Glomerular Filtration and Starling Forces
34 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What remains in the blood as fluid filters out of the glomerular capillary?

  • Electrolytes
  • Red blood cells
  • Glucose
  • Proteins (correct)

    • What happens to the πGC at the end of the glomerular capillary?

  • It fluctuates randomly.
  • It decreases significantly.
  • It remains constant.
  • It increases. (correct)

    • Which Starling pressure primarily affects the glomerular filtration rate (GFR)?

  • Hydrostatic pressure in Bowman's capsule
  • Hydrostatic pressure in the glomerular capillary (correct)
  • Colloid osmotic pressure in Bowman's capsule
  • Venous pressure

    • What is the effect of constricting the afferent arteriole on GFR?

    <p>Decreases GFR due to reduced blood flow.</p> Signup and view all the answers

    What influences changes in PGC (hydrostatic pressure in the glomerular capillary)?

    <p>Changes in the resistance of the afferent and efferent arterioles.</p> Signup and view all the answers

    What remains constant in the patient's GFR measurement despite an increase in urine flow?

    <p>The GFR value</p> Signup and view all the answers

    How is the clearance of inulin and creatinine calculated?

    <p>By multiplying urine concentration by urine flow rate and dividing by plasma concentration</p> Signup and view all the answers

    What does GFR primarily represent in renal physiology?

    <p>Filtration rate of plasma in the kidneys</p> Signup and view all the answers

    What effect does drinking large volumes of water have on GFR when inulin infusion remains constant?

    <p>It has no effect on GFR</p> Signup and view all the answers

    Why is creatinine used clinically to assess kidney function?

    <p>It is a constant product of muscle metabolism that is filtered</p> Signup and view all the answers

    Which of the following statements about inulin is true?

    <p>Inulin must be infused intravenously for measurement</p> Signup and view all the answers

    If a patient's [U] inulin decreases while [P] inulin stays the same, what happens to GFR?

    <p>GFR remains the same</p> Signup and view all the answers

    What is renal plasma flow (RPF) fundamentally related to?

    <p>The relationship between GFR and the filtration fraction</p> Signup and view all the answers

    What is the normal filtration fraction for renal plasma flow?

    <p>20%</p> Signup and view all the answers

    What does renal clearance measure?

    <p>The volume of plasma completely cleared of a substance by the kidneys per unit time</p> Signup and view all the answers

    When a substance has a high renal clearance, what does this imply?

    <p>The substance is removed efficiently with a single pass through the kidneys</p> Signup and view all the answers

    Which of the following substances is likely to have a low renal clearance?

    <p>Albumin</p> Signup and view all the answers

    How is renal clearance calculated?

    <p>Clearance = Urinary excretion rate / Plasma concentration</p> Signup and view all the answers

    What happens to the 80% of renal plasma flow that is not filtered?

    <p>It leaves the glomerular capillaries via the efferent arterioles</p> Signup and view all the answers

    In the given sample problem, what is the plasma concentration of sodium (Na+)?

    <p>140 mEq/L</p> Signup and view all the answers

    If a patient collects 1.44 L of urine over 24 hours, what is the urine flow rate per hour?

    <p>0.12 L/h</p> Signup and view all the answers

    What effect does constriction of the efferent arteriole have on glomerular filtration rate (GFR)?

    <p>It increases the GFR by raising glomerular capillary pressure.</p> Signup and view all the answers

    Which factor primarily results in changes to the hydrostatic pressure in the glomerular capillary (PGC)?

    <p>Variations in afferent and efferent arteriolar resistance.</p> Signup and view all the answers

    What is a primary characteristic of a marker used to measure glomerular filtration rate (GFR)?

    <p>It must be freely filtered across the glomerular capillaries and not be reabsorbed.</p> Signup and view all the answers

    Why is inulin considered a good marker for measuring GFR?

    <p>It is large, uncharged, and does not bind to plasma proteins.</p> Signup and view all the answers

    What is the primary outcome when there are low levels of angiotensin II?

    <p>Decreased efferent arteriole resistance and reduced GFR.</p> Signup and view all the answers

    Which statement about glomerular filtration is true?

    <p>GFR is the final step in urine formation.</p> Signup and view all the answers

    What is the main role of Starling forces in kidney physiology?

    <p>To influence glomerular filtration and net ultrafiltration pressure.</p> Signup and view all the answers

    What happens to renal blood flow (RPF) when the efferent arteriole is constricted?

    <p>RPF decreases due to reduced outflow from the glomeruli.</p> Signup and view all the answers

    Which equation correctly represents the relationship between GFR and Starling forces?

