Renal Physiology Quiz: Glomerular Filtration

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Questions and Answers

Which vessel has the highest percentage of total renal vascular resistance?

Afferent arteriole

Interlobar arteries

Efferent arteriole (correct)

Glomerular capillaries

What is the approximate pressure in the glomerular capillaries at the beginning of the vessel?

100 mm Hg

60 mm Hg (correct)

85 mm Hg

48 mm Hg

Which hormone or autacoid is known to increase GFR?

Endothelial-derived nitric oxide (correct)

Endothelin

Epinephrine

Norepinephrine

Which of the following statements regarding Angiotensin II's effect on GFR is true?

It prevents a decrease in GFR Signup and view all the answers

What role do the epithelial cells of the glomerular capillary wall play in filtration?

They restrict the filtration of plasma proteins. Signup and view all the answers

How does the thickness of the glomerular capillary membrane compare to other capillaries?

It is thicker but more porous. Signup and view all the answers

What percentage of renal plasma flow (RPF) does the glomerular filtration rate (GFR) typically represent?

20% Signup and view all the answers

Which statement correctly describes the filtration fraction in renal physiology?

It is GFR divided by renal plasma flow (RPF). Signup and view all the answers

What does a filterability of 1.0 indicate about a substance in renal filtration?

It is filtered as readily as water. Signup and view all the answers

What is a primary factor determining the filtering process in the glomerulus?

The size and electrical charge of molecules. Signup and view all the answers

Why is it significant that more than 99% of filtered fluid is reabsorbed during renal filtration?

It prevents dehydration and loss of vital nutrients. Signup and view all the answers

Which of the following factors can influence the filterability of solutes in the glomeruli?

Both size and electrical charge of the solutes. Signup and view all the answers

What is the average colloid osmotic pressure of glomerular capillary plasma proteins?

32 mm Hg Signup and view all the answers

How does increasing hydrostatic pressure in Bowman’s capsule affect glomerular filtration rate (GFR)?

Decreases GFR Signup and view all the answers

Which two main factors influence the glomerular capillary colloid osmotic pressure?

Fraction of plasma filtered and arterial plasma colloid osmotic pressure Signup and view all the answers

What can cause an increase in Bowman’s capsule pressure in pathological conditions?

Obstruction of the urinary tract Signup and view all the answers

What is the estimated Bowman’s capsule pressure in humans under normal conditions?

18 mm Hg Signup and view all the answers

What effect does decreasing Bowman’s capsule pressure have on glomerular filtration rate (GFR)?

Increases GFR Signup and view all the answers

How does increasing the fractional plasma filtered by the glomerular capillaries affect colloid osmotic pressure?

Increases the colloid osmotic pressure Signup and view all the answers

What is the primary way Bowman’s capsule pressure regulates GFR under normal conditions?

It does not serve as a primary means for regulating GFR. Signup and view all the answers

What is the myogenic mechanism primarily responsible for in renal physiology?

Regulating renal blood flow despite changes in arterial pressure Signup and view all the answers

What physiological response occurs when vascular wall tension increases?

Contraction of vascular smooth muscle cells Signup and view all the answers

How does the myogenic mechanism affect renal blood flow when arterial pressure rises?

It prevents excessive increases in renal blood flow and GFR Signup and view all the answers

What triggers the contraction of smooth muscle cells in response to vascular stretch?

Increased movement of calcium ions from extracellular fluid into the cells Signup and view all the answers

What is a consequence of the myogenic autoregulation when faced with high arterial pressures?

Increased vascular resistance leading to stable renal blood flow Signup and view all the answers

What happens to urine flow if tubular reabsorption remains constant at 178.5 L/day?

Urine flow increases to 46.5 L/day Signup and view all the answers

What is the significance of the total plasma volume being about 3 liters in relation to urine output?

A rapid change in urine output can lead to depletion of blood volume Signup and view all the answers

What is the primary function of renal autoregulation?

To maintain stable glomerular filtration rate (GFR) despite pressure fluctuations Signup and view all the answers

What phenomenon describes the adaptive mechanism in renal tubules when GFR rises?

Glomerulotubular balance Signup and view all the answers

What occurs to urine volume with large fluctuations in arterial pressure?

