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Renal Final > Regulation of ECF Volume and NaCl Balance > Flashcards

Regulation of ECF Volume and NaCl Balance Flashcards

1
Q

Primary Cation in Plasma

A

Sodium

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2
Q

Primary Cation in Interstitial Fluid

A

Sodium

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3
Q

What three factors must be balanced in body?

A

Osmolarity
Water
NaCl

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4
Q

What is important in regulating ECF volume long term? what will regulating ECF volume help with?

A
  • maintaining salt balance

Regulating ECF volume will help maintaining blood pressure

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5
Q

What is important in regulating ECF osmolarity long term? what will regulating ECF osmolarity help with?

A
  • maintaining water balance

Regulating ECF volume will prevent swelling or shrinking of cells

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6
Q

Effective Circulating Volume

  • definition
  • is it measurable?
  • proportion of body containing ECV
A

portion of ECF volume that is in arterial system under particular pressure and is effectively perfusing the tissue

  • NOT measurable
  • NOT a distinct body fluid compartment

about 0.7 L of vascular volume forms ECV

ECV is SENSORY

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7
Q

Congestive Heart Failure

- what do patients present physiologically?

A
  • low effective circulating volume due to decreased cardiac output
  • Na and fluid retention-> edema ( venous and capillary hydrostatic pressure increases )
  • Na retention-> increase ECF WITHOUT correcting effective circulating volume
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8
Q

How does body counteract decrease in effective circulating volume/edema? (4)

A

1) Activation of RAAS system
2) stimulation of sympathetic nervous system via barareceptor reflex
3) Increased ADH secretion
4) Increase renal fluid retention via altered Starling’s forces in peritubular capillaries

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9
Q

Osmoreceptors have two functions. What are they?

A

1) To regulate release of ADH

2) To regulate thirst

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10
Q

ADH secretion is controlled by:

A

1) Osmoreceptors
- detect changes in body fluid osmolarity

2) Baroreceptors
- which detect changes in blood volume/ blood pressure

  • osmoreceptor system more sensitive than baroreceptor system
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11
Q

What happens when blood pressure and blood volume are reduced?

A

increase ADH secretion

increased fluid reabsorption by kidneys

help to restore blood pressure and blood volume toward normal

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12
Q

How sensitive is ADH secretion to blood pressure?

What about acute rise in BP?

A

if blood pressure falls by 20%, ADH increases to maintain antidiuresis

small decreases in BP (5-10%) have little effect

Acute rise in BP suppresses ADH secretion

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13
Q

Sensed Volume on osmolality and ADH release

- what happens when there is decreased sensed volume?

A

it “sensitizes” the system

  • smaller changes in osmolality will induce larger amounts of ADH release
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14
Q

Sensed Volume on osmolality and ADH release

- what happens when body senses volume expansion?

A

higher threshold for release of ADH

less vigorous response to progressive hyperosmolarity

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15
Q

Three types of baroreceptors

A

1) Arterial baroreceptors
2) Cardiopulmonary baroreceptors
3) Intrarenal baroreceptors

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16
Q

Arterial baroreceptors

  • location
  • what it deals with (4)
  • function
A

brainstem vasomotor center

  • Total peripheral resistance
  • Cardiac Performance
  • Sympathetic Drive to Kidney
  • Venous compliance
  • Sense pressures in aorta and carotid arteries
  • send afferent information to brainstem vasomotor
    • regulates CV and renal processes via autonomic efferents
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17
Q

Cardiopulmonary baroreceptors

  • locations
  • what it deals with (4)
  • function
  • what is special about it
A

brainstem motor center
Hypothalamus

  • venous compliance
  • sympathetic drive to kidney
  • total peripheral resistance
  • cardiac performance
  • ADH
  • sense pressure in cardiac atria and pulmonary arteries
  • send afferent information in parallel with arterial baroreceptors
  • have more important influence on hypothalamus than arterial baroreceptors ( regulate secretion of ADH)
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18
Q

Intrarenal baroreceptors

- functions

A
  • Renin-angiotensin system

- GFR, salt, and water reabsorption

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19
Q

Regulation of body Na content

  • sensed
  • sensor
  • effector
  • affected
A

ECF volume

  • sensed: effective circulating volume
  • sensor: arterial and cardiac baroreceptors
  • effector: Ang II/aldosteron/ SNS/ ANP
  • affected: Urine Na excretion
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20
Q

