Kidney Function and ADH

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Questions and Answers

A 62-year-old woman with a prior unilateral nephrectomy has a GFR of 50 ml/min and a plasma glucose concentration of 200 mg/100 ml. If her kidney's transport maximum for glucose is 150 mg/min, what is her approximate rate of glucose excretion?

  • 150 mg/min
  • 0 mg/min (correct)
  • 50 mg/min
  • 100 mg/min

In a racing greyhound experiencing dehydration, antidiuretic hormone (ADH) is released. Which portion of the nephron tubule is primarily affected by ADH to increase water reabsorption?

  • Ascending limb of the loop of Henle
  • Early distal tubule
  • Collecting duct (correct)
  • Proximal tubule

Given a glomerular hydrostatic pressure of 60 mm Hg, Bowman's space hydrostatic pressure of 20 mm Hg, and glomerular capillary colloid osmotic pressure of 35 mm Hg, what is the net pressure driving glomerular filtration?

  • 10 mm Hg
  • 5 mm Hg (correct)
  • 15 mm Hg
  • 0 mm Hg

Calculate the filtration fraction, given a glomerular filtration rate (GFR) of 150 mL/min and a renal plasma flow of 480 mL/min.

<p>0.31 (A)</p> Signup and view all the answers

Which of the following changes would most likely increase the glomerular filtration rate (GFR)?

<p>A 50% decrease in afferent arteriolar resistance (B)</p> Signup and view all the answers

A vasodilator drug causes a 50% decrease in efferent arteriolar resistance, with no change in arterial pressure. How would this impact renal blood flow (RBF), glomerular filtration rate (GFR), and filtration fraction (FF)?

<p>RBF: Increase, GFR: Decrease, FF: Decrease (A)</p> Signup and view all the answers

What triggers the micturition reflex, leading to the urge to urinate?

<p>Distension of the bladder wall detected by stretch receptors (A)</p> Signup and view all the answers

In response to acidic blood pH, aldosterone production increases. How does aldosterone help resolve this acidity in the kidneys, specifying the cell type and nephron location?

<p>By activating H+ secretion and HCO3- reabsorption in the intercalated type A cells of the late distal tubule (A)</p> Signup and view all the answers

The secretion of H+ into the nephron in response to acidic blood pH is an example of which renal process?

<p>Secretion (A)</p> Signup and view all the answers

A patient's renal plasma flow is determined to be 600 ml/min, and their urine flow rate is 5 ml/min. If the concentration of substance X in their plasma is 1 mg/ml and in their urine is 150 mg/ml, what is the approximate clearance of substance X?

<p>750 ml/min (B)</p> Signup and view all the answers

Which of the following scenarios would lead to the greatest increase in potassium excretion?

<p>Increased activity of the Na+/K+ ATPase pump in the distal tubule cells (D)</p> Signup and view all the answers

A person consumes a large amount of sodium chloride (NaCl). How would the kidneys respond to maintain sodium balance?

<p>Decrease sodium reabsorption in the collecting duct (A)</p> Signup and view all the answers

What effect does increased parathyroid hormone (PTH) have on phosphate handling by the kidneys?

<p>Decreased phosphate reabsorption in the proximal tubule (D)</p> Signup and view all the answers

Which of the following factors would lead to an increase in renin secretion by the granular cells of the afferent arteriole?

<p>Increased sympathetic nerve activity (B)</p> Signup and view all the answers

A patient is experiencing metabolic acidosis. How will the kidneys compensate for this condition?

<p>By increasing the secretion of H+ ions (D)</p> Signup and view all the answers

Flashcards

Glucose Excretion Rate

Glucose excretion rate is approximately 0 mg/min because the kidneys reabsorb all filtered glucose.

ADH Effect on Tubule

ADH increases water reabsorption in the collecting duct, reducing dehydration.

Net Filtration Pressure

Net pressure is glomerular hydrostatic pressure minus colloid osmotic pressure minus Bowman's capsule hydrostatic pressure.

Filtration Fraction Calculation

Filtration fraction equals GFR divided by renal plasma flow.

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Effect on GFR

A 50% decrease in afferent arteriolar resistance increases glomerular filtration rate.

