Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Y2S2-RENAL/REPRO-PHYSIOLOGY > Tubular reabsorption > Flashcards

Tubular reabsorption Flashcards

1
Q

What are the molecules that are reabsorbed by the tubules?

A

1) Water

2) Sodium

3) Potassium

4) Chloride

5) Glucose

6) Amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the molecules that are secreted by the tubules?

A

1) Endogenous substances

2) Some drugs

3) Hydrogen Ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the factors that affects the glomerular reabsorption of glucose?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How is the potassium kept in balance?

A
  • In the ECF, potassium concentration is 4.2mEq/L (2% of K+), in the ICF (INTRACELLULAR FLUID), the potassium level is 140 mEq/L (98% of K+)
  • Internal potassium balance is difficult to maintain, however, the external balance of potassium is maintained by the rapid adjustment to excretion through the kidneys
  • Maintaining a precise volume of potassium is essential as an increase of 3-4 mEq/L can cause arrhythmias, and if higher, it can lead to cardiac arrest/fibrillation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is the external balance of potassium regulated?

A

By the adjustment of excretion through the kidneys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the agents that increase the uptake of potassium?

A

1) Insulin (most important)

2) Aldosterone

3) B-adrenergic stimulation

4) Acidosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the agents that increase the secretion of potassium from the ICF?

A

1) Insulin deficiency (in Diabetes mellitus)

2) Aldosterone deficiency (in addison, we will have low aldosterone and thus hyperkalemia)

3) B-adrenergic blockers

4) Metabolic Acidosis (leads to the loss of K+ from the cell)

5) Cell lysis

6) Strenuous exercise

7) Hyperosmolarity (inside the cell, the K+ concentration will be high as a result, and the cell will start to release its potassium)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the regulatory mechanism of the external potassium balance

A
  • The regulation of the excretion of potassium is controlled by the changes in potassium secretion in the distal tubule and collecting ducts
  • The kidney filters 180L of blood per day, given that the conc of potassium in the blood is 4.2mEq/L then the kidney filters 756mEq/ of potassium per day (the filter load of potassium)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What will happen to the secretion of potassium in regards to its intake?

A

1) High potassium intake:

  • Increased secretion of potassium

2) Low potassium intake:

  • Increased absorption and decreased secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

In which part of the nephron does the day-to-day regulation of potassium excretion occur?

A

1) Late distal tubule

2) Collecting tubules

  • They contain intercalated cells, which are very important for the secretion and reabsorption of potassium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where does the reabsorption of potassium occur?

A

1) PCT (65%)

2) Thick ascending limb of loop of Henle (27%), Na+, K+, and 2Cl- channels are found for the regulation of potassium

3) Collecting tubule (4%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What channels are found in the thick ascending loop of Henle that help regulate K+?

A

-Na+ - K+ - 2Cl- channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What controls the secretion of potassium?

A
  • Potassium secretion occurs in the principal cells

1) Activity of the Na-K+ ATPase pump

2) The electrochemical gradient

  • If there was a high conc of intracellular K+, it will then get secreted into the lumen via BK and ROMK channels

3) Permeability of the luminal membrane (-50mV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the physiological mechanism behind the secretion of potassium?

A

1) Using a sodium potassium pump the principal cells can release sodium into the blood for exchange with potassium using ATP

2) Aldosterone will also stimulate the release of potassium from the principal cells via the Na-K ATPase pump and by increasing the expression of the potassium channels (BK, ROMK channels) on the luminal membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What will happen to the secretion of potassium in chronic acidosis?

A

Reabsorption of sodium and water at the PCT is distorted = More sodium and water lost = Urine flow rate increases = inc excretion of potassium = Hypokalemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the role of Type-A intercalated cells in potassium homeostasis?

A
  • Intercalated cells which reabsorbs potassium, functioning in hypokalemia
  • They reabsorb potassium via the H+/K+ ATPase transporter to prevent hypokalemia, and the H+ secreted decreases acidosis
  • Potassium will then diffuse through the basolateral membrane and into the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the role of type b intercalated cells in potassium homeostasis?

