Renal IIIa

Question 1

Maintenance of body fluid is tied to….

Answer 1

regulation of body sodium content

Question 2

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

Answer 2

most body Na is retained within ECF

most body K+ is intracellular

Question 3

Any net increase in total body fluid….

Answer 3

is retained in the ECF and body fluid volume increases

Question 4

Any net loss of total body Na results in…

Answer 4

decrease in ECF volume

Question 5

___ is critical in the maintenance of body fluid volume

Answer 5

Regulation of body Na

Question 6

Increase Na → __ osmolarity → __ H₂O

Answer 6

Increase Na → increases osmolarity → increases H₂O

Question 7

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 __

Answer 7

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

Question 8

Sodium Excretion Equation

Answer 8

Sodium Excretion = Sodium Filtered - Sodium Reabsorbed

= (GFR X P_Na) - Sodium reabsorbed

P_Na = plasma concentration of Na

Question 9

It is possible to adjust sodium excretion by…

Answer 9

controlling plasma sodium, GFR, and sodium reabsorption

Question 10

What regulates GFR and sodium reabsorption?

Answer 10

the kidneys

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

Question 11

Changes in Plasma Sodium

Answer 11

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

Question 12

A person is considered in positive Na balance if…

Answer 12

excretion is less than Na ingested

retaining water

Question 13

A person is in negative Na balance when…

Answer 13

Na excretion is more than Na ingested

net excreting fluid

Question 14

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

Answer 14

• 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

Question 15

Extrinsic control of GFR:

Answer 15

• Renal sympathetic nerves
• Renin-angiotensin system

Question 16

Extrinsic control of GFR: Renal Sympathetic nerves

Answer 16

• increased renal sympathetic nerve activation → increased renal arteriolar constriction → decreased P_GC → decreased GFR
• Increases renal sympathetic nerve activation → increased renal arteriolar constriction → decreased renal blood flow → increased average π_GC → decreased GFR

Question 17

Extrinsic control of GFR: Renin-Angiotensin System

Answer 17

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

Question 18

Local and Direct regulation of GFR:

Answer 18

• Autoregulation
• Prostaglandins

Question 19

Local and Direct regulation of GFR: Autoregulation

Answer 19

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

Question 20

Local and Direct regulation of GFR: Prostaglandins

Answer 20

PGE₂ and PGI₂

vasodilators

help make sure too much constriction doesn’t occur

Question 21

Tubular Sodium Reabsorption is mediated by…

Answer 21

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

Question 22

Where is aldosterone produced?

Answer 22

the adrenal cortex

Question 23

How does aldosterone work?

Answer 23

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)

Question 24

3 Major Inputs to the adrenal gland stimulating aldosterone secretion…

Answer 24

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

increase any of these → increase aldosterone secretion

Question 25

Anything that increases Ang II, ___ aldosterone

Answer 25

increases

Question 26

Aldosterone acts in the ___ and ___ Na reabsorption

Answer 26

collecting duct; increases

Question 27

Control of aldosterone secretion

Answer 27

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

Question 28

Tubular effects of renal sympathetic nerves

Answer 28

• 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

Question 29

Increased constriction, ___ Filtration Fraction (FF)

Answer 29

increases

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

Question 30

Tubular effects of Ang II: Direct effects

Answer 30

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

Question 31

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

Answer 31

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

Question 32

Tubular effects of Ang II: Aldosterone

Answer 32

increase aldosterone secretion

Question 33

Tubular effects of Ang II: Ang II

Answer 33

Ang II has a profound effect on Na reabsorption by itself

Question 34

What secretes Atrial Natriuretic Peptide (ANP)?

Answer 34

Cardiac Atrial Cells

Question 35

How is ANP released?

Answer 35

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

Question 36

Atrial Natriuretic Peptide (ANP)

Answer 36

inhibits sodium reabsorption

increases Na excretion

Question 37

ADH (vasopressin)

Answer 37

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

Question 38

Water Excretion

Answer 38

Water excretion = volume filtered (GFR) - volume reabsorbed

Question 39

What is the main determinant of water excretion?

Answer 39

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

Question 40

Control of ADH secretion

Answer 40

baroreceptors and/or osmoreceptors

Question 41

What is the major function of ADH?

Answer 41

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

Question 42

Baroreceptor Control of ADH Secretion

Answer 42

⇣ 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

Question 43

Osmoreceptor Control of ADH Secretion

Answer 43

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

Question 44

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

Answer 44

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

Question 45

Thirst response

Answer 45

centers that mediate thirst are located in the hypothalamus

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

Question 46

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

Answer 46

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

Question 47

Effect of Ang II on thirst

Answer 47

Ang II stimulates thirst by a direct effect on the brain

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

Question 48

Define: Euvolemia

Answer 48

normal ECF volume

Question 49

Control of Renal NaCl excretion during Euvolemia

Answer 49

• 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

Question 50

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

Answer 50

• 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

Question 51

Glomerular Tubular Balance

Answer 51

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%

Question 52

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

Answer 52

Aldosterone

ANP

ADH (minor function)

Question 53

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

Answer 53

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

Question 54

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

Answer 54

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

Question 55

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

Answer 55

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

Question 56

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

Answer 56

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

Question 57

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

Answer 57

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

Question 58

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

Answer 58

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

Question 59

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

Answer 59

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

Question 60

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

Answer 60

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

Question 61

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

Answer 61

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

Question 62

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

Answer 62

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

Question 63

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

Answer 63

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

Question 64

What happens to volume contraction or expansion during pathological conditions?

Answer 64

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

Question 65

Congestive Heart Failure

Answer 65

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

Question 66

Neurohumoral compensatory pathways

Answer 66

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

pathways lead to greater salt and water retention which exacerbates edema

Question 67

Hyponatremia

Answer 67

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

Question 68

Most common cause of hyponatremia is…

Answer 68

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)

Question 69

Hypernatremia

Answer 69

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

ADH dysregulation

Question 70

Causes of hypernatremia

Answer 70

• 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

Question 71

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

Answer 71

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

Question 72

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

Answer 72

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

Question 73

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

Answer 73

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

Question 74

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

Answer 74

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

Question 75

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

Answer 75

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

Question 76

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

Answer 76

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

Question 77

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

Answer 77

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

Question 78

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

Answer 78

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

Question 79

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

Answer 79

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

Question 80

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

Answer 80

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

Question 81

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

Answer 81

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

Question 82

Congestive Heart Failure Map

Answer 82