Kidney Pt. 3

Question 1

What solutes are secreted during tubular secretion?

Answer 1

1. Creatinine.
2. Drugs (ex: Penicillin).
3. H+.
4. K+.
5. NH4+.

Question 2

What are the 2 important outcomes of tubular secretion?

Answer 2

1. Eliminate substances from the body.
2. Secretion of H+ to control body pH.

Question 3

What is reabsorption between adjacent tubule cells?

Answer 3

Paracellular reabsorption.

Question 4

What is reabsorption through an individual tubule cell?

Answer 4

Transcellular reabsorption.

Question 5

What is the concentration of Na+ ions in cells lining renal tubules?

Answer 5

Low concentration of Na+ ions, due to Na+/K+ ATPase pumps.

Question 6

Where are Na+/K+ ATPase pumps located in cells that line the renal tubules?

Answer 6

On the basolateral membrane.

Question 7

What does solute reabsorption drive?

Answer 7

Water reabsorption via osmosis.
*Obligatory.

Question 8

Where does water reabsorption occur?

Answer 8

PCT and descending LOH.

Question 9

What is the other method by which water is reabsorbed?

Answer 9

ADH acting on the kidney in the collecting duct.

Question 10

How is Na+ transported during reabsorption?

Answer 10

1. Symport.
2. Antiport.

Question 11

Where are Na+ symports located?

Answer 11

The apical membrane in the first half of the PCT.

Question 12

What is an example of a Na+ symport?

Answer 12

The Na+-glucose symporter.

Question 13

How does a Na+-glucose symport function?

Answer 13

2 Na+ and 1 glucose attach to the symporter protein and both move from the tubule fluid to the tubule cell.

Question 14

What layer does glucose exit at?

Answer 14

The basolateral membrane via facilitated diffusion.

Question 15

What is an example of an antiport?

Answer 15

The Na+/H+ antiport.

Question 16

How does the the Na+/H+ antiport work?

Answer 16

Filtered Na+ moves down the concentration gradient into PCT cells, while H+ moves from the cytosol into the lumen. Na+ is reabsorbed and H+ is secreted into tubular fluid.

Question 17

How is H+ produced in the PCT cells?

Answer 17

1. Metabolic reactions.
2. Peritubular blood.
3. Tubular fluid.

Question 18

What is the function of the enzyme carbonic anhydrase?

Answer 18

To catalyze the reaction of CO2 w/ H2O to form carbonic acid (H2CO3).

Question 19

What does carbonic acid dissociate into?

Answer 19

1. H+.
2. HCO3-.

Question 20

What % of filtered bicarbonate ions are reabsorbed?

Answer 20

80-90%.

Question 21

What occurs after H+ is secreted into the tubular fluid?

Answer 21

1. It reacts with HCO3- to form H2CO3.
2. H2CO3 dissociates into CO2 and H2O.
3. CO2 diffuses into tubule cells, joining with H2O to form H2CO3.
4. H2CO3 dissociates into H+ and HCO3-.

Question 22

What is reabsorbed for every H+ secreted into tubular fluid of the PCT?

Answer 22

1 HCO3- and 1 Na+.

Question 23

What occurs as water leaves the tubular fluid?

Answer 23

The concentration of remaining filtered solutes increases.

Question 24

What solutes passively diffuse in the second half of the PCT?

Answer 24

1. Cl- (In the highest amount).
2. K+.
3. Ca2+.
4. Mg2+.
5. Urea.

Question 25

What does the entrance of Cl- into the interstitial fluid promote?

Answer 25

Positive paracellular reabsorption of cations as a result of the interstitial fluid becoming more negative.

Question 26

Where are ammonia products derived from?

Answer 26

The deamination of amino acids.

Question 26

What do the cells lining the PCT and the descending LOH contain?

Answer 26

Aquaporin-1 molecules, plasma membrane proteins that are water channels.

Question 27

What organ converts most ammonia into urea?

Answer 27

The liver.

Question 28

Where is urea and ammonia filtered in the nephron? Secreted?

Answer 28

1. The glomerulus. 2. The PCT.

Question 29

What % of water is absorbed in the renal tubules is done so in the PCT?

Answer 29

~65%.

Question 30

How fast does fluid enter the LOH?

Answer 30

40 mL/min.

Question 31

What is the osmolarity of tubular fluid similar to in the LOH?

Answer 31

Blood.

Question 32

What does the LOH set the stage for?

Answer 32

The independent regulation of volume and osmolarity of body fluids.

Question 33

What symporters are found in the apical membrane of the thick ascending LOH?

Answer 33

Cl- (2), K+(1), Na+(1) symporters.

Question 34

Where is the Na+ transported to when reclaimed from the LOH?

Answer 34

Into the interstitial fluid and then into capillaries.

Question 35

Where is the Cl- transported to when reclaimed from the LOH?

Answer 35

Through leak channels in the basolateral membrane and then diffuses into capillaries.

Question 36

Where is the K+ transported to when reclaimed from the LOH?

Answer 36

Moves down a concentration gradient back into tubular fluid through leak channels.

Question 37

What is the main effect of Cl-, K+, Na+ symporters?

Answer 37

The reabsorption of Cl- and Na+.

Question 38

What happens as a result of K+ moving into the tubular fluid?

Answer 38

The interstitial fluid and blood become negative relative to the fluid in the ascending LOH, promoting paracellular cation reabsorption.

Question 39

What % of water is reabsorbed in the descending LOH? Ascending?

Answer 39

1. 15%. 2. Little to none, due to being impermeable to water.

Question 40

What happens to the osmolarity of tubular fluid as it approaches the end of the ascending limb?

