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Renal Test 2 > Regulation of ECF Volume & Na/Water Balance > Flashcards

Regulation of ECF Volume & Na/Water Balance Flashcards

1
Q

what part of Total Body Water (TBW) actually contributes to the effective circulating volume (ECV)

A

ECF

Specifically:
ECF–>Plasma–>arterial plasma (not the venous)

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2
Q

what are the 4 ways to counteract a decreased ECV

A
  1. activate RAAS
  2. increase ADH secretion
  3. stimulate SNS via baroreceptors
  4. increase renal fluid via peritubular capillary forces
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3
Q

why do CHF (congestive heart failure) patients have problems with ECV

A 
a low ECV means the following:
low CO
low venous return
increase Na retention --> leads to Edema
increased capillary hydrostatic pressure
*ECV is uncoupled from the ECFV
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4
Q

how do you regulate ECF volume

A

through salt balance

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5
Q

how do you regulate ECF osmolarity

A

water balance

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6
Q

what receptors sense salt balance

A

baroreceptors

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7
Q

what effectors are triggered as a result of baroreceptor sensing

A

angiotensin II –> and therefore aldosterone
ANP
SNS

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8
Q

what do the effectors of baroreceptor sensing affect

A

urine sodium excretion is affected which alters the ECF volume

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9
Q

how do you regulate ECF (plasma) osmolality

A

through water balance

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10
Q

what receptors sense water balance

A

osmoreceptors

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11
Q

what effectors are triggered as a result of osmoreceptors sensing

A

ADH/AVP

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12
Q

what do the effectors of osmoreceptors sensing affect

A

urine osmolality (water output) AND thirst

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13
Q

what receptor senses changes in body fluid osmolality

A

osmoreceptors

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14
Q

4 characteristics of osmoreceptors that make them effective

A
  1. high sensitivity
  2. low threshold
  3. increase ADH secretion
  4. RAPID change
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15
Q

where do osmoreceptors send signals to

A

hypothalamus which triggers the supraoptic and paraventricular nerves to make ADH/AVP

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16
Q

where is ADH/AVP released from

A

posterior pituitary (neurohypophysis)

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17
Q

what receptor senses changes in blood volume

A

baroreceptors

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18
Q

what are the 3 types of baroreceptors and where in the body are they located

A
  1. arterial (sense changes in the aorta & carotids)
  2. cardiopulmonary (sense changes in the atria & pulmonary arteries)
  3. Intrarenal (sense changes in the kidney)
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19
Q

where do arterial baroreceptors exert their effects

A

afferents –>brainstem vasomotor center

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20
Q

what are functions do arterial baroreceptors affect

A
  1. TPR
  2. venous compliance
  3. SNS actions
  4. cardiac actions
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21
Q

where do cardiopulmonary baroreceptors exert their efffects

A

afferents –> brainstem vasomotor center
AND
hypothalamus

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22
Q

when cardiopulmonary baroreceptors exert their forces on the afferents, what functions are affected

A
  1. TPR
  2. venous compliance
  3. SNS actions
  4. cardiac actions
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23
Q

when cardiopulmonary baroreceptors exert their forces on the hypothalamus, what functions are affected

A

ADH secretion

24
Q

what functions to intrarenal baroreceptors affect

A
  1. RAAS
  2. GFR
  3. salt and water reabsorption
25
Q

when renal sympathetic activity is increased, what is the result

A

decreased salt secretion & excretion

salt retention

26
Q

How do renal sympathetic nerves cause salt excretion

A

a decreased GFR (and low salt sensing by the macula densa) will trigger JG cell to increase renin secretion

this increases Na reabsorption

27
Q

when RAAS activity is increased, what is the result

A

decreased salt excretion

28
Q

what volume sensor activity decreases salt excretion

A

increased activity of the renal sympathetic nerves and RAAS

29
Q

action(s) of angiotensin II

A

Na+ reabsorption in to the blood

triggers adrenal cortex to release aldosterone

30
Q

action of aldosterone

A

Na+ reabsortption

31
Q

when AVP/ADH activity is increased, what is the result

A

decreased water excretion (water retention)

32
Q

action(s) of AVP/ADH

A

insert aquaporins in DT/CD to increase water permeability and move more water into the blood

33
Q

name the 3 natriuretic peptides

A

ANP
BNP
urodilatin

34
Q

when natriuretic peptide activity is increased, what is the result

A

increased salt excretion

  • decrease GFR
  • decrease renin
  • decrease aldosterone
  • decrease Na+ reabsorption
  • decrease ADH (no aquaporins) so DT/CD impermeable to water
35
Q

which 3 mechanisms influence renin release

A
  1. perfusion pressure in afferent arterioles
    low perfusion pressure + renin
    high perfusion pressure – renin
  2. sympathetic nerve activity
    SNS activation of afferents + renin
  3. NaCl deliver to macula densa
    low salt sensed by macula densa + renin secretion
    high salt sensed by macula densa - renin secretion
36
Q

renin regulation by the macula densa is referred to as…

A

tubuloglomerular feedback

37
Q

when RAAS triggers Na+ reabsorption, what are the ultimate outcomes?

A

increased GFR

increased RBF

increased BP

38
Q

where is ANP synthesized

A

atrial cardiac muscle cells

39
Q

what stimulates ANP to be released

A

cardiac muscle stretch
increased ECF volume
increased BP
volume expansion (due to water and Na+ retention)

40
Q

natriuresis

A

excrete Na+ in the urine

41
Q

how does natriuresis work

A

**Inhibits Na+ reabsorption in distal tubule

result:
increase Na+ excretion
increase water excretion
Inhibit RAAS
Inhibit renin secretion
Inhibit aldosterone secretion
Inhibit ADH (no aquaporins inserted to CD)
42
Q

ultimate outcomes of ANP release

A

decreased BP
decreased blood volume (ECF volume)
decreased plasma Na+

43
Q

where is renin released from

A

juxtaglomerular (JG) cells in the kidney

44
Q

what causes volume expansion

A

high blood volume due to Na+ and water retention

45
Q

what does volume expansion lead to

A

Na+ excretion

Inhibition of sympathetics

46
Q

what is inhibited/secreted to resolve volume expansion

A

increase ANP, BNP, urodilatin

inhibit AVP/ADH and aquaporin insertion

decrease renin (angiotensin II) and aldosterone

47
Q

when volume expansion is corrected, what is the outcome

A

decreased ECF volume
decreased BP
decreased blood volume

48
Q

what causes volume contraction

A

too little blood volume due to increased Na+ and water excretion

49
Q

what does volume contraction lead to

A

Na+ retention

Activate sympathetics

50
Q

what is inhibited/secreted to resolve volume contraction

A 
increase the following:
renin
angiotensin II
aldosterone
AVD/ADH
51
Q

where is urodilatin released from

A

kidneys

52
Q

when volume contraction is corrected, what is the outcome

A

increased ECF volume
increased BP
increased blood volume

53
Q

serum values for hyponatremia

A

<135 mEq/L

54
Q

serum osmolality for hyponatremia

A

<285 mOsm/kg

55
Q

what are the physiological consequences of hyponatremia

A

since the blood vessels have more water than sodium, the ECF/plasma is hypotonic in relation to the ICV/cells

cells circulating in a hypotonic environment

fluid will move from the hypotonic ECF into the more concentrated ICF/cells causing the cells to SWELL

RESULT: EDV has less and less fluid

56
Q

hypovolemia

A

decreased volume of circulating blood in the body

**liquid portion of the blood is too low

*caused by hyponatremia

Renal Test 2 (9 decks)

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