A
  • They secrete potassium, functioning in hyperkalemia

1) H+/K+ ATPase transporter on the basolateral membrane will pump potassium in, then K+ will diffuse into the lumen through the potassium channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do the principal cells mainly regulate potassium levels?

A

1) Urine flow rate

2) Aldosterone

3) Diet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the things that increase the secretion of potassium?

A

1) Diet high in potassium

2) Increase in aldosterone

3) Alkalosis

4) Diuretic (increased urine flow = increased secretion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the factors that decrease the secretion of potassium?

A

1) Diet low in potassium

2) Decreased aldosterone

3) Acidosis

4) Potassium sparing diuretics

21
Q

In which part of the nephron is glucose reabsorbed?

A

The cells of the proximal convoluted tubule

  • Normally, there is no glucose in urine
22
Q

What are the mechanisms of glucose reabsorption?

A

1) Secondary active transport on the luminal side (SGLT1 & 2 “Na+/Glucose cotransporter)

  • 90% of glucose is reabsorbed by SGLT2 in the early part of the PCT
  • 10% of glucose is reabsorbed by the SGLT1 at a later segment of the PCT

2) Fascilitated diffusion on the basolateral side

  • GLUT2 (in the first part of the PCT, and GLUT1 at the distal part of the PCT) will transfer the intracellular glucose to the blood
23
Q

What is meant by filter load?

A

The quantity of a substance that is filtered per unit time

  • GFR * Solute plasma concentration
  • The high the plasma concentration the higher the filter load
24
Q

What is meant by the transport maximum?

