Renal Physiology Quiz M 3.2

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Questions and Answers

How does an increase in resistance in the interlobular arteries affect renal blood flow?

  • Increases renal blood flow
  • Increases GFR
  • Decreases renal blood flow (correct)
  • Has no effect on renal blood flow

What is the primary determinant of GFR?

  • Colloid osmotic pressure
  • Glomerular hydrostatic pressure (correct)
  • Renal vein hydrostatic pressure
  • Renal artery hydrostatic pressure

Which of the following hormones or drugs is known to directly influence Starling forces and GFR, as discussed in the content?

  • Antidiuretic hormone (ADH) (correct)
  • Growth hormone
  • Cortisol
  • Insulin

What is the primary factor determining the filtration of molecules through the glomerular filtration barrier?

<p>The size of the molecules (A), The electrical charge of the molecules (B)</p> Signup and view all the answers

What is the approximate size of the pores in the glomerular membrane?

<p>8 nanometers (D)</p> Signup and view all the answers

What is the role of the vasa recta in the renal medulla?

<p>Supplying blood to the medulla (D)</p> Signup and view all the answers

What is a potential cause for the increased permeability of the glomerular filtration barrier to plasma proteins?

<p>An abnormal T-cell response leading to cytokine secretion (C)</p> Signup and view all the answers

Which of the following statements is TRUE regarding sympathetic nervous system stimulation and renal blood flow?

<p>Strong stimulation constricts renal arterioles, decreasing renal blood flow. (A)</p> Signup and view all the answers

Which factor does NOT contribute to the net filtration pressure?

<p>Blood pressure in the afferent arteriole (A)</p> Signup and view all the answers

What is the relationship between resistance and renal blood flow?

<p>Increased resistance leads to decreased blood flow. (D)</p> Signup and view all the answers

Which of these factors directly affects the glomerular filtration rate (GFR)?

<p>All of the above (D)</p> Signup and view all the answers

What is the main factor responsible for the difference in blood flow between the renal cortex and medulla?

<p>Presence of the vasa recta in the medulla. (A)</p> Signup and view all the answers

Which of the following is NOT a major segment of the renal vasculature where resistance is controlled?

<p>Renal vein (B)</p> Signup and view all the answers

What is the typical range of the glomerular filtration coefficient (K_f) in a healthy individual?

<p>12.5 ml/min/mmHg (D)</p> Signup and view all the answers

How does increasing the hydrostatic pressure in Bowman's capsule affect the glomerular filtration rate?

<p>Decreases the GFR (D)</p> Signup and view all the answers

What is the primary mechanism for daily regulation of the glomerular filtration rate?

<p>Changes in the net filtration pressure (A)</p> Signup and view all the answers

What is the average filtration fraction?

<p>0.2 (C)</p> Signup and view all the answers

Which of the following forces contribute to the capillary filtration rate?

<p>Hydrostatic and colloid osmotic pressure (C)</p> Signup and view all the answers

How does the filtration fraction change when renal plasma flow decreases, assuming GFR remains constant?

<p>Increases (D)</p> Signup and view all the answers

Which of the following components of the filtration barrier is NOT negatively charged?

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

What is the main reason why proteins are not filtered through the glomerular capillaries?

<p>All of the above (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of the fenestrae found in the glomerular capillaries?

<p>They are negatively charged (B)</p> Signup and view all the answers

How much fluid is filtered daily from the glomerular capillaries into Bowman's capsule?

<p>180 liters (D)</p> Signup and view all the answers

What is the main reason why the capillary filtration rate is about 20% of renal plasma flow?

<p>All of the above (D)</p> Signup and view all the answers

What is the primary function of renal auto regulation?

<p>To regulate renal blood flow and GFR (B)</p> Signup and view all the answers

What would happen to GFR and urine output without auto regulation during a significant increase in blood pressure?

<p>GFR would increase dramatically while urine output would rise (B)</p> Signup and view all the answers

What is pressure diuresis?

<p>The increase in urine production due to rising blood pressure (D)</p> Signup and view all the answers

What change is observed in GFR as mean arterial pressure fluctuates between 50 and 200 mmHg?

<p>GFR remains relatively constant (B)</p> Signup and view all the answers

How does the renal system respond to increases in GFR?

<p>By increasing tubular reabsorption rates (A)</p> Signup and view all the answers

What primarily regulates the glomerular filtration rate (GFR) under normal physiological conditions?

<p>Hydrostatic pressure (D)</p> Signup and view all the answers

What is the typical daily GFR and how much of this is treated as urine under normal conditions?

<p>GFR is 180 L, with 1.5 L as urine (D)</p> Signup and view all the answers

How does an increase in colloid osmotic pressure generally affect GFR?

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

What role does cyclic GMP play in smooth muscle relaxation?