Urine volume remains unaffected by arterial changes Signup and view all the answers

How is the concept of glomerulotubular balance relevant to renal function?

It minimizes the impact of fluctuating GFR on urine output Signup and view all the answers

What is the relationship between GFR and tubular reabsorption in maintaining renal homeostasis?

Balanced GFR and tubular reabsorption are critical for urine volume regulation Signup and view all the answers

What would happen to blood volume if urine output increased by more than 30-fold?

Blood volume would quickly deplete Signup and view all the answers

What occurs when sodium chloride concentration decreases due to low renal perfusion pressure?

Increased renin release from juxtaglomerular cells Signup and view all the answers

What is a consequence of administering angiotensin II blocking drugs in patients with renal artery stenosis?

Severe decrease in GFR leading to renal failure Signup and view all the answers

Which of the following statements best describes the role of renin in response to decreased sodium chloride concentration?

It increases angiotensin I formation for vasoconstriction. Signup and view all the answers

What physiological effect does angiotensin II have on the efferent arterioles?

Constrains efferent arterioles to increase glomerular pressure Signup and view all the answers

What is one potential result of the interaction between decreased renal perfusion pressure and angiotensin-converting enzyme inhibitors?

Reduction of GFR beyond expected levels Signup and view all the answers

What two mechanisms are triggered by the macula densa in response to low sodium chloride concentration?

Decreased afferent arteriolar resistance and increased renin release Signup and view all the answers

How does angiotensin II contribute to the restoration of glomerular filtration rate (GFR)?

By constricting the efferent arterioles Signup and view all the answers

What is an important consideration when treating hypertension with angiotensin II receptor antagonists in patients with renal artery stenosis?

Careful monitoring is essential to avoid acute renal failure. Signup and view all the answers

Study Notes

Glomerular Filtration

The first step in urine formation involves filtration of large amounts of fluid through the glomerular capillaries into Bowman's capsule.
Approximately 180 liters of fluid are filtered daily.
Most of this filtrate is reabsorbed, leaving about 1 liter of fluid for excretion.
The high filtration rate is due to high kidney blood flow and specialized glomerular capillary properties.

Glomerular Filtrate Composition

The glomerular filtrate is essentially protein-free and devoid of cellular elements (like red blood cells).
Concentrations of other components, such as salts and organic molecules, are similar to plasma concentrations.
Exceptions include calcium and fatty acids, which are not freely filtered due to protein binding.

Glomerular Filtration Rate (GFR)

GFR is approximately 125 ml/min or 180 L/day in the average adult human.
This represents about 20% of the renal plasma flow.
The relationship between GFR and renal plasma flow is calculated as filtration fraction = GFR/Renal plasma flow.

Glomerular Capillary Membrane

The membrane is similar to other capillaries, but has three layers: endothelium, basement membrane, and podocytes.
This three-layered structure acts as a filtration barrier, enabling significant fluid and solute filtration while blocking plasma proteins.
High filtration rate is due to the presence of fenestrations (small holes) in the capillary endothelium and negatively charged molecules in the basement membrane and podocytes which hinder filtration of large negatively charged molecules.

Factors Determining GFR

The balance of hydrostatic and colloid osmotic pressures across the capillary membrane.
The capillary filtration coefficient (Kf), a product of permeability and filtering surface area.
The glomerular hydrostatic pressure and Kf contribute to higher filtration rate in glomerular capillaries when compared to other capillaries.

Determinants of GFR

Net filtration pressure: Sum of hydrostatic and colloid osmotic pressures.
Glomerular filtration coefficient (Kf): Permeability and surface area of glomerular capillaries.
Hydrostatic forces from both Glomerular hydrostatic pressure (PG), and Bowman's Capsule Hydrostatic pressure (PB).
Colloid osmotic forces from both Glomerular colloid osmotic pressure (π) and Bowman's capsule colloid osmotic pressure (πb).

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Description

Test your knowledge on renal physiology, specifically focusing on glomerular filtration and relevant mechanisms. This quiz covers key concepts like renal vascular resistance, GFR, and the factors affecting filtration. Ideal for students studying human physiology or nephrology.