Regulation Of Body Fluid Osmolality: Regulation Of Water Balance

Question 1

How does the LoH act as a countercurrent multiplier

Answer 1

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

Question 2

The ThALoH maintains what gradient between the Tf and the interstitium

Answer 2

A 200 mOsmol gradient

Question 3

The fluid leaving the TDLoH is what?

Answer 3

Hypertonic

Question 4

Tubular fluid entering the descending limb from the PCT is what

Answer 4

Isotonic (around 300 mOsmol)

Question 5

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

Answer 5

300 mOsmol, just like the rest of the body

Question 6

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

Answer 6

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.

Question 7

Passive movement of water from the TDLoH continues until when

Answer 7

The osmolarities of the TF and If are equal

Question 8

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

Answer 8

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

Question 9

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

Answer 9

The TDLoH

Question 10

What is the role of the vasa recta?

Answer 10

blood supply to the medulla

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

Question 11

What does an increase or decrease in vasa recta BF mean

Answer 11

Increase - dissipates the medullary gradient (medullary washout)

Decreased - reduces the ability to concentrate the urine

Question 12

What parts of the nephron are impermeable to Urea REBS

Answer 12

The ThALoH, the DCT, ands the cortical CD

Question 13

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

Answer 13

UT - A1

UT - A3

Question 14

What teo things overall created the IF osmotic gradient?

Answer 14

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

Question 15

What are the two neurons that synthesize ADH in the brain

Answer 15

The supraoptic and paraventricular nuclei of the hypothalamus

Question 16

Where is ADH released from

Answer 16

The posterior lobe

Question 17

Generally, what is activated first, ADH or thirst?

Answer 17

ADH

Question 18

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

Answer 18

Na/K Pump

Question 19

ADH effects what AQP on which cells

Answer 19

AQP - 2 on principal cells

Question 20

What is the role os Aldosterone in the intercalated cells

Answer 20

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

Question 21

What channels does Aldosterone work on

Answer 21

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

Question 22

The CDC are _____ to water at all times

Answer 22

Permeable

Question 23

The permeability of the MCD is determined by what

Answer 23

ADH/AQP - 2

Question 24

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

Answer 24

Overhydrated - ADH inhibited

Dehydrated - ADH activated

Question 25

An adequately hydrated person has a plasma osmol of what

Answer 25

275 - 295

Question 26

Define Central Diabetes Insipidus

Answer 26

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

Question 27

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

Answer 27

Sever dehydration

Question 28

What is the Tx for Central DI

Answer 28

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

Question 29

Define Nephrogenic DI

Answer 29

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

Question 30

Define SIADH

Answer 30

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

Question 31

Dilution of urine is dependent on what

Answer 31

The ThALoH to REBS more solutes without water And the CD to not REBS as much H2O (less ADH)

Question 32

So, what happens in excess water/decreased NaCl intake

Answer 32

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

Question 33

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

Answer 33

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

Question 34

What is the most abundant electrolyte disturbance in hospitalized patients

Answer 34

Hyponatremia

Question 35

What causes hyponatremia

Answer 35

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

Question 36

What causes hypernatremia

Answer 36

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

Question 37

What is considered polyuria and what causes it

Answer 37

>2.5L/day DB, DI, excess caffeine/alcohol, SSA

Question 38

What is considered oliguria and what causes it

Answer 38

300 - 500 ml/day Dehydration, blood loss, cardiogenic shock,

Question 39

What is considered anuria and what causes it

Answer 39

<50ml/day Kidney failure, obstruction

Question 40

What are the 4 things that can cause polyuria

Answer 40

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

Question 41

Define water diuresis and hat causes it

Answer 41

Increased water excretion without corresponding increase in salt excretion Primarily caused by increased intake of water/polydipsia, DI

Question 42

What is solute diuresis and what causes it

Answer 42

Increased water excretion concurrent with increased salt excretion Caused by significant increases in salt in TF, aka hyperglycemia, high protein diet

Question 43

A positive water clearance means what

Answer 43

Excess water is being excreted by the kidneys This means decreased ADH/AQP - 2 and increased NKCC2

Question 44

What does a negative water clearance mean

Answer 44

Excess solutes are removed from the blood by the kidneys and water is being conserved This means increased ADH/AQP - 2

Question 45

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

Answer 45

Free water clearance will be negative, indicating water conservation

Question 46

What occurs in DI

Answer 46

``` High urinary output Low levels of ADH Hypernatremia Dehydrated Lose too much fluid Excessive thirst ```

Question 47

What occurs in SIADH

Answer 47

``` Low urinary output High levels of ADH Hyponatremia Overhydrated Retain too much fluid Excessive thirst ```

Question 48

What is normal plasma osmol

Answer 48

285 - 295

Question 49

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

Answer 49

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.

Question 50

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

Answer 50

Reduced plasma osmol Hyponatremia Diminished aldos Elevated GFR

Question 51

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

Answer 51

REBS NaCl, and secrete K This means with that with increased aldos, there is hypokalemia