Answer 40

It decreases.

Question 41

What is the rate of fluid flow when it enters the DCT?

Answer 41

25mL/min.

Question 42

What is reabsorbed in the DCT?

Answer 42

Na+ and Cl- by Na+-Cl- symporters in the apical membrane.

Question 43

What permits the reabsorption of Na+ and Cl- from the apical membrane into the peritubular capillaries?

Answer 43

1. Cl- leak channels. 2. Na+/K+ pumps. *Both located in the basolateral membrane.

Question 44

What does PTH stimulation of the DCT cause reabsorption of?

Answer 44

Ca2+.

Question 45

What % of water is reabsorbed in the DCT?

Answer 45

10-15%.

Question 46

What % of filtered solutes and water have been reabsorbed by the end of the DCT?

Answer 46

90-95%.

Question 47

What 2 types of cells are found lining the end of the DCT through the CD?

Answer 47

1. Intercalated. 2. Principal.

Question 48

What do intercalated cells allow for the reabsorption of? Secretion of?

Answer 48

1. HCO3- and K+. 2. H+.

Question 49

What do principal cells allow for the reabsorption of? Secretion of?

Answer 49

1. Na+. 2. K+.

Question 50

How does Na+ move through the apical membrane of principal cells?

Answer 50

Leak channels.

Question 51

What is the concentration of Na+ in the cytosol near the collecting duct?

Answer 51

Low, due to Na+/K+ pumps in the basolateral membrane. From here Na+ diffuses passively into the capillaries.

Question 52

How is most K+ returned to the bloodstream?

Answer 52

Reabsorption in PCT and LOH.

Question 53

What occurs when intracellular K+ remains high?

Answer 53

Na+/K+ pumps in the basolateral membrane activate. Some diffuses into tubular fluid via a concentration gradient.

Question 54

What 4 hormones affect Cl-, Na+, and water reabsorption and K+ secretion?

Answer 54

1. Angiotensin II. 2. Anti-Diuretic Hormone (ADH). 3. Aldosterone. 4. Atrial Natriuretic Peptide (ANP).

Question 55

What is the function of angiotensin II?

Answer 55

Regulator of electrolyte/ion reabsorption and secretion.

Question 56

What is the function of ADH?

Answer 56

Regulates water reabsorption.

Question 57

What is the function of aldosterone?

Answer 57

Regulator of electrolyte/ion reabsorption and secretion.

Question 58

What is the function of ANP?

Answer 58

Inhibiting electrolyte/ion and water reabsorption.

Question 59

What activates the renin-angiotensin-aldosterone system?

Answer 59

Decreased blood volume and decreased blood pressure leading to decreased stretching of the walls of the afferent arterioles.

Question 60

What cells secrete renin into the blood?

Answer 60

Juxtaglomerular cells in response to the decreased stretching of the afferent arterioles.

Question 61

What does renin act on and how?

Answer 61

Angiotensinogen by removing the 10 AAs called angiotensin I.

Question 62

What converts angiotensin I into its active form, angiotensin II?

Answer 62

Angiotensin converting enzyme (ACE).

Question 63

Where is angiotensinogen synthesized?

Answer 63

The liver.

Question 64

Where is angiotensin converting enzyme synthesized?

Answer 64

Lung tissue.

Question 65

In what 3 ways does angiotensin II impact the kidney?

Answer 65

1. Decrease in GFR due to vasoconstriction of afferent arterioles. 2. Enhancement of Cl-, Na+, and water reabsorption in the PCT by stimulating Na+/H+ antiporter activity. 3. Stimulates the adrenal cortex to secrete aldosterone, which causes increased reabsorption of Cl- and Na+ and secretion of more K+ by principal cells in the collecting ducts. *Ultimately, less water is excreted and blood volume increases as a result.

Question 66

What is the alternate name for ADH?

Answer 66

Vasopressin.

Question 67

Where is ADH released from?

Answer 67

The posterior pituitary gland.

Question 68

What type of water reabsorption does ADH regulate?

Answer 68

Facultative.

Question 69

What cells does vasopressin target?

Answer 69

Principal cells in the last part of the DCT and through the collecting duct. Leads to the opening of aquaporin-2 vesicles in the apical membrane.

Question 70

What occurs in the last part of the DCT and through the collecting duct in the absence of ADH?

Answer 70

There is low water permeability of the principal cells and the aquaporin-2 vesicles in the apical membrane retract.

Question 71

What do the aquaporin-2 vesicles allow for?

Answer 71

The flow of water from the lumen into the apical membrane, then into the bloodstream.

Question 72

What happens to urine output when ADH concentration is maximized?

Answer 72

The kidneys produce 400-500 mL of urine per day, very concentrated urine.

Question 73

What happens to urine output when ADH concentration is maximized?

Answer 73

The kidneys produce a large amount of very dilute urine.

Question 74

What type of feedback loop regulates the facultative reabsorption of water?

Answer 74

Negative feedback loop.

Question 75

What occurs as the osmolarity of the plasma and interstitial fluid increases?

Answer 75

Water concentration decreases, triggering the hypothalamic osmoreceptors to stimulate the PPG to release ADH, and ADH stimulates the principal cells to become more permeable to water, leading to a drop in plasma osmolarity.

Question 76

What are the functions of atrial natriuretic peptide?

Answer 76

1. Vasodilation. 2. Can inhibit Na+ and water reabsorption in the PCT and collecting duct. 3. Suppresses ADH and aldosterone secretion.

Question 77

What does the 3 functions of ANP lead to?

Answer 77

1. Increased natriuresis (Na+ output in the urine). 2. Diuresis. 3. Decreased blood volume and pressure.