Regulation of body fluid content

  • sensed
  • sensor
  • effector
  • affected
A

Plasma osmolality

  • sensed: plasma osmolality
  • sensor: hypothalamic osmoreceptors
  • effector: AVP ( arginine vasopressin)
  • affected: urine osmolality (H2O output) & thirst
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21
Q

How does ADH responds to changes in plasma osmolality ? ( think Na and ECF)

3 steps

A

1) changes in Na intake/output that results in changes in total body Na content can cause change in plasma osmolality
2) body alters water intake and renal water absorption to maintain an isotonic ECF
3) Osmolality is maintained at the expense of ECF volume

22
Q

Effect of decrease in total body Na content

A

eventual ECF contraction

23
Q

Effect of gain in total body Na

A

eventual ECF expansion

24
Q

Homeostasis steps for increase Na in ECF

A

1) stimulate osmoreceptors in hypothalamus
2) secretion of ADH restricts water loss and stimulates thirst
- promote additional water consumption
3) Water shifts ICF-> ECF
- lower ECF Na concentration
4) Na levels in ECF fall (homeostasis)

25
Q

Homeostasis steps for decrease Na in ECF

A

1) inhibit osmoreceptors in hypothalamus
2) decrease secretion of ADH
- suppress thirst
- water loss in kidneys
3) Water loss reduces ECF volume
- concentrates ions
4) Na levels in ECF rise (homeostasis)

26
Q

Vascular Volume Sensors

A
  • detect changes in ECFV
  • signals to kidneys
  • adjustments in NaCl and water excretion
27
Q

If ECFV is expanded what happens?

A

renal NaCl and water excretion are excreted

28
Q

If ECFV is contracted, what happens?

A

renal NaCl and water excretion are reduced

29
Q

Four main effector mechanism for volume sensors

A

1) Renal Sympathetic nerve activity
2) Renin- Angiotensin-aldosterone system
3) Atrial Natriuretic Peptide
4) AVP ( vasopressin)

30
Q

Renal Sympathetic nerve activity

  • function
  • effects
A

reduce NaCl excretion

  • reduce GFR
  • increase renin secretion
  • increase Na reabsorption along nephron
31
Q

Renin- Angiotensin Aldosterone System

  • function
  • effects
A

reduce NaCl excretion

  • increases ang II stimulates Na reabsorption along nephron
  • increase aldosterone stimulate Na reabsorption in distal tubule and collecting duct and to a lesser degree in thick ascending LOH
  • increase angiotensin II stimulates AVP
32
Q

Natriuretic Peptide

  • function
  • effects
A

ANP, BNP, Urodilation

increase NaCl excretion

  • increase GFR
  • decrease renin secretion
  • decrease aldosterone secretion
    (indirect via decrease angiotensin II and direct on adrenal gland)
  • decrease NaCl and water reabsorption by the collecting duct
  • decrease AVP secretion and inhibition and AVP action on distal tubule and collecting duct
33
Q

AVP

  • function
  • effects
A

decrease H2O excretion

-increase H2O reabsorption by distal tubule and collecting duct

34
Q

Mechanisms for secretion of Renin

  • 3 and describe
  • Net Effect
A

1) Perfusion Pressure
- low perfusion in afferent arterioles stimulates renin secretion while high perfusion inhibits renin secretion

2) Sympathetic Nerve Activity
- activation of sympathetic nerve fibers in afferent arterioles increases renin secretion

3) NaCl delivery to macula densa
- when NaCl decreased, renin secretion is stimulated
(Tubuloglomerular Feedback)

  • stimulate release of renin by juxtaglomerular apparatus
    • cleaves angiotensinogen to for angiotensin
35
Q

Renin-Angiotensin- Aldosterone System Steps (6)

