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Systems Phys 2022 > Renal IIIa > Flashcards

Renal IIIa Flashcards

1
Q

Maintenance of body fluid is tied to….

A

regulation of body sodium content

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2
Q

What effect does plasma membrane Na-K ATPase pump on Na and K?

A

most body Na is retained within ECF

most body K+ is intracellular

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3
Q

Any net increase in total body fluid….

A

is retained in the ECF and body fluid volume increases

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4
Q

Any net loss of total body Na results in…

A

decrease in ECF volume

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5
Q

___ is critical in the maintenance of body fluid volume

A

Regulation of body Na

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6
Q

Increase Na → __ osmolarity → __ H2O

A

Increase Na → increases osmolarity → increases H2O

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7
Q

Increase Total - Body Sodium → __ EC Volume (Plasma Volume/Interstitial Volume) → __blood volume → __ venous pressure → __ atrial pressure → __ ventricular pressure → __ stroke volume → __ cardiac output → __ arterial blood pressure → effects __ and directly effects __

A

Increase Total - Body Sodium → ⇡ EC Volume (Plasma Volume/Interstitial Volume) → ⇡ blood volume → ⇡ venous pressure (MV) → ⇡ atrial pressure (MV) → ⇡ ventricular pressure (MV) → ⇡ stroke volume → ⇡ cardiac output → ⇡ arterial blood pressure → effects monitored variables (MV) and directly effects kidneys

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8
Q

Sodium Excretion Equation

A

Sodium Excretion = Sodium Filtered - Sodium Reabsorbed

= (GFR X PNa) - Sodium reabsorbed

PNa = plasma concentration of Na

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9
Q

It is possible to adjust sodium excretion by…

A

controlling plasma sodium, GFR, and sodium reabsorption

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10
Q

What regulates GFR and sodium reabsorption?

A

the kidneys

monitored by alterations in ECF where effectors that regulate ECF simultaneously regulate sodium reabsorption and excretion

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11
Q

Changes in Plasma Sodium

A

Plasma sodium changes little except to change transiently after ingestion of sodium rich or sodium-free meal/drink

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12
Q

A person is considered in positive Na balance if…

A

excretion is less than Na ingested

retaining water

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13
Q

A person is in negative Na balance when…

A

Na excretion is more than Na ingested

net excreting fluid

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14
Q

Factors that control GFR and Sodium reabsorption in response to altered bodily sodium balance are initiated by….

A
  • Extrarenal baroreceptors
    • carotid sinuses, in arteries, cardiac chambers, great veins
  • Renal Juxtaglomerular (JG) apparatus
    • specifically intrarenal baroreceptors and macula densa which control secretion of renin
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15
Q

Extrinsic control of GFR:

A
  • Renal sympathetic nerves
  • Renin-angiotensin system
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16
Q

Extrinsic control of GFR: Renal Sympathetic nerves

A
  • increased renal sympathetic nerve activation → increased renal arteriolar constriction → decreased PGC → decreased GFR
  • Increases renal sympathetic nerve activation → increased renal arteriolar constriction → decreased renal blood flow → increased average πGC → decreased GFR
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17
Q

Extrinsic control of GFR: Renin-Angiotensin System

A

increased renin release → increased plasma Ang II → decreased GFR and RBF

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18
Q

Local and Direct regulation of GFR:

A
  • Autoregulation
  • Prostaglandins
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19
Q

Local and Direct regulation of GFR: Autoregulation

A

allows maintenance of a relatively constant GFR over a wide range of perfusion pressures

fine tuning

minute to minute regulation of RBF and GFR in the face of changes in BP

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20
Q

Local and Direct regulation of GFR: Prostaglandins

A

PGE2 and PGI2

vasodilators

help make sure too much constriction doesn’t occur

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21
Q

Tubular Sodium Reabsorption is mediated by…

A
  • aldosterone
  • renal sympathetic nerves
  • angiotensin II
  • pressure natriuresis
  • ANP
  • ADH (minor effect)
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22
Q

Where is aldosterone produced?

A

the adrenal cortex

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23
Q

How does aldosterone work?

A

Aldosterone exerts its effect by combining with intracellular receptors and stimulating synthesis of mRNA which mediates translation of specific proteins

The proteins increase the number of luminal-membrane sodium channels and basolateral Na-K-ATPase pumps in the cortical collecting duct (principal cells)

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24
Q

3 Major Inputs to the adrenal gland stimulating aldosterone secretion…

A
  1. Adrenocorticotropic hormone (ACTH)
  2. Increased plasma potassium
  3. Angiotensin II

increase any of these → increase aldosterone secretion

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25
Q

Anything that increases Ang II, ___ aldosterone

A

increases

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26
Q

Aldosterone acts in the ___ and ___ Na reabsorption

A

collecting duct; increases

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27
Q

Control of aldosterone secretion

A

Aldosterone attaches to aldosterone receptor → increases number of sodium channels → increases sodium reabsorption

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28
Q

Tubular effects of renal sympathetic nerves

A
  • stimulates renin secretion via direction action on β1-receptors of granular cells
  • directly stimulates sodium reabsorption in proximal tubule cells
  • affect peritubular capillary Starling Forces and FF → constriction of arterioles will decrease RBF more than GFR
    • results in decreased peritubular capillary hydrostatic pressure and increased peritubular capillary oncotic pressure → increases sodium reabsorption
  • decreased GFR and increased Na reabsorption in proximal tubule → decreases sodium delivery to macula dense which in turn increases renin secretion
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29
Q

Increased constriction, ___ Filtration Fraction (FF)

A

increases

FF increases with sympathetic nervous activity that increases capillary oncotic pressure (driving force of Na reabsorption)

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30
Q

Tubular effects of Ang II: Direct effects

A

Angiotensin II acts directly on proximal tubule cells to stimulate sodium reabsorption → this is done by stimulating the Na-H+ exchanger in the proximal tubule

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31
Q

Tubular effects of Ang II: Effects on FF and Peritubular Capillary Starling Forces

A

Increases FF and thus increases Na and water reabsorption in proximal tubule

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32
Q

Tubular effects of Ang II: Aldosterone

A

increase aldosterone secretion

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33
Q

Tubular effects of Ang II: Ang II

A

Ang II has a profound effect on Na reabsorption by itself

34
Q

What secretes Atrial Natriuretic Peptide (ANP)?

A

Cardiac Atrial Cells

35
Q

How is ANP released?

A

Distention of the atria occurs during plasma volume expansion and ANP is released which acts directly on the inner medullary collecting ducts to inhibit sodium reabsorption

36
Q

Atrial Natriuretic Peptide (ANP)

A

inhibits sodium reabsorption

increases Na excretion

37
Q

ADH (vasopressin)

A

Increases reabsorption of Na from the thick ascending limb, distal tubule and collecting duct

38
Q

Water Excretion

A

Water excretion = volume filtered (GFR) - volume reabsorbed

39
Q

What is the main determinant of water excretion?

A

the rate of water reabsorption → this is mainly determined by ADH levels

40
Q

Control of ADH secretion

A

baroreceptors and/or osmoreceptors

41
Q

What is the major function of ADH?

A

major function of ADH is to increase the permeability of the cortical and medullary collecting ducts to water, thereby decreasing excretion of water

increases Na reabsorption by the cortical collecting duct → effect on total sodium reabsorption is very small

42
Q

Baroreceptor Control of ADH Secretion

A

⇣ plasma volume → ⇣ venous, atrial, and arterial pressures → ⇡ activation of reflexes mediated by cardiovascular baroreceptors → ⇡ ADH secretion → ⇡ Plasma ADH → ⇡ collecting duct permeability to H2O → ⇡ H2O reabsorption → ⇣ H2O excretion

43
Q

Osmoreceptor Control of ADH Secretion

A

Excess H2O ingested → ⇣ extracellular-fluid osmolarity (⇡ H2O concentration) → reflex mediated by osmoreceptors → ⇣ ADH secretion → ⇣ Plasma ADH → ⇣ collecting duct permeability to H2O → ⇣ H2O reabsorbed → ⇡ H2O excreted

44
Q

⇡ Osmolarity (lose water) → __ ADH secretion → __ water reabsorption

A

⇡ Osmolarity (lose water) → ⇡ ADH secretion → ⇡ water reabsorption

45
Q

Thirst response

A

centers that mediate thirst are located in the hypothalamus

thirst is stimulated by reduced plasma volume and increased body-fluid osmolarity

46
Q

⇣ plasma volume → ___ Ang II → stimulates ____ in the kidneys

A

⇣ plasma volume → ⇡ Ang II → stimulates Na reabsorption in the kidneys

47
Q

Effect of Ang II on thirst

A

Ang II stimulates thirst by a direct effect on the brain

Ang II stimulates ADH release from the posterior pituitary which increases water reabsorption

48
Q

Define: Euvolemia

A

normal ECF volume

49
Q

Control of Renal NaCl excretion during Euvolemia

A
  • Na reabsorption by proximal tubule and Loop of Henle is regulated so that a relatively constant portion of filtered Na is delivered to distal tubule.
    • These two segments reabsorb approximately 90% of sodium and ensure that approximately 10% gets delivered to distal tubule
  • Reabsorption of remaining filtered sodium by distal tubule and collecting duct is regulated so that amount of Na in the urine closely matches the amount ingested in diet at steady state
50
Q

Mechanisms for maintaining constant Na+ delivery to the distal tubule (during euvolemia)

