53 Na+ and K+ homeostasis

Question 1

Passage of fluid through the tubules in the absence of ADH (lack of water reabsorption) leads to ___ urine

Answer 1

Diluted (aka hypotonic) urine

Question 2

T/F. In hypotonic urine the osmolarity is less than the plasma osmolarity (CH20<Posm

Answer 2

In hypotonic urine the osmolarity is less than the plasma osmolarity (CH20>0), Uosm<Posm

Question 3

Water is reabsorbed in the presence of ADH leads to ___ urine

Answer 3

Concentrated urine

Question 4

T/F. Uosm = Posm, therefore CH20= 0

Answer 4

True

Question 5

Increases water permeability in DT and collecting tubules

Answer 5

Aldosterone

Question 6

Inserts aquaporin channels into the membranes of the DT and collecting ducts, increasing water reabsorption
 Increases urea permeability by placing a urea channels in the membrane, important for gradient creation
 Stimulates Na+ transport in ascending loop, contributing to the gradient that water needs to move

Answer 6

ADH

Question 7

T/F. High osmolarity of the renal medulla and countercurrent flow of tubular fluid are required for the formation of concentrated urine

Answer 7

True

Question 8

This hormone is released from the posterior pituitary and increases water permeability in the collecting tubules and DT

Answer 8

ADH (aka vasopressin)

Question 9

detect changes in osmolarity and have the ability to stimulate neurons of the hypothalamus that can induce secretion of ADH from the posterior pituitary (into blood).

Answer 9

Osmoreceptors

Question 10

• Increased plasma osmolarity
• Decreased blood volume
• Decreased blood pressure
• Also, nausea, hypoxia, and certain drugs (morphine, nicotine)

Answer 10

Triggers hat stimulate secretion of ADH

Question 11

• Decreased plasma osmolarity
• Increased blood volume
• Increased blood pressure
• Alcohol (leads to dehydration)

Answer 11

Factors that inhibit ADH secretion

Question 12

binds to the g-protein coupled receptor V2. This increases cAMP production, which increases aquaporin-2 insertion in the membrane

Answer 12

ADH

Question 13

Failure to produce ADH (deficiency is in the brain –CNS)

Answer 13

Central diabetes insipidus

Question 14

Failure to respond to ADH (deficiency is in the kidneys –i.e. in receptors or in signaling). Salt reabsorption in the loop of henle is impaired. Can be caused by loop diuretics, lithium or analgesics, decreased urea concentration, and kidney disease

Answer 14

Nephrogenic diabetes insipidus

Question 15

In this type of nephron, the glomerulus is in the renal cortex and the tubules are short and mainly in the cortical area

Answer 15

Cortical nephron

Question 16

In this type of nephron, the glomerulus is in the junction b/t the cortex and the medulla, and the loops of henle are very big. These nephrons are responsible for establishing and maintaining the corticomedullary gradient

Answer 16

Juxtamedullary nephron

Question 17

This portion of what type of nephron functions as the countercurrent multiplier (creates a concentration gradient)

Answer 17

Loops of henle of the juxtamedullary nephrons

Question 18

This portion of what type of nephron functions as the countercurrent exchanger (diffusion occurs)

Answer 18

Vasa recta of the juxtamedullary nephrons

Question 19

(so named b/c the thin descending loop and the ascending loop do two different things) creates a hyperosmotic medullary interstitium

Answer 19

Countercurrent multiplier mechanism

Question 20

The blood vessels that surround the loop of henle. They ensure that the NaCl that is placed in the interstitial fluid doesn’t diffuse away. Instead it remains there and equilibrates. This is b/c the blood flow through these vessels is very slow, allowing for the time necessary for equilibration (if blood flow was rapid, all of the NaCl that is placed in the interstitium would be lost)

Answer 20

Vasa recta

Question 21

T/F. The countercurrent mechanism maintains the corticomedullary gradient (active process), while the vasa recta establishes the gradient (passive process

Answer 21

False. The countercurrent mechanism establishes the corticomedullary gradient (active process), while the vasa recta maintains the gradient (passive process)

Question 22

T/F. ADH promotes the insertion of urea channels in the distal collecting duct. Urea leaves and is deposited into the interstitial fluid

Answer 22

True

Question 23

T/F. Urea is freely filtered. About 20% is reabsorbed in the PT. After this point, urea is only reabsorbed in the distal collecting tubule

Answer 23

False. Urea is freely filtered. About 50% is reabsorbed in the PT. After this point, urea is only reabsorbed in the distal collecting tubule

Question 24

Produced from the ammonia that is produced from the breakdown of proteins

Answer 24

Urea

Question 25

T/F. The recirculation of urea helps to trap urea in the renal medulla and contributes to the hyperosmolarity of the renal cortex

Answer 25

False. The recirculation of urea helps to trap urea in the renal medulla and contributes to the hyperosmolarity of the renal medulla

Question 26

T/F. High protein degradation is a reason for a high BUN (blood urea nitrogen) value

Answer 26

True

Question 27

In the case of ECF volume contraction, which value increases more? Creatinine or BUN?

Answer 27

BUN increases more. BUN/creatinine > 20 is a marker for volume contraction

Question 28

These molecules collapse the gradient required for water absorption. They increase filtrate osmolarity by reabsorbing salt in a region in which water cannot follow. This increases water excretion due to increased osmosis

Answer 28

Diuretics. In general, diuretics allow for increased excretion of water

Question 29

T/F. The kidney regulates ECF osmolarity by regulating the amount of Na+ that is excreted. This is b/c Na+ is the major determinant of ECF osmolarity

Answer 29

False. The kidney controls ECF osmolarity by regulating the amount of water that is excreted: Water is the major determinant of ECF osmolarity (and ADH is the major determinant of water reabsorption)

Question 30

T/F. The physiological control in the PT affect the excretion of sodium and water together, whereas the actions of aldosterone and ADH in the distal nephron regulate sodium and water independently

Answer 30

True