A

The ability of the nephrons to reabsorb a substance

25
What is meant by the maximum tubular reabsorptive capacity?
The maximum amount of substance that can be absorbed per unit time
26
What is meant by the threshold?
When the plasma concentration of a substance starts appearing in urine
27
What is the threshold of glucose?
200 mg/dL, after which glucose starts appearing in urin,e especially when it increases beyond the maximum tubular reabsorption (375mg/dL)
28
Describe the glucose titration curve and transport maximum (Tm)
- Normally, all of the glucose filtered is reabsorbed - At a plasma concentration of 200 mg/dL all of the filtered load of glucose is reabsorbed; above 200 mg/dL the curve starts bending; above 350 gm/dL, all of the glucose carriers are saturated, and a pletau/transport maximum is reached - The maximum tubular reabsorptive capacity of glucose is 375 mg/min
29
What is the relationship between diabetes mellitus and glycosuria?
In uncontrolled diabetes mellitus, glucose levels become high, causing the filtered load of glucose to exceed the maximum transport excretion of glucose
30
Describe the process of urea filtration
1) Water is reabsorbed along the nephron, increasing the urea concentration in the tubular fluid and creating a driving force for the reabsorption of urea 2) In the PCT, 50% of the filtered urea is reabsorbed 3) In the thin descending limb of the loop of Henle, urea is secreted into the tubule due to the higher concentration of urea in the interstitium 4) At the inner medullary collecting duct, all of the urea is passively reabsorbed by the urea transporters (UT1)
31
What is the effect of ADH on the reabsorption of Urea?
ADH will increase the reabsorption of water at the distal tubule, increasing the concentration of urea, and thus urea reabsorption will increase
32
Describe the process of PAH (para-aminohippuric acid) filtration
- At low concentrations of plasma PAH, excretion is the filtration plus the secretion - At high concentrations, a pletau of PAH secretion is reached as the transporters get saturated
33
How is the phosphate handled in the nephron?
- 85% of phosphate is reabsorbed (70% by the PCT, and 15% by the DCT), and 15% is excreted - Phosphate is reabsorbed by the means of: 1) In the PCT, 70% of phosphate is reabsorbed via the Na+/Phosphate cotransporter (NaPi) - Phosphate reabsorption follows the maximum transport mechanism (Tm) like glucose where if the phosphate was = or < than 0.1 mmol/L, all of the phosphate will be reabsorbed - PTH inhibits the cotransporter (sodium/phosphate), decreasing the maximum transport of phosphate - Phosphate reabsorption occurs transcellularly (enters the cell via a tansporter and transports through the cell)
34
What is the effect of the parathyroid hormone on phosphate?
The PTH increases the phosphate secretion in urine (by inhibiting the sodium/phosphate cotransporter)
35
Where is the phosphate secreted into the tubule?
In the PCT and the DCT
36
Describe the reabsorption of calcium
- 99% of the calcium in our body is found in the bones, given that only the free form of calcium is ultrafilterable - Of the filtered calcium, 99% is reabsorbed (67% at the PCT, 25% at the thick ascending loop, and 8% at the DCT) - 80% of the reabsorbed calcium is done so paracellularly (dissolved in water), however, the other 20% is reabsorbed transcellularly via diffusion through the luminal membrane, and exits from the basolateral side via the calcium-ATPase pump & by the sodium/calcium counter-transporter
37
How is magnesium handled in the nephron?
- 95% of magnesium is reabsorbed and 5% is excreted - The primary site of magnesium reabsorption is the loop of Henle (60%) - 30% at the PCT - 60% At the loop of Henle - 5% at the DCT
38
What is the effect of loop diuretics like (furosemide) on the reabsorption of calcium and magnesium?
THEY INHIBIT THEIR REABSORPTION AND INCREASES THEIR EXCRETION
39
How is bicarbonate reabsorbed?
- 90/95% of bicarbonate is reabsorbed in the PCT, via the carbonic anhydrase mechanism
40
Describe the process of bicarbonate reabsorption
1) Na+/H+, sodium gets into the cell and the hydrogen out of the cell 2) Hydrogen will join with the HCO3- converting it to H2CO3 3) H2CO3- will get converted to CO2 and H2O 4) The CO2 and H2O will enter the cell and get converted back to HCO3- which will then exit the cell into the blood via either: 1) Na+/HCO3- cotransporter 2) HCO3-/Cl- cotransporter
41
What will happen if we inhibit the carbonic anhydrase?
1) Na+/H+ exchanger is inhibited 2) The reabsorption of bicarbonate decreases, resulting in acidosis 3) More water and sodium is lost in urine
42
How does the body respond to dehydration?
- In dehydration: 1) Plasma osmolarity will increase 2) Stimulation of the osmoreceptors in the hypothalamus 3a) Increased sensation of thirst, which will lead to drinking and decreasing the osmolarioty of the plasma 3b) Increased ADH secretion from the posterior pituitary 4) Increased water permeability in the principal cells (DCT and the collecting ducts 5) Increased water reabsorption 6) Increased urine osmolarity and decreased volume returning the plasma osmolarity towards normal
43
What happens to our body when we drink plenty of water?
1) Decreased plasma osmolarity 2) Inhibition of the receptors in the anterior hypothalamus 3a) decreased thirst and thus water intake, increasing the plasma osmolarity 3b) Decreased secretion of ADH 4) Decreased water permeability in the DCT and the collecting ducts 5) Decreased water reabsorption 6) Decreased urine osmolarity and increased volume, returning the plasma osmolarity towards normal
44
What are the different solutes that are absorbed at the nephron?
1) Amino acid 2) Protein 3) Glucose 4) HCO3 5) Potassium 6) Sodium 7) Chloride 8) Inulin 9) Urea 10) Creatinine 11) PAH
45
What are the substances that are slightly reabsorbed by the tubules and excreted in large quantities?
1) Urea 2) Inulin 3) Creatinine 4) PAH
46
What are the substances that are 100% reabsorbed?
1) Glucose 2) Amino acids
47
In which segment of the nephron is the glucose and amino acids reabsorbed?
Proximal convoluted tubule
48
In which segment of the nephron are the Na+, K+, and Cl-?
Loop of Henle (thick ascending)

Y2S2-RENAL/REPRO-PHYSIOLOGY (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions