Regulation of ECF Volume and NaCl Balance Flashcards

1
Q
  • High ADH can do what to sodium levels?
A

Can cause hyponatremia

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2
Q
  • When ADH is always high, _ is no longer controlled by ADH
  • _ is then controlled by amount of free water you take in
A

Sodium

Sodium

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3
Q

Urine should be _ in hyponatremia

A

diluted

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4
Q
  • How do you distinguish if the kidneys are responding appropriately to hyponatremia?**
A
  • Urine is diluted
    • Kidneys are responding appropriately
    • ADH levels are low (where they should be)
    • Problem is outside of the kidneys
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5
Q
  • Maintaining _ balance is important for long-term regulation of ECF volume
  • Maintaining _ balance is important for regulating ECF osmolarity
A

Salt

Water

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6
Q
  • ECV (Effective Circulating Volume)
A
  • Portion of the ECG volume that is in the arterial system ubder particular pressure and is effectively perfusing the tissues
  • Not a measurable and distinct body fluid compartment
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7
Q

How much of the vascular volume forms the ECV?

A
  • 0.7 L (20% plasma, 5% of ECF, 1.7% TBW, 1% of body weight)
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8
Q
  • How is effective circulative volume changed in a person with congestive heart failure?
  • How is this counteracted
A
  • CHF patients have a low effective circulating volume (d/t decreased cardiac output)
  • 4 Ways this is counteracted
  • 1) Activation of RAAS system
  • 2) Stimulation of sympathtetic nervous system via baroreceptor reflex
  • 3) Increased ADHsecretion
  • 4) Increaed renal fluid retention via altered Starling’s forces in the peritubular capillaries
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9
Q
  • How is ECF volume changed in a person with CHF?
A
  • Increased (Na+ and fluid retention-edema)
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10
Q
  • Where are osmoreceptors located?
  • What do they respond to?
  • How do they respond?

He included this twice, so probably will be on the test

A
  • Supraoptic and paraventricular areas of the hypothalamus
  • Changes in plasma osmolarity
  • Respond in two ways:
    • Regulate ADH release
    • Regulate thirst
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11
Q
  • ADH secretion is controlled by what two receptors?
  • Which is more sensitive?
A
  • Osmoreceptors, barorecceptors
  • Osmoreceptors
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12
Q

Most important non-osmotic stimulus of ADH release

A

Decrease in sensed body volume/Decline in blood pressure (20% or greater)

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13
Q
  • With volume expansion, secretion of ADH is _
  • With volume contraction, secretion of ADH is _
A
  • Decreased
  • Increased
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14
Q
  • _ baroreceptors have an important influence on the hypothalamus and secretion of ADH
  • _ baroreceptors have major role in RAAS pathway
A
  • Cardiopulmonary (in cardiac atria and pulmonary arteries)
  • Intrarenal
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15
Q