A
  • Autoregulation
  • Glomerular tubular balance
  • Sympathetic activity to maintain GFR and increase Na+ reabsorption in proximal tubule
  • Ang II to maintain GFR and increase Na+ reabsorption in proximal tubule
  • Local metabolites (prostaglandins, NO, dopamine) which try to maintain GFR
51
Q

Glomerular Tubular Balance

A

mechanism tries to maintain % of Na and water reabsorbed, particularly in the proximal tubule constant

no nerves or hormones involved

⇡ filtered load, ⇡ reabsorption to 60-65%

52
Q

Mechanisms for regulating Na+ reabsorption in the distal tubule and collecting duct

A

Aldosterone

ANP

ADH (minor function)

53
Q

ECF volume contraction → renal perfusion pressure is ___ → renal plasma flow is ___ → PGC is ___ → ___ in πGC → GFR is ___ → ____ salt and water excretion

A

ECF volume contraction → renal perfusion pressure is decreased → renal plasma flow is decreased → PGC is decreased → increase in πGC → GFR is decreased → decreased salt and water excretion

54
Q

ECF volume contraction → ___ renal sympathetic nerve activation → ___ constriction of renal arterioles → ___ GFR → __ salt and water excretion

A

ECF volume contraction → increased renal sympathetic nerve activation → increased constriction of renal arterioles → decreased GFR → decreased salt and water excretion

55
Q

ECF volume contraction → plasma oncotic pressure is ___ → directly ___ GFR→ __ salt and water excretion

A

ECF volume contraction → plasma oncotic pressure is increased → directly decreases GFR→ reduces salt and water excretion

56
Q

ECF volume contraction → ___ renal sympathetic nerve activation → ___ constriction of renal arterioles → ___ RBF more than GFR → Filtration Fraction ___ → __ reabsorption of NaCl in proximal tubule

A

ECF volume contraction → increased renal sympathetic nerve activation → increased constriction of renal arterioles → decreased RBF more than GFR → Filtration Fraction increased → increased reabsorption of NaCl in proximal tubule

57
Q

ECF volume contraction → ___ renal sympathetic nerve activation → __ NaCl reabsorption in proximal tubule

A

ECF volume contraction → increased renal sympathetic nerve activation → increased NaCl reabsorption in proximal tubule

58
Q

ECF volume contraction → ___ renin secretion (through various mechanisms) → ___ plasma Ang II → ___ GFR → __ salt and water excretion

A

ECF volume contraction → increased renin secretion (through various mechanisms) → increased plasma Ang II → decreased GFR → decreased salt and water excretion

59
Q

ECF volume contraction → ___ renin secretion (through various mechanisms) → ___ plasma Ang II → ___ RBF more than GFR → Filtration Fraction ___ → __ salt and water reabsorption in proximal tubule

A

ECF volume contraction → increased renin secretion (through various mechanisms) → increased plasma Ang II → decreased RBF more than GFR → Filtration Fraction increases → increased salt and water reabsorption in proximal tubule

60
Q

ECF volume contraction → ___ renin secretion (through various mechanisms) → ___ plasma Ang II → ___ Na reabsorption through Na/H+ antiporter in proximal tubule

A

ECF volume contraction → increased renin secretion (through various mechanisms) → increased plasma Ang II → increased Na reabsorption through Na/H+ antiporter in proximal tubule

61
Q

ECF volume contraction → ___ renin secretion (through various mechanisms) → ___ plasma Ang II → ___ aldosterone secretion → ___ Na reabsorption in late distal and collecting ducts

A

ECF volume contraction → increased renin secretion (through various mechanisms) → increased plasma Ang II → increased aldosterone secretion → increased Na reabsorption in late distal and collecting ducts

62
Q

ECF volume contraction → ___ ADH plasma levels → ___ water reabsorption in collecting tubule

A

ECF volume contraction → increased ADH plasma levels → increased water reabsorption in collecting tubule

63
Q

ECF volume contraction → ___ stretch of atria walls → ___ ANP secretion → ___ ANP mediated natriuresis

A

ECF volume contraction → decreased stretch of atria walls → decreased ANP secretion → decreased ANP mediated natriuresis

64
Q

What happens to volume contraction or expansion during pathological conditions?

