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Unit 7: Physiology > the infamous Loop of Henle > Flashcards

the infamous Loop of Henle Flashcards

1
Q

Which segments are impermeable to water?

A

thin and thick ascending limb

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2
Q

What specifically is the driving force for the counter current multiplication system?

A

active reabsorption of NaCl in the thick ascending limb

  • reabsorption of 25% of filtered Na
  • mantains interstitium concentration gradient that inc from cortex to medulla
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3
Q

When plasma is hypoosmotic, what is the nature of the urine?

A

dilute

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4
Q

when plasma is hyperosmotic or contracted, what is the nature of the urine?

A

concentrated

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5
Q

ADH has what function in the nephron?

A

During INC plasma osmolarity:

  • inc water permeability of the collecting duct
  • inserts aquaporins into luminal and basolateral membranes
  • drives water reabsorption in excess of solute reabsorption
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6
Q

When ADH is present, what is the nature of the urine?

A

concentrated stinky urine because you are one dehydrated prune

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7
Q

How does the osmolarity of the tubular fluid in the diluting segment (tALH, tAL, DCT) change when a person is dehydrated?

A

it DOESN’T
osmolarity is always less than plasma
no matter if ADH is present or not - insensitive

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8
Q

How does the gradient in the interstitium change during diuresis?

A

gradient is still present, but is less steep

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9
Q

In the thin descending limb describe:

  1. permeability to solute
  2. permeability to water
  3. what happens to tubular fluid
A
  1. permeability to solute - low
  2. permeability to water - high
  3. what happens to tubular fluid - concentrated
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10
Q

In the thin ascending limb describe:

  1. permeability to solute
  2. permeability to water
A
  1. permeability to solute - high to NaCl and urea passively

2. permeability to water - impermeable

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11
Q

In the thick ascending limb describe:

  1. method of solute reabsorption
  2. water permeability
  3. what gradient it mantains
A
  1. active - Na/K/2Cl symporter
  2. impermeable
  3. 200 mOsm/L
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12
Q

What percent of filtered sodium and potassium is reabsorbed in medullary and cortical thick ascending limb?

A

25% of sodium

20% of potassium

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13
Q

What do loop diuretics inhibit?

A

Na/K/2Cl symporter in luminal membrane of thick ascending limb

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14
Q

How do ions move across the basolateral thick ascending limb?

A

NaKATPase and ion specific channels for Cl and K+

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15
Q

What creates the lumenal positive voltage potential?

A

K+ efflux in lumen, Cl- efflux in basolateral membrane

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16
Q

What is the positive voltage potential in the thick ascending limb a driving force for?

A

paracellular Na reabsorption

17
Q

What are the two basic steps of the countercurrent exchange mechanism?

A
  1. pumping of solute out ascending limb –> interstitium
  2. axial advance of fluid forward along tubule

pump- equilibrate - shift - equilibrate

18
Q

How would the gradient in the interstitium be affected if the loop of henle was longer?

A

the gradient would be increased

19
Q

the osmolarity of the inner medulla varies btwn what values in antidiuresis and diuresis?

A

antidiuresis - 1200 mOsm/L

diuresis - 500 mOsm/L

20
Q

How does the concentration of urea vary btwn antidiuresis and diuresis?

A

antidiuresis – 600 mM

diuresis - <100 mM (usually at around 0)

21
Q

In the outer medulla, the osmolarity of the interstitium is due mostly to what solute?

A

NaCl

22
Q

In the inner medulla the osmolarity is due to what solute?

A

50% Nacl and 50% urea

23
Q

What are the three steps of urea recycling?

A
  1. reabsorption at collecting duct
  2. secretion from medulla –> tDLH and tALH
  3. delivery of urea from tubular fluid to collecting duct
24
Q

what are two factors of the vasa recta that allow it to mantain the countercurrent exchange process?

A
  1. slower rate of blood flow

2. hairpin anatomy

25
Q

Is the diffusion of water and solutes through the vasa recta active or passive?

A

passive

26
Q

In the descending part of the vasa recta describe what happens to solutes and water

A

solutes move into vasa recta
water moves out of vasa recta

blood osmolarity increases

27
Q

in the ascending limb of the vasa recta describe what happens to solutes and water?

A

solutes move out
water moves into blood

blood osmolarity decreases

28
Q

Describe the osmolarity of the blood as it enters the vasa recta in comparison to plasma? as it exits?

A

iso-osmotic for both

29
Q

When is the collecting duct more permeable to urea?

A

during antidiuresis in the presence of ADH

30
Q

during diuresis describe urea recycling?

A

does NOT occur, most of urea is excreted

Unit 7: Physiology (19 decks)

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