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Efferent Arteriole Vasodilation

A vasodilator affecting the efferent arteriole increases renal blood flow, decreases GFR, and filtration fraction.

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Micturition Reflex

Stretch receptors activate, sending signals to the spinal cord, causing detrusor muscle contraction and the urge to urinate.

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Aldosterone's Function

Aldosterone stimulates H+ secretion and reabsorbs HCO3- in intercalated type A cells of the late distal tubule.

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H+ handling process

Secretion

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Study Notes

  • A 62-year-old woman with a unilateral nephrectomy has a GFR of 50 ml/min, urine flow rate of 2.0 ml/min, and plasma glucose of 200 mg/100 ml.
  • Her kidney transport maximum for glucose is 150 mg/min.
  • Her approximate rate of glucose excretion is 0 mg/min.
  • To determine glucose excretion, you must find the difference between filtered glucose and the transport maximum.
  • GFR (50 ml/min) multiplied by plasma glucose concentration (2 mg/ml) equals 100 mg/min of filtered glucose.
  • 100 mg/min (filtered glucose) minus 150 mg/min (transport maximum) equals -50 mg/min.
  • All glucose in the filtrate is reabsorbed, so there is 0 mg/min lost in excretion despite having only one kidney.

ADH and the Kidney

  • ADH is released in a racing greyhound as it becomes dehydrated.
  • ADH affects the late distal tubule and collecting duct of the nephron.
  • ADH increases the permeability to water reabsorption in these areas.
  • This action puts water back into circulation, reducing dehydration.

Glomerular Filtration Pressure

  • Average hydrostatic pressure in glomerular capillaries: 60 mm Hg.
  • Hydrostatic pressure in Bowman's space: 20 mm Hg.
  • Average colloid osmotic pressure in glomerular capillaries: 35 mm Hg.
  • Net pressure driving glomerular filtration is 5 mm Hg.
  • Net pressure = Glomerular hydrostatic pressure – Colloid osmotic pressure – Bowman’s hydrostatic pressure.
  • Net pressure = 60 mm Hg - 35 mm Hg - 20 mm Hg.

Filtration Fraction Calculation

  • Glomerular filtration rate (GFR) is 150 mL/min.
  • Renal plasma flow is 480 mL/min.
  • Filtration fraction is 0.31.
  • Filtration fraction is calculated by GFR/Renal plasma flow.
  • Filtration fraction = 150/480.
  • Glomerular hydrostatic pressure is irrelevant for this calculation.

Glomerular Filtration Rate (GFR)

  • A 50% decrease in afferent arteriolar resistance would increase GFR.
  • A 50% decrease in efferent arteriolar resistance would decrease hydrostatic pressure in the glomerulus.
  • Decreased systemic blood pressure would decrease renal blood flow.
  • Increased hydrostatic pressure in Bowman’s capsule would increase net fluid movement into the glomerulus against filtration.

Vasodilator Effects on Renal Function

  • A vasodilator drug causes a 50% decrease in efferent arteriolar resistance.
  • Arterial pressure remains unchanged.
  • Renal blood flow increases.
  • GFR decreases.
  • Filtration fraction decreases.
  • GFR falls without any change in arterial pressure.
  • Filtration fraction (GFR/RBF) decreases due to the GFR decrease.

Micturition Reflex

  • Urine distension activates stretch receptors in the bladder wall.
  • Sensory neurons transmit signals to the sacrum of the spine via parasympathetic fibers.
  • Parasympathetic neurons return to the bladder.
  • This causes the detrusor muscle in the bladder wall to contract.
  • Contraction puts pressure on the urine, forcing it into the proximal urethra, creating the urge to urinate.
  • The detrusor muscle then relaxes, allowing more urine to flow into the bladder until the next reflex.
  • Urination occurs if the urethral sphincter relaxes.

Aldosterone and Acid-Base Balance

  • Excess H+ in the blood triggers increased aldosterone production.
  • Aldosterone functions in the late distal tubule.
  • Aldosterone activates the exchange of secreting H+ and reabsorbing HCO3- in the intercalated type A cells.
  • The exchange helps the body eliminate excess H+ by reabsorbing HCO3- and secreting H+ into the filtrate for excretion in the urine.
  • This is a specific example of secretion with regards to H+.

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