Block 4.1 -- Sodium and Water

Question 1

Kidneys regulate what (plasma) and plasma ions, ie, what is filtered?

Answer 1

Water

Question 2

The majority of reabsorption (~60%) occurs where?

Answer 2

Proximal tubule

Question 3

The second place where the most absorption occurs is where?

Answer 3

Loop of Henle

Question 4

Given the large amount of sodium filtered/absorbed, the reabsorption of sodium is critical for water reabsorption (what) and other solutes (what and what)?

Answer 4

Osmosis, glucose and chloride

Question 5

Is reabsorption regulated (obligate) or not regulated in the early nephron?

Answer 5

Not regulated

Question 6

Where is absorption regulated and by what?

Answer 6

Late distal tubule/collecting duct, being regulated by aldosterone

Question 7

In each compartment, are the number of cations more, less, or equal to the number of anions?

Answer 7

Equal to

Question 8

Is osmolality equal in all compartments?

Answer 8

Yes

Question 9

What is osmolality?

Answer 9

The number of solutes particles dissolved in solution (water)

Question 10

What two variables does osmolality reflect? Can they be independently regulated?

Answer 10

Water and solute, and yes they can

Question 11

What controls osmolality of body fluids?

Answer 11

Kidneys

Question 12

Kidneys control osmolality of body fluids by excreting either a concentrated or diluted urine. Which one has more solute and which has more water?

Answer 12

Diluted has more water and concentrated has more solute

Question 13

What is the major determinant of osmolality plasma, which has an inverse relationship?

Answer 13

Na+

Question 14

What in the hypothalamus detects increases in osmolality?

Answer 14

Osmoreceptors

Question 15

What triggers thirst and decreased excretion of water in urine?

Answer 15

Osmoreceptors

Question 16

Osmoreceptors are not stimulated when plasma osmolality is high or low?

Answer 16

Plasma osmolality is low

Question 17

The collecting duct is permeable to water but not permeable to what?

Answer 17

Na+

Question 18

Where is ADH produced and where is it released/stored?

Answer 18

ADH is produced in the hypothalamus but released and stored in the posterior pituitary gland

Question 19

Is ADH released in response to an increase or decrease in plasma osmolality?

Answer 19

Increase in plasma osmolality

Question 20

Is the secretion of ADH and effects on urine volume an inverse relationship or a direct relationship?

Answer 20

Inverse relationship

Question 21

What causes insertion of water pores into the apical membrane?

Answer 21

Vasopressin

Question 22

In the homeostasis of plasma Na+, when ADH decreases, does aldosterone increase or decrease?

Answer 22

Aldosterone increases

Question 23

What maintains a low intracellular concentration of Na+, establishing a concentration gradient that allows for the reabsorption of sodium via a number of different transporters?

Answer 23

Na+/K+ ATPase

Question 24

Where is the Na+/K+ ATPase in the proximal tubule?

Answer 24

Basolateral membrane

Question 25

The proximal tubule drives glucose reabsorption via what transporter? What type of transport is it?

Answer 25

SGLT, secondary active transport

Question 26

The proximal tubule conserves bicarbonate via the sodium hydrogen exchanger called what? What type of transport is it?

Answer 26

NHE, which is secondary active transport

Question 27

The proximal tubule conserving bicarbonate via the NHE is important in regulating what?

Answer 27

pH

Question 28

The ascending limb in the nephron absorbs what?

Answer 28

Na+K+2Cl-

Question 29

The descending limb in the nephron absorbs what?

Answer 29

Na+Cl-

Question 30

Aldosterone increases or decreases sodium reabsorption in the distal tubule/collecting duct (principal cells)?

Answer 30

Increases sodium reabsorption

Question 31

How does aldosterone increase sodium reabsorption?

Answer 31

ENaC (Epithelial sodium channels)

Question 32

A decrease in blood pressure increases or decreases Ang 2, aldosterone, and sodium reabsorption?

Answer 32

Increases

Question 33

Aldosterone only regulates what percentage of filtered sodium load, which amounts to 30 grams of NaCl daily?

Answer 33

2%

Question 34

A rise in blood K+ directly stimulates production of what in the adrenal cortex?

Answer 34

Aldosterone

Question 35

Does a fall in blood Na+ directly or indirectly stimulate aldosterone via the renin-angiotensin-aldosterone system?

Answer 35

Indirectly

Question 36

Does an increase in blood volume increase or decrease aldosterone production?

Answer 36

Decrease

Question 37

What part of the nephron is impermeable to water? Which part is paraceullular?

Answer 37

Ascending limb/distal tubule is impermeable, proximal tubule is paraceullular

Question 38

What part of the nephron is paracellular to chloride?

Answer 38

Proximal tubule

Question 39

Does chloride get reabsorbed via transporters or aquaporins? What about water?

Answer 39

Chloride -- Transporters Water -- Aquaporins

Question 40

Does an increase in blood volume increase or decrease release of atrial natridiuretic peptide hormone, which is from the atria of the heart when the walls are what?

Answer 40

Increases, stretched

Question 41

Atrial Natriuretic Peptide increases or decreases blood volume and blood pressure?

Answer 41

Decreases

Question 42

Atrial Natriuretic Peptide stimulates the kidneys to excrete more salt and therefore more water, leading to a decrease in what?

Answer 42

Aldosterone