A

1) Systemic blood pressure decreases-> decrease in GFR
2) JG cells release renin
3) Renin converts angiotensinogen to angiotensin-1
4) ACE converts angiotensin I to the active angiotensin II
5)
- vasoconstriction of efferent arterioles
- vasoconstriction of systemic blood vessel
- reabsorption of Na and Cl from proximal tubule and H2O follows
- promotes aldosterone release, increasing Na+ H2O reabsorption
6) GFR increases and Systemic blood pressure increases

36
Q

Atrial Natriuretic Peptide

  • where it is produced
  • what does it produce
  • where is it stored
  • function
A
  • Loses Na
  • lowers BP
  • produced in atrial cardiac muscle cells
  • produces natriuresis
  • stored in granules and released when heart muscle cells are mechanically stretched by an expansion of circulating plasma volume when ECF volume
  • responds to increased blood pressure caused by Na+ and H2O retention
  • promote natriuresis and diuresis
  • decrease plasma volume
  • lowers blood pressure
  • inhibit Na reabsorption in distal part of nephron
  • increase Na excretion
  • increase H2O excretion in urine
37
Q

How does Na excretion increase in urine?

-steps

A
  • by inhibiting RAAS

1) ANP inhibit renin secretion by kidneys and act on adrenal cortex to inhibit aldosterone secretion
2) ANP inhibit the secretion of vasopressin

38
Q

Regulation for Salt deficit

A

plasma osmolality low-> water diuresis -> plasma volume and blood pressure decrease -> renin secretion -> increase angiotensin II-> increase aldosterone-> increase Na reabsorption -> salt and water excretion decreases

39
Q

Regulation of Salt Excess

A

plasma osmolality high-> increase ADH and thirst pathway -> plasma volume and blood pressure increase ->atrial pressure increase _> increase ANP-> renin inhbition -> inhibit aldosterone-> decrease Na reabsorption -> salt and water excretion increases

40
Q

Na Excretion with Volume Expansion (5)

- end result

A

1) Decreased activity of renal sympathetic nerve
2) Increased release of ANP and BNP from the heart and urodilation by the kidneys
3) Inhibition of AVP secretion from the posterior pituitary and decreased AVP action on the collecting duct
4) decreased renin secretion and thus decreased production of angiotensin II
5) reduced angiotensin II-> decreased aldosterone secretion and elevated natriuretic peptide levels

  • increase sodium excretion
41
Q

Na Excretion with Volume Contraction (3)

A

1) Increased renal sympathetic nerve
2) Increased secretion of renin which results in elevated angiotensin II levels and thus increased secretion of aldosterone by adrenal cortex
3) Stimulation of AVP secretion by posterior pituitary

42
Q

Hyponatremia

  • values
  • definition
  • clinical presentations
A

Serum sodium < 135 mEq/L
Serum Osmolality <280 mOsm/Kg

  • sodium concentration in plasma is lower than normal
  • body fluid diluted
  • decreased ECF osmolality
  • cell swell

Fluid moves from osmosis from ECF-> ICF

  • edema and hypovolemia
43
Q

ECF volume

  • factors that regulate it
  • effects on arterial blood pressure when not normal
A

Regulated by

  • salt balance maintenance
  • aldosterone

Decrease ECF volume= Decrease arterial blood pressure

increase ICF volume= increase arterial blood pressure

44
Q

ECF osmolarity

  • factors that regulate it
  • effects on cell size when not norma
A

Regulated by

  • H2O balance maintenance
  • Vasopressin

Increase ECF osmolarity (hypertonicity) -> H2O leaves cells -> cells shrink

Decrease ECF osmolarity (hypotonicity) -> H2O enters the cells-> cells swell

45
Q

Water balance

- what maintains it? what does that lead to?

A

ADH maintains water balance

- leads to retention of excess free water

46
Q

Hyponatremia

A

In> Out

47
Q

Hypernatremia

A

Out> In

48
Q

Sodium Balance/ ECV

  • regulated by what?
  • effect when ECV is high? Low?
A

1) Sympathetic Nervous System
2) RAAS
- ECV low= activated
- ECV high = inhibited

49
Q

Increase sodium consumption leads to?

- symptoms

A

ECV expansion

  • weight gain
  • possible hypertension
50
Q

Decrease sodium consumption leads to?

- symptoms

A

ECV contraction

  • weight loss
  • improvement in hypertension

Renal Final (7 decks)

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