<p>It decreases calcium levels leading to relaxation (C)</p> Signup and view all the answers

Which statement about renal blood flow and GFR is true?

<p>Auto regulation keeps GFR relatively constant despite changes in arterial blood pressure (D)</p> Signup and view all the answers

What is the effect of increased renal plasma flow on colloid osmotic pressure?

<p>Decreases colloid osmotic pressure (D)</p> Signup and view all the answers

Which variable does NOT influence glomerular hydrostatic pressure?

<p>Volume of urine produced (A)</p> Signup and view all the answers

What occurs as a result of severe constriction of the efferent arterioles?

<p>Decreased GFR (B)</p> Signup and view all the answers

What happens to GFR when afferent arterioles experience increased resistance?

<p>GFR decreases (D)</p> Signup and view all the answers

What is the average colloid osmotic pressure in the capillaries after fluid removal for filtration?

<p>32 mm of mercury (D)</p> Signup and view all the answers

In what way does increasing arterial plasma colloid osmotic pressure affect filtration?

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

Which of the following hormones are responsible for constricting afferent and efferent arterioles, leading to a decrease in GFR and renal blood flow?

<p>Epinephrine and Norepinephrine (C)</p> Signup and view all the answers

What is the primary role of endothelin in the context of renal function?

<p>To constrict blood vessels, contributing to hemostasis in case of injury. (D)</p> Signup and view all the answers

Angiotensin II is a potent vasoconstrictor but its effect is not uniform throughout the renal vasculature. Which of the following vessels are particularly sensitive to angiotensin II?

<p>Efferent arterioles (C)</p> Signup and view all the answers

How does angiotensin II contribute to the maintenance of GFR despite reducing renal blood flow?

<p>By increasing glomerular hydrostatic pressure, promoting filtration. (D)</p> Signup and view all the answers

What is the role of nitric oxide in regulating renal blood flow?

<p>Dilating blood vessels, increasing renal blood flow and GFR. (C)</p> Signup and view all the answers

How do drugs that inhibit nitric oxide formation affect renal function?

<p>Increase renal vascular resistance and decrease GFR. (D)</p> Signup and view all the answers

Which of the following molecules is directly involved in the conversion of GTP to cyclic GMP, leading to vasodilation?

<p>Nitric oxide (B)</p> Signup and view all the answers

How does the interaction between nitric oxide and other drugs potentially affect the treatment of patients?

<p>It may increase the risk of side effects by triggering uncontrolled vasodilation. (A)</p> Signup and view all the answers

Flashcards

Glomerular Filtration Rate (GFR)

The rate at which blood is filtered through the glomeruli of the kidneys, averaging about 180L a day.

Filtration Fraction

The ratio of the glomerular filtration rate to renal plasma flow, average is about 0.2.

Renal Blood Flow

The volume of blood delivered to the kidneys per unit time, important for determining GFR.

Capillary Filtration Coefficient

A measure of the permeability of capillary membranes affecting filtration rate.

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Filtration Barrier Layers

Three layers: endothelium, basement membrane, epithelial cells that prevent large substances from passing.

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Colloid Osmotic Force

The pulling force exerted by proteins in plasma that affects fluid movement across capillary membranes.

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Hydrostatic Force

The physical force exerted by fluid within blood vessels that promotes filtration into the Bowman's capsule.

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Negative Charge in Capillaries

The negative electrical charges on cell proteins and basement membranes that hinder protein passage.

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Glomerular Filtration Barrier

A selective barrier in the kidneys filtering based on size and charge.

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Filtration Rate

The rate at which fluid is filtered through the glomeruli.

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Albumin Filtration

Albumin is minimally filtered due to its size and negative charge.

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Net Filtration Pressure

The balance of hydrostatic and osmotic pressures affecting filtration.

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Colloid Osmotic Pressure

The pressure exerted by proteins in blood plasma opposing filtration.

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Filtration Coefficient (CF)

A measure of the kidneys' filtering capacity, typically 12.5 ml/min.

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Hydrostatic Pressure Effects

Increased pressure in Bowman's capsule can reduce GFR.

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Proteinuria

The presence of excess proteins, particularly albumin, in urine.

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Increased Hydrostatic Pressure

Higher pressure within the glomerular capillaries, enhancing GFR.

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Afferent Arterial Resistance

The resistance blood encounters in the afferent arterioles, affecting GFR.

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Renal Plasma Flow

The volume of plasma that flows through the kidneys per time.

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Obstruction in Urinary Tract

Blockage that increases pressure in Bowman's capsule, reducing GFR.

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Effect of Arterial Constriction

Constriction affects GFR by altering hydrostatic and colloid osmotic pressures.

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Cyclic GMP

A signaling molecule that causes relaxation of smooth muscle and vasodilation.

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Autoregulation

The ability of the kidneys to maintain relatively constant GFR despite changes in blood pressure.

