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Urinary > Session 4- Volume control > Flashcards

Session 4- Volume control Flashcards

1
Q

What does water in ECF most depend on

A

Na+

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2
Q

When we say Na reabsorption, what do we infer goes with it?

A

Cl-

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3
Q

Why can’t we just move water?

A

That would change osmolarity and we want to keep ECF isosmotic

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4
Q

If dehydrated how much water can be absorbed in CD?

A

25%

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5
Q

What is the target of aldosterone?

A

Acts in late DCT and CD principle cells

Specifically on ENaC and ROMK (increase Na in and increase K out)

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6
Q

If renal artery BP increases, how does that affect Na and H20?

A

PCT reabsorption goes down because NHE and NaKATPase function reduces. Plus its going faster through tubule so harder for things to move in.
Pressure natriuresis and pressure diuresis occur (more sodium and more water excreted)

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7
Q

Aquaporin location and type

A

AQP1 in PCT & DL
AQP7 in lower PCT
AQP 2,3,4 in CD

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8
Q

Three different segments of PCT and differences?

A

S1, S2, S3
S1 has SGLT2 (90% of glucose absorbed here)
S3 has SGLT1

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9
Q

What is bulk transport?

A

Reabsorption is isosmotic with plasma, water moves with solute

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10
Q

Water is only reabsorbed in which direction of tubule…

A

Descending

Like rain!!

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11
Q

What happens in LoH? Relate to structure

A

Descending is all permeable to water and impermeable to ions. passive water secretion, thin walls

Ascending is impermeable to water and permeable to solute. Lots of mitochondria and active transport

  1. So first descending lets water out (=its reabsorbed), then the filtrate arriving at ascending is more concentrated.
  2. So thin ascending lets ions leave into medulla (are reabsorbed) passively paracellulary
  3. Thick ascending NKCC so Na and K and Cl actively reabsorbed, ROMK puts K ions bacl
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12
Q

Which part of the nephron uses the most energy and is the most sensitive to hypoxia

A

Thick ascending limb of LoH

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13
Q

What is tubular fluid leaving nephron compared to plasma?

A

Hypo-osmotic

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14
Q

Water permeability of DCT is….

A

Fairly low

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15
Q

How is water permeability of late DCT and CD increased?

A

With ADH

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16
Q

Name transporters in early and late DCT

A

Early DCT: NCCT, ENaC

Late DCT: ENac

17
Q

Describe omsolarity of tubular fluid before and after the DCT

A

As it arrives it is hypo-osmotic, leaves more hypo-osmotic (i.e. is more dilute)

18
Q

DCT is a major site for ______ reabsorption

A

Calcium

19
Q

Movement of Na through ENaC drives paracellular absorption of…

A

Cl-

20
Q

Describe calcium reabsorption (and what it’s tightly regulated by)

A

Enters via TRPV5, shuttled to basolateral side by calbindin, transported out by NCX
Regulated by PTH

21
Q

What are the two main cell types of the CD and what is their division of labour

A

Principle cells which reasborb Na via ENaC

Intercalated cells which reabsorb Cl-

22
Q

Two types of IC cells?

A

Type A secretes H+, type B secretes HCO3

23
Q

How is ADH controlled

A

Osmoreceptors in the OVLT of hypothalamus (also linked with nearby baroreceptors) detect low water. Signal to post pit to release ADH. Also signal to brain for thirst behaviour

24
Q

What’s the only real way to control osmolality

A

Change water intake

25
Q

By what % has osmolarity already changed if you’re thirsty

A

10%

26
Q

Where does ADH act?

A

late DCT and CD on AQP2 in apical membrane

27
Q

Causes of diabetes insipidus?

A

Central- doesn’t make enough ADH e.g. basilar skull fracture, meningitis, encephalitis, tumour, hypo/pit damage
Nephrogenic- kidney doesn’t respond to ADH

28
Q

What is SIADH

A

Syndrome of Inappropriate ADH secretion, make too much

29
Q

Sign of SIADH

A

Dilutional hyponatremia, oedema

30
Q

Describe the cellular structure of the PCT

A

Brush border, lots of mitochondria, star shaped lumen

31
Q

Compare and contrast SIADH and diabetes insipidus

A

Insipidus- not making ADH. All water not reabsorbed so polydipsia and hypovolemic and thirsty

SIADH- excessive ADH. Too much water reabsorbed so concentrated ursine but euvolemic because ANP causes natriuresis. Hyponatremic

Both can be caused by Head injury

32
Q

Define hyponatremia

A

Less than 135mmol/L

33
Q

Causes of hyponatremia

A

By far most common is too much water

True Na loss from d and v, renal failure, burns

Urinary (11 decks)

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