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V - KCU - RN (T2) - OMS1 > Regulation Of Body Fluid Osmolality: Regulation Of Water Balance > Flashcards

Regulation Of Body Fluid Osmolality: Regulation Of Water Balance Flashcards

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1
Q

How does the LoH act as a countercurrent multiplier

A

By producing a hypertonic medulla by pooling NaCl in the interstitium, it favors a movement of water out of the CD under the regulation of ADH

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2
Q

The ThALoH maintains what gradient between the Tf and the interstitium

A

A 200 mOsmol gradient

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3
Q

The fluid leaving the TDLoH is what?

A

Hypertonic

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4
Q

Tubular fluid entering the descending limb from the PCT is what

A

Isotonic (around 300 mOsmol)

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5
Q

Before the vertical osmotic gradient is established, the medullary IF concentration is what

A

300 mOsmol, just like the rest of the body

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6
Q

The ThALoH pumps NaCl into the IF until when? Then what does this gradient cause

A

The IF is 200 mOsm/L more concentrated than the TF in this limb

This gradient causes water to be REBS from the TDLoH since water follows salt.

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7
Q

Passive movement of water from the TDLoH continues until when

A

The osmolarities of the TF and If are equal

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8
Q

What is the osmotic equilibrium of the LoH’s and IF

A

The ThALoH is 200 mOsm/L and the IF and TDLoH are 400 mOsm/L

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9
Q

The IF always achieves equilibrium with what, ensuring a concentration gradient ranging from 300 to 1200 mOsm/L

A

The TDLoH

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10
Q

What is the role of the vasa recta?

A

blood supply to the medulla

Removes the water and solute that is continuously added to the medullary intersitium

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11
Q

What does an increase or decrease in vasa recta BF mean

A

Increase - dissipates the medullary gradient (medullary washout)

Decreased - reduces the ability to concentrate the urine

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12
Q

What parts of the nephron are impermeable to Urea REBS

A

The ThALoH, the DCT, ands the cortical CD

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13
Q

What transporter allows urea to be transported across the apical membrane to be REBS and re enter at the LoH

A

UT - A1

UT - A3

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14
Q

What teo things overall created the IF osmotic gradient?

A

AQP within the TDLoH which allows water to be REBS into the IF

The anatomy of the LoH and CD which allows for progressively increasing osmolality

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15
Q

What are the two neurons that synthesize ADH in the brain

A

The supraoptic and paraventricular nuclei of the hypothalamus

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16
Q

Where is ADH released from

A

The posterior lobe

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17
Q

Generally, what is activated first, ADH or thirst?

A

ADH

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18
Q

What is used to actively transport Na across the basolateral membrane into the IF

A

Na/K Pump

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19
Q

ADH effects what AQP on which cells

A

AQP - 2 on principal cells

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20
Q

What is the role os Aldosterone in the intercalated cells

A

Increasing H secretion by the intercalated cells by stimulating the H/ATPase

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21
Q

What channels does Aldosterone work on

A

ENaC channels (moving Na into the cell from the TF)

22
Q

The CDC are _____ to water at all times

A

Permeable

23
Q

The permeability of the MCD is determined by what

A

ADH/AQP - 2

24
Q

What happens in regards to ADH if you are overhydrated or dehydrated

A

Overhydrated - ADH inhibited

Dehydrated - ADH activated

25
Q

An adequately hydrated person has a plasma osmol of what

A

275 - 295

26
Q

Define Central Diabetes Insipidus

A

An inability to produce or release ADH from the posterior pituitary usually caused by a head injury

DCT can not REBS water so a large volume of dilute urine is created (polyuria) while the plasma becomes increasingly hyperosmotic leading to hypernatremic dehydration

27
Q

Restricting water intake in a patient with central DI can cause what

A

Sever dehydration

28
Q

What is the Tx for Central DI

A

Administration of desmopressin which acts selectively on V2 receptors to increase water permeability in the late DCT and CD

