Q.1 Which nephron structure is primarily responsible for filtration of blood?
Proximal tubule
Glomerulus
Loop of Henle
Collecting duct
Explanation - The glomerulus filters blood through its capillaries into Bowman’s capsule, initiating urine formation.
Correct answer is: Glomerulus
Q.2 Which force primarily drives glomerular filtration?
Osmotic pressure
Hydrostatic pressure in the glomerular capillaries
Colloid osmotic pressure in Bowman’s capsule
Active transport
Explanation - The high hydrostatic pressure in the glomerular capillaries drives plasma filtration into Bowman’s capsule.
Correct answer is: Hydrostatic pressure in the glomerular capillaries
Q.3 The majority of sodium reabsorption occurs in which part of the nephron?
Distal convoluted tubule
Collecting duct
Proximal convoluted tubule
Loop of Henle
Explanation - About 65–70% of sodium is reabsorbed in the proximal convoluted tubule with water and other solutes.
Correct answer is: Proximal convoluted tubule
Q.4 Which hormone increases water reabsorption in the collecting duct?
Aldosterone
Vasopressin (ADH)
Renin
Atrial natriuretic peptide
Explanation - ADH increases aquaporin insertion in collecting duct cells, enhancing water reabsorption.
Correct answer is: Vasopressin (ADH)
Q.5 Which cells secrete renin?
Mesangial cells
Podocytes
Macula densa cells
Juxtaglomerular cells
Explanation - Juxtaglomerular cells of the afferent arteriole secrete renin in response to low renal perfusion.
Correct answer is: Juxtaglomerular cells
Q.6 What is the normal glomerular filtration rate (GFR) in adults?
50 mL/min
100 mL/min
125 mL/min
200 mL/min
Explanation - The average GFR in healthy adults is about 125 mL/min (180 L/day).
Correct answer is: 125 mL/min
Q.7 Which part of the nephron generates the medullary concentration gradient?
Proximal tubule
Loop of Henle
Distal tubule
Collecting duct
Explanation - The countercurrent multiplier system of the Loop of Henle establishes the medullary gradient.
Correct answer is: Loop of Henle
Q.8 Which molecule is freely filtered at the glomerulus but neither reabsorbed nor secreted, making it ideal for measuring GFR?
Creatinine
Urea
Inulin
Glucose
Explanation - Inulin is not metabolized, reabsorbed, or secreted, making it the gold standard for GFR measurement.
Correct answer is: Inulin
Q.9 Which factor decreases GFR?
Increased afferent arteriole dilation
Increased efferent arteriole constriction
Decreased renal plasma flow
Increased glomerular capillary pressure
Explanation - A fall in renal plasma flow reduces glomerular capillary hydrostatic pressure, lowering GFR.
Correct answer is: Decreased renal plasma flow
Q.10 The countercurrent exchange system involves which structure?
Glomerulus
Vasa recta
Proximal tubule
Macula densa
Explanation - The vasa recta preserve the medullary concentration gradient by countercurrent exchange.
Correct answer is: Vasa recta
Q.11 Which ion is secreted in exchange for sodium in the distal nephron under aldosterone control?
Calcium
Chloride
Potassium
Bicarbonate
Explanation - Aldosterone stimulates sodium reabsorption and potassium secretion in the distal nephron.
Correct answer is: Potassium
Q.12 In renal physiology, Tm refers to:
Total metabolism
Tubular maximum
Transport molecule
Transmembrane migration
Explanation - Tm is the maximum rate at which a substance can be reabsorbed due to carrier saturation.
Correct answer is: Tubular maximum
Q.13 Glucose is normally completely reabsorbed in which nephron segment?
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
Explanation - Glucose is actively reabsorbed in the proximal tubule via sodium-glucose transporters.
Correct answer is: Proximal convoluted tubule
Q.14 Which ion is predominantly reabsorbed in the thick ascending limb of the Loop of Henle?
Sodium
Potassium
Calcium
Magnesium
Explanation - The thick ascending limb reabsorbs sodium via the Na-K-2Cl symporter and is impermeable to water.
Correct answer is: Sodium
Q.15 Which hormone stimulates sodium reabsorption in the distal tubule?
Cortisol
Aldosterone
ADH
Erythropoietin
Explanation - Aldosterone increases sodium reabsorption and potassium secretion in the distal nephron.
Correct answer is: Aldosterone
Q.16 The renal clearance of which substance is used to estimate renal plasma flow?
Inulin
Creatinine
PAH (para-aminohippuric acid)
Glucose
Explanation - PAH is almost completely excreted in urine, making it useful to estimate renal plasma flow.
Correct answer is: PAH (para-aminohippuric acid)
Q.17 What is the main site of ammonium ion secretion?
Proximal tubule
Distal tubule
Collecting duct
Glomerulus
Explanation - Ammonium is secreted in the proximal tubule, aiding acid excretion and buffering urine.
Correct answer is: Proximal tubule
Q.18 Which transporter is inhibited by loop diuretics?
Na-Cl symporter
Na-K-2Cl symporter
Na-K ATPase
Aquaporins
Explanation - Loop diuretics inhibit the Na-K-2Cl symporter in the thick ascending limb.
Correct answer is: Na-K-2Cl symporter
Q.19 Which renal structure senses sodium concentration in the filtrate?
Juxtaglomerular cells
Macula densa
Mesangial cells
Podocytes
Explanation - Macula densa cells in the distal tubule sense sodium and help regulate GFR and renin release.
Correct answer is: Macula densa
Q.20 Which buffer system is most important in renal tubular fluid?
Phosphate buffer
Bicarbonate buffer
Protein buffer
Ammonia buffer
Explanation - The ammonia buffer system is crucial for excreting hydrogen ions in the kidney.
Correct answer is: Ammonia buffer
Q.21 Which part of the nephron is impermeable to water?
Proximal tubule
Descending limb of Loop of Henle
Thick ascending limb of Loop of Henle
Collecting duct (with ADH)
Explanation - The thick ascending limb reabsorbs solutes but is impermeable to water, helping dilute urine.
Correct answer is: Thick ascending limb of Loop of Henle
Q.22 Which condition increases renin secretion?
Hypertension
Increased sodium intake
Low renal perfusion pressure
Increased blood volume
Explanation - Renin is secreted in response to low renal perfusion pressure or low sodium delivery.
Correct answer is: Low renal perfusion pressure
Q.23 What is the normal renal threshold for glucose reabsorption?
50 mg/dL
100 mg/dL
180 mg/dL
250 mg/dL
Explanation - Glucose appears in urine when plasma levels exceed ~180 mg/dL, the renal threshold.
Correct answer is: 180 mg/dL
Q.24 Which factor causes constriction of the afferent arteriole and reduces GFR?
Prostaglandins
Nitric oxide
Angiotensin II (at high concentration)
ANP
Explanation - High levels of Angiotensin II constrict both afferent and efferent arterioles, reducing GFR.
Correct answer is: Angiotensin II (at high concentration)
Q.25 Which renal hormone stimulates red blood cell production?
Renin
Erythropoietin
Aldosterone
ADH
Explanation - Erythropoietin, produced by interstitial cells of the kidney, stimulates erythropoiesis.
Correct answer is: Erythropoietin