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Pressure Diuresis

Increased urine production due to elevated blood pressure, affecting body fluid regulation.

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Tubular Reabsorption

The process by which the kidneys reabsorb most of the filtered fluid back into the body.

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Effective Renal Plasma Flow

The volume of plasma that is effectively cleared by the kidneys per minute.

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Adaptive Mechanisms

Changes in the kidney tubules to manage reabsorption rates in response to GFR fluctuations.

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Norepinephrine and Epinephrine

Hormones that constrict afferent arterioles, reducing GFR and renal blood flow.

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Endothelium

Cells that line blood vessels, releasing substances that contribute to hemostasis.

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Angiotensin II

A hormone formed in the kidneys that constricts blood vessels and raises blood pressure.

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Vasodilators

Substances that counteract the effects of vasoconstrictors like angiotensin II, e.g., nitric oxide.

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Nitric Oxide

A gas produced in the body that decreases vascular resistance and promotes vasodilation.

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Glomerular Hydrostatic Pressure

Pressure within the glomerulus that facilitates filtration in the kidneys.

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Arginine's Role

Amino acid that stimulates the production of nitric oxide for vasodilation.

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Sympathetic Nervous System

Part of the autonomic nervous system that prepares the body for stress or emergencies.

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Renal Cortex

The outer portion of the kidney that receives most blood flow.

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Renal Medulla

The inner part of the kidney that receives only 1-2% of total renal blood flow.

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Hydrostatic Pressure

The pressure exerted by a fluid at rest, crucial for GFR regulation.

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Vasa Recta

The capillary network that supplies blood to the renal medulla.

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Study Notes

Renal Filtration, Blood Flow, and Control

  • Glomerular capillaries filter approximately 180 liters of fluid daily from the Bowman's capsule.
  • Most of this fluid is reabsorbed, leaving about one liter for excretion.
  • Filtration rate (GFR) varies based on fluid intake, kidney blood flow, and glomerular capillary membranes.
  • Capillaries are relatively impermeable to proteins and red blood cells but permeable to smaller molecules.
  • The capillary filtration rate is about 20% of renal plasma flow, influenced by the capillary filtration coefficient and the balance of hydrostatic and colloid osmotic forces. This ratio is about 0.2.

Capillary Membranes

  • Filtration barrier consists of three layers: endothelium, basement membrane, and epithelial cells.
  • Endothelium has perforations (fenestrations) allowing for rapid filtration.
  • Basement membrane has negative charges that hinder protein passage.
  • Epithelial cells (podocytes) have slit pores to further restrict protein filtration.
  • Negative charges in the membrane prevent the passage of proteins due to their similar charge.

Glomerular Filtration Barrier

  • Highly selective in determining which molecules are filtered.
  • Filters water readily.
  • Size and electrical charge determine filterability.
  • Larger molecules (like albumin) are filtered less due to their size and negative charge.

Light Chain Permeability

  • Factors like abnormal T-cell responses and cytokine secretion can cause permeability of plasma proteins (like albumin).
  • This can increase proteins in Bowman's capsule, leading to proteinuria (albuminuria).

Net Filtration Pressure

  • Determined by the sum of hydrostatic and colloid osmotic forces.
  • Components include: capillary hydrostatic pressure, Bowman's capsule hydrostatic pressure, capillary colloid osmotic pressure, and Bowman's capsule colloid osmotic pressure.
  • Colloid osmotic pressure in Bowman's capsule is generally negligible.

Regulation of GFR

  • Changes in glomerular hydrostatic pressure are a primary regulatory mechanism for GFR.
  • Increased hydrostatic pressure raises GFR.
  • Afferent arterial resistance is crucial; constriction decreases GFR by decreasing hydrostatic pressure, while dilation has the opposite effect.
  • Bowman's capsule pressure, too, impacts GFR. High pressure decreases GFR.
  • Other regulatory mechanisms and feedback mechanisms also maintain a relatively stable GFR, even with fluctuating arterial pressures.

Renal Blood Flow

  • The renal cortex receives a majority of the kidney's blood flow.
  • Autoregulation helps to maintain relatively constant blood flow despite variations in systemic blood pressure.
  • Factors like sympathetic nervous system activity, hormones, and local factors influence renal blood flow regulation.

Autoregulation and GFR

  • Autoregulation prevents major changes in GFR and renal excretion of water and solutes due to fluctuations in blood pressure.
  • GFR normally remains relatively constant between arterial pressures of 50 and 200mmHg. This helps maintain a constant rate of water and solute excretion.

Tubular Glomerular Feedback Mechanism

  • A special mechanism that links sodium chloride concentration changes in the macula densa with regulation of renal arterial resistance.
  • Helps maintain a constant delivery of sodium chloride to the distal tubule, and thereby prevents variations in renal excretion.

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