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Renal > Ch. 34 Berne and Levy: Control of Body Fluid Osmolality and Volume > Flashcards

Ch. 34 Berne and Levy: Control of Body Fluid Osmolality and Volume Flashcards

1
Q

What are the 2 physiological regulators of ADH secretion?

A

1) osmolality of body fluids

2) volume and pressure of vascular system (hemodynamic)

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2
Q

During diuresis, ADH activity and production is ______ (low or high)

A

low

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3
Q

True or false: urea plays a major role in effecting ADH secretion

A

FALSE (urea is an ineffective osmole with respect to osmoreceptors)

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4
Q

When plasma osmolality INCREASES, ADH synthesis _________

A

INCREASES (want to save water to bring that plasma osmolality down)

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5
Q

What are the 3 actions of ADH?

A

1) INCREASE water permeability in the collecting duct
2) INCREASE medullary permeability of urea in collecting duct
3) stimulate NaCl reabsorption in the thick ascending limb and collecting duct

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6
Q

How does ADH affect the urea cycle?

A

INCREASES permeability of terminal portion of the inner medullary collecting duct to urea (INCREASES reabsorption of urea to increase osmolality of medulla)

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7
Q

True or False: fluid entering descending limb is isosmotic to plasma?

A

TRUE

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8
Q

Rank sections of the kidney in order of lowest to highest osmolality: outer medulla, inner medulla, cortex

A

cortex < outer medulla < inner medulla

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9
Q

What is known as the diluting segment and why is it called that?

A

the thick ascending limb - allows for active NaCl reabsorption

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10
Q

True or False: fluid leaving thick ascending limb is isosmotic to plasma

A

FALSE; it is hyposmotic

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11
Q

What effect do the distal tubule and collecting duct have on osmolality?

A

DECREASE it (further reabsorb NaCl)

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12
Q

What establishes the hyperosmotic medullary interstitial gradient?

A

counter current multiplier

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13
Q

Describe the steps that compromise the counter current multiplier

A

1) Water permeability of descending limb (passively moves out of tubule increasing osmo of tubular fluid)
2) Salt passively moves out of ascending limb, DT and CD

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14
Q

Where is the site of highest osmolality in tubular fluid

A

bend of loop of Henle

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15
Q

In the presence of ADH, what makes the urine concentrated, NaCl or urea?

A

urea

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16
Q

How is the hyperosmotic gradient maintained during antidiuresis when water is reabsorbed?

A

water is reabsorbed mostly from the cortex > outer medulla > inner medulla

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17
Q

What are the two most abundant species in the medulla?

A

NaCl and urea

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18
Q

Where is the only place along the nephron where urea can enter?

A

Descending limb of loop

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19
Q

Why is urea an ineffective osmole when it comes to driving water reabsorption?

A

inner medullary collecting duct is highly permeable to urea (especially in presence of ADH)

Therefore, urea just equilibrates tubular conc to interstitual conc.

20
Q

Where does active salt pumping occur?

A

TAL, DT, CD

21
Q

What happens to urine flow as vasa recta flow increases?

A

INCREASES

22
Q

Which is greater, vasa recta water or salt?

A

salt

23
Q

What is negative free water clearance?

A

Uosm > Posm (trapped water, think of it as negative (ie very little) water in the urine)

24
Q

What are the 3 main chemical determinants of ECF osmolality?

A

Na, Cl, HCO3

25
Q

What is ECV?

A

effective circulating volume (portion of ECF within vascular system that is effectively perfusing tissues)

26
Q

What happens to ECV as arterial pressure and cardiac output increase?

A

INCREASES

27
Q

How do the low-pressure sensors work to detect effective circulating volume?

A

cardiac stretch receptors on the venous side of circulation detect increased stretching (more volume) and secrete ANP which induces natriuresis

in cardiac atria and pulm vasculature

28
Q

When cardiac stretch receptors are activated, what happens to sympathetic stimulation?

A

DECREASES, ADH decreases, water diuresis

29
Q

Where are the high pressure sensors and how do they affect sympathetics?

A

aortic arch and carotid baroreceptors as well as JGA (detects slow tubular flow and decreases symp stim, increasing Na excretion)

DECREASE sympathetics

30
Q

What are the other two sensors in addition to low and high pressure?

A

hepatic and CNS

31
Q

How does sympathetic stimulation affect Na reabsorption?

A

INCREASES it

32
Q

How does ANP affect GFR?

A

increases it (end goal of decreasing water and salt reabsorption to increase urine volume)

33
Q

What are the three efferent effectors regulating ECV?

A

Two salt retention

1) renal symp nerves
2) renin-angiotensin-aldosterone

one salt excretion
3) ANP

34
Q

What are the 3 factors important in stimulating renin secretion?

A

1) Perfusion pressure (increase perf pres, decrease renin)
2) Symp nerve activity (increase symp, increase renin)
3) Delivery of NaCl to macula densa (increase NaCl delivery, decrease renin?)

35
Q

What is the enzymatic activity of renin?

A

converts angiotensinogen to AT1

36
Q

What converts AT1 to AT2?

A

ACE (angiotensin converting enzyme)

37
Q

What effect does AT2 have on ADH?

A

stimulates its release

38
Q

What effect does AT2 have on aldosterone?

A

INCREASES release from the adrenal cortex

aldosterone then binds to receptors on the DT and CD and signals for production of new Na,K ATPase pumps which increases Na reabsorption and K+ secretion/excretion

39
Q

What stimuli effect the release of ANP?

A

1) INCREASED ECF
2) INCREASED AP (left atrial pressure)
3) INCREASED VP (right atrial pressure)

basically, high pressure or too much volume (think, natriuertic wants to produce urine, wants to do that because there is too much volume)

40
Q

How does ANP secretion effect renin, ADH, Na excretion, symp stim?

A

decreases renin
decreases ADH
increases Na excretion
decreases symps

41
Q

What is euvolemia?

A

Na intake matches excretion

42
Q

Where in the nephron does the 99% reabsorption of Na occur?

A

1) PT: 67%
2) TAL: 25%
3) DT: 4%
4) CD: 3%

43
Q

What are the 3 integrated responses of the nephron to INCREASED ECV?

A

1) increased GFR
2) decreased Na reabsorption in PT
3) decreased Na+ reabsorption in CD

44
Q

Why does an increase in ECV decrease Na reabsorption?

A

because Na in the interstitium pulls water and that continues to increase ECV

45
Q

What are the two most common causes of edema in terms of Starling forces?

A

1) increased hydrostatic pressure

2) decreased oncotic pressure

Renal (6 decks)

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