    <p>GFR = Kf [(PGC - PBS) - πGC]</p> Signup and view all the answers

    What is a potential impact of elevated hydrostatic pressure in the glomerular capillaries?

    <p>Increased production of urine due to higher GFR.</p> Signup and view all the answers

    What happens to the oncotic pressure of glomerular capillary blood if unfiltered proteins increase?

    <p>It increases, raising the oncotic pressure.</p> Signup and view all the answers

    Which statement accurately describes the filtration fraction?

    <p>Filtration fraction is GFR divided by RPF.</p> Signup and view all the answers

    If the filtered load of a substance is less than its excretion rate, what is likely occurring?

    <p>The substance is being reabsorbed.</p> Signup and view all the answers

    Study Notes

    Glomerular Filtration

    • Proteins are left behind when fluid filters out of the glomerular capillary blood
    • Glomerular capillary hydrostatic pressure (PGC) and glomerular colloid osmotic pressure (πGC) increase with filtration of fluid
    • Net ultrafiltration pressure becomes 0 by the end of the glomerular capillary

    Starling Forces

    • Starling forces drive glomerular filtration rate (GFR)
    • Changes in PGC are due to changes in the resistance of the afferent and efferent arterioles
    • Constriction of the afferent arteriole increases resistance and reduces GFR
    • Vasoconstriction of the afferent arteriole can happen with an increase in the sympathetic nervous system activity or high levels of angiotensin II
    • Constriction of the efferent arteriole increases resistance and increases GFR
    • Vasoconstriction of the efferent arteriole can happen with low levels of angiotensin II

    GFR Measurement

    • Glomerular filtration rate (GFR) is a marker for nephron function
    • Measured using the clearance of a glomerular marker
    • A glomerular marker is freely filtered across the glomerular capillaries, is not reabsorbed or secreted by the renal tubule, and does not alter the GFR
    • Inulin is a good marker for GFR as it is freely filtered across the glomerular capillary wall and is neither reabsorbed nor secreted by renal tubular cells
    • The amount of inulin filtered across the glomerular capillaries equals the amount excreted in urine
    • Inulin must be infused intravenously, as it is not found endogenously
    • Clearance of inulin equals GFR, which further equals excretion rate of inulin or creatinine
    • Creatinine is used clinically to measure GFR, as it is a product of muscle metabolism, it is filtered and not reabsorbed or secreted

    GFR Equation

    • GFR = [U]inulin/Cr x V = Cinulin/Cr
      • [U]inulin/Cr: [inulin or creatinine] in urine
      • V = Urine flow rate
      • [P]inulin/Cr: [inulin or creatinine] in plasma
      • Cinulin/Cr: clearance of inulin or creatinine

    Filtration Fraction

    • Filtration fraction is the relationship between GFR and RPF
    • Filtration fraction is the fraction of RPF filtered across the glomerular capillaries
    • FF = GFR/RPF
    • The normal filtration fraction is ~20%

    Renal Clearance

    • Renal clearance is the rate at which a substance is removed/cleared from plasma
    • Complete volume of plasma that is cleared of a substance by the kidneys per unit time
    • C = [U]x x V / [P]x
      • C = clearance
      • [U]x: urine concentration of substance x
      • V= urine flow
      • [P]x: plasma concentration of substance x
    • The higher the renal clearance, the more plasma completely cleared of that substance

    Clearance Ratio

    • The clearance ratio for sodium, CRNa+ = CNa+/Cinulin
    • CNa+ = Renal clearance of sodium
    • Cinulin = Renal clearance of inulin
    • If CRNa+ < 1, then Na+ is reabsorbed
    • If CRNa+ > 1, then Na+ is secreted

    True/False Questions

    • Glomerular filtration is the last step in urine formation: False
    • Starling Forces modify GFR: True
    • GFR is indirectly proportional to NFP: True
    • Unfiltered proteins will ↑ the oncotic P of glomerular capillary blood: True
    • Filtration fraction = RPF / GFR: False
    • Inulin is a glomerular marker, as is creatinine: True
    • If Filtered load < excretion rate, we expect a substance is reabsorbed: True

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Lecture 25: Glomerular Filtration Rate & Renal Clearance - Fall 2024

    Description

    This quiz covers the fundamental concepts of glomerular filtration, focusing on the role of Starling forces in regulating glomerular filtration rate (GFR). It explains how changes in pressures and resistance in the afferent and efferent arterioles affect GFR. Test your understanding of these essential physiological principles.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser