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David's- Renal Exam 2 > Regulation of the ECF Volume and NaCl Balance > Flashcards

Regulation of the ECF Volume and NaCl Balance Flashcards

1
Q

What are the primary cations and anions in the ECF?

A

Cations: Na+

Anions: Cl- and HCO3-

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2
Q

ECF volume must be regulated to help us maintain our ________.

Regulating ECF volume in the long-term involves maintaing _________.

A

ECF volume must be regulated to help us maintain our blood pressure.

Regulating ECF volume in the long-term involves maintaing salt (NaCl).

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3
Q

ECF osmolarity must be closely regulated to ________________.

Regulating ECF osmolarity is most importantly done by _________.

A

ECF osmolarity must be closely regulated to prevent swelling or shrinking of cells.

Regulating ECF osmolarity is most importantly done by maintaing water balance.

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4
Q

What is the effective circulatory volume (ECV)?

A

ECV–> the amount of fluid in the arterial system, under enough pressure to perfuse the tissues. However, it cannot be measured directly because it is not its own compartment.

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5
Q

About how much of the vascular volume makes up the ECV?

A

0.7 L.

5% of the ECF or 20% of the plasma.

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6
Q

Becca comes in with CHF.

What can we determine about her ECV?

A

Becca will have low ECV d/t a decreased CO that patients with CHF experience.

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7
Q

Becca has CHF and thus, has a decrease in her effective circulating volume (ECV).

How do we counteract that?

A

[insert pic]

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8
Q

Recall that an increase or decrease of sodium in a compartment typically changes the volume of that compartment, rather than the osmolality.

In CHF, patients continue to retain sodium, which causes what?

A

Increases the extracellular fluid volume WITHOUT correcting the effective circulating volume.

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9
Q

RECAP: How is ADH secreted?

A

Osmoreceptors triggers ADH secretion from the supraoptic and PVN in response to changes in plasma osmolality.

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10
Q

What are the 2 functions of osmoreceptors?

A

1. Release ADH.

2. Regulate thirst.

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11
Q

RECALL: ADH secretion is controlled, primarily by what two mechanisms?

A
  1. Osmoreceptors, which detect changes in plasma osmolarity.*
  2. Baroreceptors, which detect changes in the blood volume.

*=more sensitive.

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12
Q

Decrease in BP and BV–>

A

Increased ADH secretion

–>

Increases fluid reabsorption, to help restore BP and BV to normal.

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13
Q

What is the most important non-osmotic stimulus of ADH release?

A

Decrease BP.

-Small decreases (5%-10%), have little effect. However, if the BP falls by 20%, ADH rises beyond what we need to maintain antidiuresis.

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14
Q

Acute rise in BP (if BP rises quickly enough), what will happen to ADH secretion?

A

It will be supressed.

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15
Q

How do decreases in blood volume (hypovolemia/volume contraction) affect ADH release?

A

Decreases in BV –> sensitize the system so that smaller osmolar changes cause larger amount of ADH release.

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16
Q

How does an increase in BV (hypervolemia/volume expansion) affect ADH release?

A

“desensitizes” the system, requiring larger changes in osmolality to induce the same ADH release.

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17
Q

What are the three types of baroreceptors that affect renal process?

A

1. Arterial baroreceptors

2. Cardiopulmonary baroreceptors

3. Intrarenal baroreceptors

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18
Q

How do arterial baroreceptors affect renal processes?

A

Arterial baroreceptors sense pressures in the [aorta and carotid arteries] –>

send afferent information to the [brain vasomotor center]–>

regulates renal processes via the autonomic efferents (affect TPR, cardiac performance, sympathetic drive to kidney & venous compliance).

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19
Q

How do cardiopulmonary baroreceptors affect renal processes?

A

Cardiopulmonary receptors sense pressure in the atria and pulmonary arteries.

They do the same thing as arterial baroreceptors; with one added thing: They send information to hypothalamus, which affects ADH secretion.

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20
Q

How do intrarenal baroreceptors affect renal processes?

A

Have a role in:

1. RAAS system

2. GFR

3. water reabsorption

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21
Q

Problems with Na+ balance typically affect what ________.