29
Q

Define Nephrogenic DI

A

A failure of the kidneys to respond to ADH

Elevated levels of ADH in the renal tubule, but no more AQP-2 made

This means increased diuresis and dehydration

Adding an antidiuretic like furosemide can greatly compromise the urine concentrating ability

30
Q

Define SIADH

A

Excessive release of ADH and thus excessive water REBS

Causes cells to swell and the body to hold onto electrolyte free water which causes hyponatremic dehydration

31
Q

Dilution of urine is dependent on what

A

The ThALoH to REBS more solutes without water

And the CD to not REBS as much H2O (less ADH)

32
Q

So, what happens in excess water/decreased NaCl intake

A

Increased H20 intake = increased NKCC/decreased ADH & AQP - 2 = increased diuresis = hyposomotic urine and hyperosmotic plasma

33
Q

So, what happens in decreased water intake or excess salt intake

A

Decreased water = increased ADH & AQP-2 = decreased diuresis = hyperosmotic urine/hypoosmotic plasma

34
Q

What is the most abundant electrolyte disturbance in hospitalized patients

A

Hyponatremia

35
Q

What causes hyponatremia

A

Too much ADH caused by pain, nausea, decreased arterial volume, exercise

36
Q

What causes hypernatremia

A

Inadequate free water intake and impaired thirst as well a volume depletion

37
Q

What is considered polyuria and what causes it

A

> 2.5L/day

DB, DI, excess caffeine/alcohol, SSA

38
Q

What is considered oliguria and what causes it

A

300 - 500 ml/day

Dehydration, blood loss, cardiogenic shock,

39
Q

What is considered anuria and what causes it

A

<50ml/day

Kidney failure, obstruction

40
Q

What are the 4 things that can cause polyuria

A
  1. Increased water intake
  2. Increased GFR (hyperthyroidisim/fever/hypermetabolic states)
  3. Increased outputs of solutes (thus more output of water)
  4. Inability of the kidneys to REBS water in the DCT
41
Q

Define water diuresis and hat causes it

A

Increased water excretion without corresponding increase in salt excretion

Primarily caused by increased intake of water/polydipsia, DI

42
Q

What is solute diuresis and what causes it

A

Increased water excretion concurrent with increased salt excretion

Caused by significant increases in salt in TF, aka hyperglycemia, high protein diet

43
Q

A positive water clearance means what

A

Excess water is being excreted by the kidneys

This means decreased ADH/AQP - 2 and increased NKCC2

44
Q

What does a negative water clearance mean

A

Excess solutes are removed from the blood by the kidneys and water is being conserved

This means increased ADH/AQP - 2

45
Q

If urine osmol is greater than plasma osmol, what has happened

A

Free water clearance will be negative, indicating water conservation

46
Q

What occurs in DI

A 
High urinary output 
Low levels of ADH
Hypernatremia 
Dehydrated 
Lose too much fluid 
Excessive thirst
47
Q

What occurs in SIADH

A 
Low urinary output 
High levels of ADH
Hyponatremia 
Overhydrated 
Retain too much fluid 
Excessive thirst
48
Q

What is normal plasma osmol

A

285 - 295

49
Q

Is there too much or too little aldos. In SIADH? Why?

A

Too little

Because SIADH causes the body to create way too much ADH, the body holds onto free water. This increases the ECFV, causing the SNS to not stimulate the RAAS complex and thus not secrete aldos. This diminished aldos secretion causes the body to not absorb NaCl, leading to hyponatremia and concentrated urine.

50
Q

In SIADH, there is increased ECFV. What 4 things does this cause to happen?

A

Reduced plasma osmol
Hyponatremia
Diminished aldos
Elevated GFR

51
Q

What do the principal cells do when acted on my aldos. And what does this mean physiologically

A

REBS NaCl, and secrete K

This means with that with increased aldos, there is hypokalemia

V - KCU - RN (T2) - OMS1 (5 decks)

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