed via the paracellular route in the nephron?

Urea

Where is aquaporin-1 primarily found in the nephron?

Proximal tubule

Which describes transepithelial transport in the nephron?

Movement across a single cell from lumen to interstitium

What percentage of glucose is reabsorbed in a healthy nephron?

100%

What is the term for the maximum rate at which glucose can be reabsorbed by the nephron?

Transport maximum

Which condition occurs when glucose appears in the urine due to saturation of its transporters?

Glycosuria

What process leads to increased urine output due to unreabsorbed glucose dragging water into the tubule?

Osmotic diuresis

What is the primary site for the countercurrent mechanism in the nephron?

Loop of Henle

Which limb of the Loop of Henle is impermeable to water but allows active transport of salts?

Thick ascending limb

The countercurrent multiplier effect results in:

Concentration of urine by building a medullary osmotic gradient

What ion is secreted into the distal tubule as part of the kidney's regulatory function?

Potassium

Which hormone increases water reabsorption in the collecting duct?

Antidiuretic hormone (ADH)

ADH exerts its effect on which specific receptor in the collecting duct?

V2

Aquaporin-2 channels are inserted into the luminal membrane of the collecting duct in response to:

ADH binding to V2 receptors

What role do aquaporin-3 and aquaporin-4 channels play in the nephron?

They allow water to exit into the interstitium

What happens in response to dehydration in the body?

Osmoreceptors shrink, increasing ADH release

What is the term for increased sodium excretion in the urine?

Natriuresis

Which nephron structure primarily determines final urine concentration and volume?

Collecting duct

What stimulates aldosterone secretion in relation to potassium?

High potassium concentration

What is the primary determinant of extracellular fluid (ECF) volume?

Total body sodium content

A person excreting more sodium than they ingest is said to be in:

Negative sodium balance

Which of the following conditions is most likely to occur if sodium retention continues unchecked?

Oedema

What percentage of filtered sodium is typically reabsorbed by the proximal convoluted tubule?

67%

In which nephron segment is sodium reabsorption NOT accompanied by water reabsorption?

Thick ascending limb

Which of the following nephron segments is most responsible for the fine-tuning of sodium excretion?

Distal convoluted tubule and collecting duct

Sodium reabsorption in the thick ascending limb occurs via:

Na+/K+/2Cl− symporter

What is the approximate percentage of filtered sodium that is ultimately excreted in urine under normal conditions?

<1%

Which diuretic blocks the Na+/K+/2Cl− symporter in the thick ascending limb?

Furosemide

Bartter’s syndrome is associated with:

Impaired Na+/K+/2Cl− symporter

Which of the following statements about Gitelman’s syndrome is correct?

It causes hypocalciuria by enhancing calcium reabsorption

What is the mechanism by which thiazide diuretics reduce urinary calcium loss?

They increase calcium reabsorption in the distal tubule

Aldosterone acts primarily on which nephron segments?

Distal tubule and collecting duct

The sodium-hydrogen exchanger (NHE) plays a role in:

Acid-base balance and sodium reabsorption

What is the function of the sodium-potassium ATPase in renal tubular cells?

It actively transports sodium into the blood and potassium into the cell