A

ECF volume (determined by amount of Na+)

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22
Q

Problems with water balance typically affect what?

A

Plasma osmolality (body water content), which is reflected by changes in plasma Na+

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23
Q

ECF volume (amount of Na+)

Changes in amount of Na+ is sensed by measuring _______ via ___________.

This causes changes in _________________, which will effect _____________.

A

Changes in amount of Na+ is sensed by measuring Effective circulating volume via arterial and cardiac baroreceptors.

This causes changes in ANG II, aldosterone, SNS and ANP, which will effect amount of Na+ excreted.

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24
Q

Plasma osmolality (body water content)

Changes in amount of body water is sensed by measureing _______ via ___________.

This causes changes in _________________, which will effect _____________.

A

Changes in body water are caused by changes in plasma osmolarity, which is affected by Na+.

It is sensed by osmoreceptors, which causes changes in ADH and affects our urine osmolality and thirst.

25
Q

If we eat something really salty (with a high Na+), can it change plasma osmolality?

A

YES.

26
Q

What is the process that occurs when we eat something salty?

A

[pic]

27
Q

When we eat too many chips (increase Na+)

our body alters water intake and water reabsorption in the kindey to do what?

A

maintain a isotonic ECF.

28
Q

When we eat too many chips,

osmolality is maintained at the expense of _______

A

ECF volume.

29
Q

Thus, a gain in total body Na+ causes what?

A

Eventual ECF expansion, as water leaves the ICF–> ECF.

30
Q

Thus, a decrease in total body Na+–>

A

eventual ECF contraction

31
Q

What happens when we have a decrease in Na+ concentration in the ECF?

A

[pic]

32
Q

What happens when the ECFV increases (expanded)?

A

Kidneys try to excrete NaCl- and water .

33
Q

What happens when the ECFV is contracted?

A

NaCl and water excretion are reduced.

34
Q

When the ECF volume increases, they kidneys excrete Na+ and H20.

What 4 mechanisms does this occur by?

A
  1. RAAS system
  2. Renal sympathetic nerve activity
  3. Natriuretic peptides (ANP, DNP, urodilatin)
  4. ADH
35
Q

Renal sympathetic nerves

Increase in activity –>

A

Decrease in NaCl excretion by:

  1. Decreasing GFR–>
  2. Increases renin secretion–>
  3. increases Na+ reabsorption along the nephron
36
Q

RAAS

Increase in secretion–>

A

Decrease in NaCl excretion by:

  1. Angiotensin II –> + Na+ reabsorption along the nephron
  2. Angiotensin II–> + ADH release
  3. Aldosterone –> + Na+ reabsorption in the DT and CD (and to some degree the thick ascending loop of Henle)
37
Q

Naturetic peptides

Increase in secretion –>

A

Increase NaCl excretion by:

  1. Increase GFR
  2. Decrease renin secretion
  3. Decrease aldosterone secretion indirectly (because of decreased renin secretion decreasing angiotensin II)
  4. Decrease aldosterone secretion directly (by acting on the adrenal gland)
  5. Decrease NaCl and water reabsorption by the collecting duct
  6. Decrease ADH secretion, and inhibit ADH action on the distal tubule/collecting duct
38
Q

ADH

Increase in ADH secretion–>

A

Decrease H20 excretion by–>

  1. Increasing H2O reabsorption by the distal tubule and collecting ducts
39
Q

What are the 3 major mechanisms for regulating renin?

A
  • Perfusion pressure
    • Low perfusion in the afferent arterioles (as an low blood pressure) –> + renin secretion.
    • High perfusion–> - renin secretion.
  • Sympathetic nerve activity
    • Activation of the sympathetic nerve fibers in the afferent arterioles –> + renin secretion
  • NaCl delivery to the macula densa
    • When NaCl is decreased–> + renin secretion
40
Q

Recall that NaCl delivery when BP/BV ________.

A

increases

41
Q

General function of ANP

A

[pic]

42
Q

How does ANP affect natriuresis and diuresis?

A

+ natriuresis and diruresis–> decreasing plasma volume

and directly influences CV system to lower BP.

43
Q

Main action of ANP?

A

DIRECTLY inhibit Na+ reabsorption in the distal parts of the nephon–> increasing Na+ excretion and H2O excretion.