A

local and autoregulatory mechanisms are “overridden” by the neurohumoral compensatory mechanisms which are activated

65
Q

Congestive Heart Failure

A

Patient with failing heart → kidneys try to compensate for heart failure → increases heart failure

Patient with failing heart → decreased CO → decreased renal perfusion pressures → decreased GFR → increased activity of renin-angiotensin-aldosterone system and renal sympathetic nerves → increased sodium retention even when patient is in positive sodium balance → causes edema

66
Q

Neurohumoral compensatory pathways

A
  • sympathetic nervous stimulation
  • activation of renin-angiotensin system
  • increase ADH release
  • increase aldosterone

pathways lead to greater salt and water retention which exacerbates edema

67
Q

Hyponatremia

A

plasma Na+ concentration of less than 135 mEq/L w/ osmolarity to < 275 mOsm/L

too much water

⇡ ADH release → ⇡ H2O reabsorption → causes hyponatremia

usually occurs in heart failure b/c you’re absorbing more water than Na

68
Q

Most common cause of hyponatremia is…

A

dysregulation of ADH secretion → “syndrome of inappropriate ADH secretion (SIADH)”

increased ADH release from posterior pituitary → results in high levels of water reabsorption from the collecting duct and hyponatremia (too much water)

69
Q

Hypernatremia

A

plasma Na+ concentration > 145 mEq/L w/ osmolarity to > 295 mOsm/L

ADH dysregulation

70
Q

Causes of hypernatremia

A
  • decreased ADH release from posterior pituitary → causes massive output of hypoosmotic urine and hypernatremia
  • Plasma ADH is relatively normal → tubule response to circulating hormone is severely depressed → increased hypoosmotic urinary output → hypernatremia
71
Q

ECF volume expansion → renal perfusion pressure is ___ → renal plasma flow is ___ → PGC is ___ → ___ in πGC → GFR is ___ → ____ salt and water excretion

A

ECF volume expansion → renal perfusion pressure is increased → renal plasma flow is increased → PGC is increased → decrease in πGC → GFR is increased → increased salt and water excretion

72
Q

ECF volume expansion → ___ renal sympathetic nerve activation → ___ constriction of renal arterioles → ___ GFR → __ salt and water excretion

A

ECF volume expansion → decreased renal sympathetic nerve activation → decreased constriction of renal arterioles → increased GFR → increased salt and water excretion

73
Q

ECF volume expansion → plasma oncotic pressure is ___ → directly ___ GFR→ __ salt and water excretion

A

ECF volume contraction → plasma oncotic pressure is decreased → directly increases GFR→ increase in salt and water excretion

74
Q

ECF volume expansion → ___ renal sympathetic nerve activation → ___ constriction of renal arterioles → ___ RBF more than GFR → Filtration Fraction ___ → __ reabsorption of NaCl in proximal tubule

A

ECF volume expansion → decreased renal sympathetic nerve activation → decreased constriction of renal arterioles → increased RBF more than GFR → Filtration Fraction decreases → decreased reabsorption of NaCl in proximal tubule

75
Q

ECF volume expansion → ___ renal sympathetic nerve activation → __ NaCl reabsorption in proximal tubule

A

ECF volume expansion → decreased renal sympathetic nerve activation → decreased NaCl reabsorption in proximal tubule

76
Q

ECF volume expansion → ___ renin secretion (through various mechanisms) → ___ plasma Ang II → ___ GFR → __ salt and water excretion

A

ECF volume expansion → decreased renin secretion (through various mechanisms) → decreased plasma Ang II → increased GFR → decreased salt and water excretion

77
Q

ECF volume expansion → ___ renin secretion (through various mechanisms) → ___ plasma Ang II → ___ RBF more than GFR → Filtration Fraction ___ → __ salt and water reabsorption in proximal tubule

A

ECF volume expansion → decreased renin secretion (through various mechanisms) → decreased plasma Ang II → increased RBF more than GFR → Filtration Fraction decreases → decreased salt and water reabsorption in proximal tubule

78
Q

ECF volume expansion → ___ renin secretion (through various mechanisms) → ___ plasma Ang II → ___ Na reabsorption through Na/H+ antiporter in proximal tubule

A

ECF volume expansion → decreased renin secretion (through various mechanisms) → decreased plasma Ang II → decreased Na reabsorption through Na/H+ antiporter in proximal tubule

79
Q

ECF volume expansion → ___ renin secretion (through various mechanisms) → ___ plasma Ang II → ___ aldosterone secretion → ___ Na reabsorption in late distal and collecting ducts

A

ECF volume expansion → decreased renin secretion (through various mechanisms) → decreased plasma Ang II → decreased aldosterone secretion → decreased Na reabsorption in late distal and collecting ducts

80
Q

ECF volume expansion → ___ ADH plasma levels → ___ water reabsorption in collecting tubule → __ water excretion

A

ECF volume expansion → decreased ADH plasma levels → decreased water reabsorption in collecting tubule → increased water excretion

81
Q

ECF volume expansion → ___ stretch of atria walls → ___ ANP secretion → ___ ANP mediated natriuresis

A

ECF volume expansion → increased stretch of atria walls → increased ANP secretion → increased ANP mediated natriuresis

82
Q

Congestive Heart Failure Map

A

Systems Phys 2022 (25 decks)

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