L47: Regulation of Urine and the Creation & Role of the Medullary Osmotic Gradient

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57 Terms

1
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What kind of epithelium does the PCT have?

Cuboidal leaky microvilli

2
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What kind of epithelium does the DCT have?

Cuboidal tight

3
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What kind of epithelium does the nephron loop for the thin descending limb have?

Squamous tight

4
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What kind of epithelium does the nephron loop for the thick ascending limb have?

Cuboidal tight

5
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What kind of epithelium does the collecting duct have?

Cuboidal tight

6
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Only the … is squamous; it is the one part of the nephron that does not transport ions

thin limb

7
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What is the percentage of filtrate that the Loop of Henle is responsible for reabsorption?

25%

8
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What is the amount of water that the Loop of Henle is responsible for reabsorption?

45L per day

9
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What is the percentage of filtrate that the DCT and collecting reabsorbs?

5-14%

10
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What is the amount of water that the DCT and collecting reabsorbs?

9L per day

11
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Is the water (and solute) absorption in the Loop of Henle obligatory or facultative?

Obligatory

12
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Is the water (and solute) absorption in the DCT obligatory or facultative?

Facultative

13
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Where does each Loop of Henle descend into?

Hyperosmotic renal medulla

14
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What kind of nephron loop extends further into the medulla

Juxtamedullary nephron

15
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In the medulla there is an osmolarity gradient: … in the medulla = … osmolarity

deeper, higher

16
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Tubular fluid flows from the PCT to the … limb and on into the … limb

thin descending, thick ascending

17
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Counter-current: exchange occurs between fluids (in the limbs of the loop) moving in … directions

opposite

18
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Multiplication: exchange … as movement of fluid continues

increases

19
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The 2 limbs have different … for water and solute movement, which enhances overall reabsorption

permeabilities

20
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The blood vessels of the … also contribute to counter-current multiplication

vasa recta

21
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What phenomenon does the arrangement of the Loop of Henle create?

Counter-current multiplication

22
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The thin descending limb is … to water, but … to solutes

permeable, impermeable

23
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What water channel does thin limb cells express on their membrane?

Aquaporin-1

24
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Because the osmolarity of the ISF … as the limb goes deeper, the direction of tubular flow … water reabsorption

increases, enhances

25
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The thick ascending limb can … out of the tubular fluid but is … to water

pump ions, impermeable

26
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The thick limb can pump sodium and chloride out of the tubular lumen and into ISF due to expression of what transporter on the apical surface?

NKCC transporter

27
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What does NKCC stand for?

1 Na+ : 1 K+ : 2 Cl-

28
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Does osmolarity of tubular fluid increase or decrease in the thin descending limb?

Increase

29
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Does osmolarity of tubular fluid increase or decrease in the thick ascending limb?

Decrease

30
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What is the osmolarity gradient in the deep medulla partly maintained by?

Urea permeability

31
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Where are urea transporters (and thus permeability) only present in?

Papillary duct

32
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Where does the papillary duct run through?

Renal papilla

33
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The distal convoluted tubule and collecting duct are sites for … water and solute reabsorption

facultative

34
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Reabsorption will only occur in the DCT and collecting duct if stimulated by … signals

hormonal

35
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The epithelia in the DCT and collecting duct have little to no … transport and are … to water ‘at rest’

paracellular, impermeable

36
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Without hormone signalling: water would be … in the lumen of the DCT and CD even while passing through the high osmolarity in the deep medulla

retained

37
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Which hormones bind to DCT and CD cells allowing them to promote the addition of aquaporins to their apical membranes?

ADH/vasopressin

38
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Where is the anti-diurectic hormone (also called vasopressin or AVP) is secreted from?

Posterior pituitary

39
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AVPR activation signals for insertion of what?

Aquaporin-2

40
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What creates transmembrane permeability to water, allowing for osmotic reabsorption and concentration of urine?

Aquaporins

41
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What are aquaporins?

Water channels that allow water to rapidly diffuse according to the local osmotic gradient

42
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What are the body’s key effector for homeostatic regulation of body fluid osmolarity?

ADH levels

43
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ADH neurons in the hypothalamus are intrinsically …., so when plasma osmolarity increases, they produce higher frequencies of APs

osmosensitive

44
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What kind of feedback loop is the ADH regulation of plasma osmolarity?

Direct

45
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What endocrine disorder does the loss of either ADH secretion or AVPR2 lead to?

Diabetes insipidus (DI)

46
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Inherited diabetes insipidus can be caused by mutations in which genes?

AVP gene or AVPR2 gene

47
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Physical damage to what can prevent ADH secretion?

Hypothalamus or infundibulum of the pituitary

48
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… regulates … reabsorption and urine volume primarily through …

RAAS, ion, aldosterone

49
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Reductions in blood volume trigger the RAAS, resulting in … secretion

aldosterone

50
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What does aldosterone stimulate?

Sodium/potassium ion ATPase pump

51
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Aldosterone stimulate sodium/potassium ATPase pump, enhancing potassium ion … and sodium ion …

excretion, retention

52
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Which side of the membrane in the DCT does aldosterone stimulate sodium/potassium ion ATPase?

Basolateral

53
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In the DCT: aldosterone stimulates the sodium/potassium ion ATPase in the basolateral membrane, amplifying the gradient for sodium ion reabsorption at the … membrane

apical

54
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In the CD (principle cells): aldosterone causes addition of … channels (sodium leak channels) to the apical surface, enhancing sodium ion reabsorption

ENaC

55
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In response to a loss of volume, what does aldosterone (and ADH) both contribute to?

Homeostasis of fluid

56
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What is a diuretic?

Any drug that causes diuresis (increased production of urine)

57
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Most diuretics are … for specific renal transporter proteins, and they are often prescribed to manage hypertension or oedema

inhibitors