44
Q

What happens when we have a salt deficit?

Osmolality decreases–>

A
  • Renal sympathetic nervous system activity increases.
  • ADH decreases to compensate.
  • This results in the ejection of water through the urine (water diuresis).
  • This water diuresis decreases blood volume, and therefore blood pressure.
  • This decrease in blood pressure + the nucleus tractus solitarius and, coupled with the increase in renal SNS activity, the production of renin from the kidneys.
    • The nucleus tractus solitarius creates more central angiotensin II. How?
    • The nucleus tractus solitarius also increases sympathetic activity to the kidney, which increases renin production as well.
    • Renin increases angiotensin II, and therefore aldosterone, which increases sodium reabsorption.
45
Q

What happens when we have a salt excess?

Osmolality increases–>

A

Thirst increases as a direct response to the change in osmolality.

ADH also increases to compensate.

Renal sympathetic nervous system activity decreases.

Increased ADH results in increased water retention, just as increased water intake (due to thirst) increases available water.

Both functions increase plasma volume and blood pressure.

The increase in blood pressure and plasma volume, as well as a decrease in renal sympathetic nervous system activity inhibits renin, and activates atrial natriuretic peptide.

Atrial natriuretic peptide directly decreases the amount of sodium reabsorbed by the kidney, as well as inhibiting the sodium reabsorption pathways RAAS and ADH.

It appears that ADH blocks aldosterone specifically (which makes sense, as the “salt retaining hormone”), as well as blocking ADH production and activity in the nephron.

Also, because the high blood volume / blood pressure blocks renin, it also blocks the downstream effects of renin – which is increased angiotensin II and increased aldosterone production.

This functionally inhibits sodium chloride reabsorption.

46
Q

[look at putting the picture together slide]

A
47
Q

What occurs during volume expansion?

A

Volume expansion

  1. Decreased sympathetic activity
  2. Decrease renin release
    1. Decreased production of angiotensin II
    2. Decreased production of angiotensin II
    3. Decreased release of aldosterone from the adrenal CTX.
  3. Increase ANP and BNP release from the heart and urodilatin by the kidneys
    1. Goes to the brain
    2. Decrease release of ADH from the posterior pituitary
    3. Decrease ADH action on the CD
48
Q

What occurs during volume contraction?

A
  1. Increased renal sympathetic nerve activity
  2. Increased secretion of renin
    1. –> increased release of angiotensin I
    2. –> increase release of angiotensin II
    3. –> increase release of aldosterone from the adrenal CTX
  3. Decrease ANP and BNP
  4. Increased ADH secretion from brain
49
Q

Hyponatremia is when Na+ concentration in the plasma (outside of the cell) is lower than normal.

It is defined as having:

A
  • BOTH
  • Serum Na+ <135 mEq/L
  • Serum osmolality <280 mOsm/kg
50
Q

What occurs during hyponatremia?

A
  • During hyponatremia, we have a decrease of Na+ in the ECF, compared to water.
  • Water will move from the ECF–> ICF–> causing the cells to swell.
  • Due to the loss of volume in the ECF, we will develop hypovolemia (volume contraction) and edema.
51
Q

DESCRIBE EVERYTHING THAT HAPPENS WITH HYPONATREMIA

A

BLUE CHART IN BLOOD.

52
Q

Regulating the ECF volume is important. WHy?

A

Long term control of BP.

53
Q

Decrease in ECF volume –> ____ BP

A

Decrease

54
Q

How do we regulate ECFV?

A

Maintain Na+; primarly by aldosterone controlled adjustments in urinary Na+ excretion

55
Q

Why is regulating ECF osmolarity important?

A

Prevent detrimental osmotic movement of H2O between ECF and ICF

56
Q

Increase in ECF osmolarity (hypertonicity)–>

A

H20 leaves the cells

–> cell shrink

57
Q

Decrease in ECF osmolarity (hypotonicity)–>

A

–> H20 enters the cells–>

cells swell

58
Q

What is the mechanism for regulating ECF osmolarity?

A

Maintaing H20 is complishedb maintly by ADH.

59
Q
A

David's- Renal Exam 2 (12 decks)

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