Physiology: Glomerular Filtration Rate (GFR) Regulation
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Questions and Answers

What is the term for the ability of the kidneys to maintain a constant GFR despite changes in arterial pressure?

  • Glomerulotubular balance
  • Renal autoregulation (correct)
  • Myogenic mechanism
  • Pressure diuresis

    • What is the mechanism by which the renal tubules increase their reabsorption rate when GFR rises?

  • Myogenic mechanism
  • Glomerulotubular balance (correct)
  • Renal autoregulation
  • Pressure diuresis

    • What is the term for the response of small arterioles to increased wall tension or wall stretch?

  • Myogenic mechanism (correct)
  • Pressure diuresis
  • Glomerulotubular balance
  • Renal autoregulation

    • What is the purpose of the myogenic mechanism in the renal circulation?

    <p>To prevent excessive increases in renal blood flow and GFR</p> Signup and view all the answers

    What is the term for the increase in urine production in response to increased arterial pressure?

    <p>Pressure diuresis</p> Signup and view all the answers

    What is the composition of the glomerular filtrate?

    <p>Fluid with a similar composition to plasma, except for low molecular-weight substances</p> Signup and view all the answers

    Why are certain low molecular-weight substances not filtered in the glomerular filtrate?

    <p>Because they are bound to plasma proteins</p> Signup and view all the answers

    What is the purpose of the contraction of vascular smooth muscle in the myogenic mechanism?

    <p>To prevent excessive stretch of the vessel</p> Signup and view all the answers

    What is the primary function of autoregulation in the kidneys?

    <p>To maintain constant renal blood flow and GFR over a range of arterial pressures</p> Signup and view all the answers

    What is the main effect of a big activation of the renal sympathetic nerves on renal blood flow and GFR?

    <p>Decreases renal blood flow and GFR</p> Signup and view all the answers

    What is the role of endothelin in the kidneys?

    <p>It contributes to renal vasoconstriction and decreased GFR</p> Signup and view all the answers

    What is the effect of angiotensin II on renal blood flow and GFR?

    <p>Decreases renal blood flow and GFR</p> Signup and view all the answers

    What is the primary function of vasodilators like nitric oxide and prostaglandins in the kidneys?

    <p>To dilate the afferent arterioles and increase GFR</p> Signup and view all the answers

    What percentage of the kidney's blood flow goes to the renal cortex?

    <p>95%</p> Signup and view all the answers

    What is the effect of vasoconstriction hormones like NA and epinephrine on renal blood flow and GFR?

    <p>Decreases renal blood flow and GFR under extreme conditions</p> Signup and view all the answers

    What is the main mechanism by which the kidneys control renal blood flow and GFR?

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

    What is the effect of angiotensin II on the efferent arterioles?

    <p>Increases vasoconstriction</p> Signup and view all the answers

    Which autacoid is responsible for basal level production of vasodilation in the kidneys?

    <p>Endothelial-derived nitric oxide</p> Signup and view all the answers

    What is the effect of inhibiting nitric oxide formation on renal vascular resistance?

    <p>Increases renal vascular resistance</p> Signup and view all the answers

    What is the effect of prostaglandins on renal blood flow and GFR in illness?

    <p>Increases renal blood flow and GFR</p> Signup and view all the answers

    What is the purpose of autoregulation in the kidneys?

    <p>To control renal excretion of water and solutes</p> Signup and view all the answers

    What is the effect of bradykinin on renal blood flow?

    <p>Increases renal blood flow</p> Signup and view all the answers

    Study Notes

    Renal Blood Flow and Glomerular Filtration Rate (GFR)

    • Renal blood flow and GFR remain relatively constant despite changes in arterial pressure due to autoregulation.
    • GFR barely changes by 10% due to autoregulation and additional adaptive mechanisms in the renal tubules.

    Autoregulation of Renal Circulation

    • Renal auto regulation prevents large changes in GFR.
    • Additional adaptive mechanisms in the renal tubules, called glomerulotubular balance, increase reabsorption rate when GFR rises.

    Pressure Diuresis and Natriuresis

    • Changes in arterial pressure have significant effects on renal excretion of water and sodium, known as pressure diuresis or pressure natriuresis.
    • This is crucial in regulating body fluid volumes and arterial pressure.

    Myogenic Mechanism of Renal Circulation

    • Myogenic mechanism is the ability of blood vessels to resist stretching during increased arterial pressure.
    • It prevents excessive increases in renal blood flow and GFR when arterial pressure increases, protecting the kidney from hypertension-induced injury.

    Glomerular Filtrate

    • Urine formation begins with filtration of fluid through glomerular capillaries into Bowman's capsule.
    • Glomerular filtrate has almost no protein or cells, with concentrations similar to plasma, except for a few low molecular-weight substances.

    Renal Blood Flow Control

    • The kidneys have effective mechanisms for maintaining renal blood flow and GFR relatively constant over an arterial pressure range of 80-170 mm Hg.
    • Renal cortex receives more than 95% of the kidney's blood flow, with only 2% of blood flow in the renal medulla.
    • The GFR is determined by many variables, including glomerular hydrostatic pressure and glomerular capillary colloid osmotic pressure.

    Sympathetic Nervous System Control

    • All blood vessels of the kidneys are innervated by sympathetic nerve fibers.
    • A big activation of the renal sympathetic nerves constricts the renal arterioles and decreases renal blood flow and GFR.

    Hormonal and Autacoids Control of Renal Circulation

    • Vasoconstriction hormones (NA and epinephrine) only cause reductions in GFR and renal blood flow under extreme conditions, such as severe hemorrhage.
    • Endothelin, a peptide released by damaged vascular endothelial cells of the kidneys, contributes to homeostasis and renal vasoconstriction.
    • Angiotensin II is formed in the kidneys and in the systemic circulation, and there are receptors in all blood vessels of the kidneys, except the afferent arterioles.
    • Prostaglandins (PGE2 and PGI2) and bradykinin cause vasodilation and increased renal blood flow and GFR.
    • Endothelial-derived nitric oxide, an autacoid, decreases renal vascular resistance and maintains vasodilation of the kidneys.

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    Related Documents

    Unit 11.2 Renal Function PDF

    Description

    This quiz covers the regulation of glomerular filtration rate (GFR) and its maintenance despite changes in arterial pressure, including renal auto-regulation and glomerulotubular balance.

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