Identify the following types of baroreceptors

A
  • Arterial
  • Cardiopulmonary
  • Intrarenal
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16
Q
  • Problems with Na+ balance manifest as altered _
  • What senses this?
  • What is the effector?
  • What is affected a a result?
A
  • ECF volume
  • Arterial and cardiac baroreceptors
  • Angiotensin II, Aldosterone, SNS, ANP
  • Urine Na+ excretion
17
Q
  • Problems with _ balance manifest as altered plasma osmolality, which is reflected in an alteration in plasma _
  • What is sensed?
  • What is the sensor?
  • What is the affector?
  • What is the effect?
A
  • Water, Na+
  • Changes in plasma osmolality
  • Hypothalamic osmoreceptors
  • AVP/ADH
  • Urine osmolality (H20 output) and thirst
18
Q
  • Decrease in total body Na+ content leads to eventual ECF _
  • Increase in total body Na+ content leads to eventual ECF _
A
  • Contraction
  • Expansion
19
Q
  • How do the renal sympathetic nerves act as volume sensors?
  • What actions do they perform?
A
  • Respond to changes in ECFV delivery to kidney
  • In the event of low ECFV:
    • Decrease GFR
    • Increase Renin Secretion
    • Increase Na+ reabsorption along the nephron
20
Q
  • How does the RAAS system respond to changes in ECFV?
A
  • In the event of low NaCl and water delivery to the kidney
  • Increase of angiotensin II to stimulate Na+ reabsorption along neprhon
  • Aldosterone stimulates Na+ reabsorption in the distal tubule and collecting duct (and to a lesser extent in the ascending LOH)
  • Increased angiotensin II stimulates secretion of ADH
  • ADH increases water reabsorption in the collecting duct
21
Q
  • How do naturiretic peptides (ANP, BNP, Urodilatin) respond to changes in ECFV?
A
  • Increased secretion leads to increased NaCl excretion
    • Increase in GFR
  • Decrease in renin secretion
  • Decreased aldosterone secretion (indirect via angiotensin II and direct on adrenal gland)
  • Decrease NaCl and water reabsorption by the collecting duct
  • Decrease ADH secretion
22
Q
  • How does AVP/ADH respond to changes in ECFV?
A
  • Increases H2O reabsorption by the distal tubule and collecting duct
23
Q
  • 3 mechanisms for the regulation of renin release
A
  1. Perfusion pressure
    1. Low perfusion pressure in afferent arterioles stimulates renin secretion
    2. High perfusion pressure in afferent arterioles inhibits renin secretion
  2. Sympathetic nerve activity
    1. Activation of sympathetic nerve fibers in afferent arterioles increases renin secretion
  3. NaCl Delivery to the macula densa (tubuloglomerular feedback)
    1. When NaCl delivery to the macula densa is decreased, renin secretion is stimulated
24
Q
  • Renin is responsible for catalyzing which reaction?
A
  • Conversion of angiotensinogen to angiotensin I
25
Q
  • Where is ANP produced?
  • When is ANP released?
  • What are the effects of ANP?
A
  • Atrial cardiac muscle cells
  • ECF volume is increased and receptors are stretched in muscle cells
  • Directly inhibit Na+ reabsorption in the distal parts of the nephron (increasing Na+ excretion and accompanying osmotic H2O excretion in the urine)
  • Also increases Na+ excretion by inhibiting RAAS
    • Inhibits renin secretion by the kidneys and acts on adrenal cortex to inhibit aldosterone secretion
    • Inhibits secretion and action of vasopressin
26
Q
  • What happens to Na+ with volume expansion?
A
  • Decreased activity of renal sympathetic nerves
  • Increased release of ANP and BNP from the heart and urodilatin from the kidneys
  • Inhibition of ADH/AVP secretion from posterior pituitary and decreased ADH action on the collecting duct
  • Decreased renin secretion and thus decreased production of angiotensin II
  • Decreased aldosterone secretion
  • OVERALL INCREASE IN NA+ AND H2O EXCRETION
27
Q
  • What happens to Na+ with volume contraction?
A
  • Sodium is reabsorbed
  • Increase in sympathetic nerve activity in the kidney
  • Increased secretion of renin, angiotensin and aldosterone
  • Stimulation of ADH secretion by the posterior pituitary
  • NET EFFECT IS LESS Na+ and H2O SECRETION AND MORE REABSORPTION
28
Q
  • Hyponatremia
    • Serum Na+ levels
    • Serum Osmolality
  • What types of fluid shifts will occur
A
  • Serum Na+ < 135 mEq/L and serum osmolarity <280 mOsm/kg
  • Since serum Na+ levels are decreased, more water will shift from the ECF to the ICF and can cause cerebral edema and hypovolemia
29
Q
  • Mechanisms for regulating ECF volume
  • Outcomes if the variable is not normal
A
  • Maintenance of salt balance; accomplished by aldosterone controlled adjustments of Na+ excretion in the urine
  • If salt balance is not properly regulated
  • Decrease in ECF volume leads to a decrease in arterial BP
  • Increase in ECF volume leads to an increased in arterial BP
30
Q
  • What are the mechanisms for regulating ECF osmolarity?
  • What happens if osmolarity is not normal?
A
  • H2O balance; Vasopressin controlled adjustments in the excretion of H2O in the urine
  • If there is an increase in ECF osmolarity, fluid will leave cells and cells will shrink
  • If there is a decrease in ECF osmolarity, fluid will shift into the cells and the cells will swell