30 Questions
What is the term for the amount of a substance filtered per unit time?
Filtered Load
Which process involves the movement of substances from the peritubular capillary blood into the tubules?
Tubular Secretion
What is the term for the balance between the amount of fluid and solutes reabsorbed in the proximal tubule and the amount filtered by the glomerulus?
Glomerulotubular Balance
In which segment of the nephron is isosmotic reabsorption of NaCl observed?
Late Proximal Tubule
What is the term for the process by which substances are reabsorbed from the filtrate back into the bloodstream?
Reabsorption
What is the term for the rate at which a substance is excreted in the urine?
Urinary Excretion Rate
What is the primary function of transporters in the membranes of renal tubule epithelial cells?
Reabsorption and secretion of substances into the peritubular capillary blood
Which of the following substances is NOT reabsorbed from the glomerular filtrate into the peritubular capillary blood?
K+
What is the excretion rate of a substance equivalent to?
The amount of a substance excreted per unit time
What is the purpose of measuring the filtered load and excretion rate of a substance?
To determine whether a substance has been reabsorbed or secreted
What is the formula for calculating the filtered load of a substance?
GFR x [Px]
What can be inferred if a substance is present in the urine?
It may have entered the renal tubule by either filtration or secretion
Why would glucose molecules be excreted in the urine when the glucose concentration in the tubular fluid rises?
Because there are few remaining 'free' transporters to which they may re-attach
What is the significance of Tm in the context of renal handling of glucose?
It is the maximum amount of glucose that can be reabsorbed in the tubules
Why does glucosuria occur in uncontrolled diabetes mellitus?
Because the plasma glucose concentration exceeds Tm
What is the effect of pregnancy on the renal handling of glucose?
It increases the filtered load of glucose
What is the consequence of congenital abnormalities of the Na+ glucose cotransporter?
Decreased Tm
What is the formula to calculate the amount of a substance filtered per unit time?
GFR x filterable plasma concentration of the substance
What is the main characteristic of isosmotic reabsorption in the PT?
Solute and water reabsorption are coupled and proportional to each other
What is the primary function of the Na+-K+ ATPase in the PT?
To pump Na+ out of the cell and maintain isosmolarity
What is the effect of increased filtered load on reabsorption in the PT?
No change in reabsorption of isosmotic fluid
What is the primary mechanism of glomerulotubular balance in the PT?
Balance between filtration and reabsorption
What is the primary function of Starling's forces in the peritubular capillary?
To favor reabsorption of isosmotic fluid
What is the percentage of the filtered load that is reabsorbed by the PT?
67%
What is the primary function of the early distal tubule in terms of sodium reabsorption?
Reabsorption of sodium ions in an electro-neutral manner
What is the effect of thiazide diuretics on the Na+-Cl- cotransporter in the early distal tubule?
They inhibit the transporter, causing a decrease in sodium reabsorption
What is the primary function of principal cells in the late distal tubule and collecting duct?
Reabsorption of sodium ions and secretion of potassium ions
What is the mechanism of sodium reabsorption in the late distal tubule and collecting duct?
Sodium ions diffuse through Na+ channels on the luminal membrane and are then pumped out of the cell by Na+-K+-ATPase
What is the effect of aldosterone on sodium reabsorption in the late distal tubule and collecting duct?
It stimulates sodium reabsorption in the principal cells
What is the effect of K+-sparing diuretics on sodium reabsorption in the late distal tubule and collecting duct?
They inhibit sodium reabsorption in the principal cells
Understand the process of isosmotic reabsorption in the proximal tubule, including the characteristics of solute and water reabsorption. Learn about the major and minor ions involved and the routes of reabsorption.
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