Renal Physiology Review

Question 1

Fluid components highest in ECF

Answer 1

Na+
Cl-
HCO3-
Ca2+ (slightly)

Question 2

Fluid components highest in ICF

Answer 2

K+
Organic anions
Protein
Mg2+

Question 3

Protein levels are highest in the ____ and ____ compartments; membranes are impermeable to proteins so they don’t normally impact osmolarity but do exert _______ pressure

Answer 3

ICF; vascular; oncotic

Question 4

Indicators used to measure TBW, ECF, and Plasma Volume

Answer 4

TBW = 3H2O, 2H2O, antipyrine

ECF = 22Na, 125-iothalamate, thiosulfate, INULIN

Plasma volume = 125I-albumin, Evans blue dye [albumin can be used because it should not cross PMs]

Question 5

ICF and ISF are not measured directly. How are they calculated?

Answer 5

ICF = TBW - ECF

ISF = ECF - plasma

Question 6

ECF osmolality is driven (primarily) by ___ and ____

ICF osmolality is primarily driven by _____

Answer 6

Na+; Cl-

K+

Question 7

ICF, ECF, and osmolality changes with diarrhea, vomiting, or hemorrhage

Answer 7

ECF volume: decreases

ICF volume: no change

Osmolality: no change

[isosmotic volume contraction]

Question 8

ICF, ECF, and osmolality changes with dehydration

Answer 8

Depends on the cause!

Isosmotic dehydration caused by hemorrhage, burns, vomiting, diarrhea, hemorrhage — ECF decreases, no change in ICF or osmolality

Hyperosmotic dehydration caused by decreased fluid intake, diabetes insipidus, diabetes mellitus, fever — ECF decreases, ICF decreases, osmolality increases

Hyposmotic dehydration caused by adrenal insufficiency (e.g., Addison’s disease) — ECF decreases, ICF increases, ECF osmolarity decreases

Question 9

ICF, ECF, and ECF osmolarity changes with diabetes insipidus

Answer 9

ECF volume: decreases

ICF volume: decreases

ECF osmolarity: increases

Question 10

ICF, ECF, and ECF osmolarity changes with hypoaldosteronism

Answer 10

ECF volume: decreases

ICF volume: increases

ECF osmolarity: decreases

Question 11

ICF, ECF, and osmolality changes with diabetes mellitus

Answer 11

ECF volume decreases

ICF volume decreases

ECF osmolarity increases

Question 12

ICF, ECF, and ECF osmolarity changes with SIADH

Answer 12

ECF volume: increases

ICF volume: increases

ECF osmolarity: decreases

Question 13

What happens to RBCs placed in isotonic, hypotonic, and hypertonic solutions?

Answer 13

RBC in isotonic = no change

RBC in hypotonic = cell swells

RBC in hypertonic = cell shrinks

Question 14

Acute and chronic changes in renal blood flow and GFR caused by increased angiotensin II synthesis

Answer 14

RBF decreases

GFR increases

Question 15

Acute and chronic changes in renal blood flow and GFR caused by increased release of ANP

Answer 15

RBF: increases
GFR: increases

Question 16

Acute and chronic changes in renal blood flow and GFR caused by decreased prostaglandin formation

Answer 16

RBF: decreases
GFR: no change/decreases?

Question 17

Effect of sympathetic stimulation on RBF, GFR, renin secretion, and proximal tubular Na+ reabsorption

Answer 17

RBF: decreases
GFR: decreases

Renin secretion: increases

Proximal tubular Na+ reabsorption: increases [less is excreted]

Question 18

List factors that regulate secretion of aldosterone

Answer 18

Renin
Angiotensin II (increases aldosterone secretion)

Question 19

Physiological effects of RAAS [actions of aldosterone]

Answer 19

Increases Na+ reabsorption
Increases K+ secretion
Increases H+ secretion

Question 20

Effects of sympathetic nerves on regulation of Na+ reabsorption along the nephron

Answer 20

Sympathetics nerve stimulation —> increased NaCl reabsorption at PT, TAL, and DT/CD [PT most important site of action]

Question 21

Alterations in Na+ reabsorption with hypovolemia

Answer 21

Integrated response to decreased ECV:

GFR decreases —> increased Na+ reabsorption by proximal tubule, loop of henle, distal tubule, and collecting duct

Water reabsorption is enhanced

Question 22

Alterations in Na+ reabsorption with hypervolemia

Answer 22

Integrated response involves:

Increase in GFR —> decreased reabsorption of Na in proximal tubule, loop of henle, distal tubule, and collecting duct

Water excretion follows

Question 23

Effect of angiotensin II on regulation of Na+ reabsorption along the nephron

Answer 23

Angiotensin II —> increased NaCl reabsorption at PT, TAL, DT/CD

Question 24

Effect of aldosterone on regulation of Na+ reabsorption along the nephron

Answer 24

Aldosterone —> increased NaCl reabsorption at TAL, DT/CD

Question 25

Effect of ANP on regulation of Na+ reabsorption along the nephron

Answer 25

ANP —> decreased NaCl reabsorption at CD

Question 26

What change in fluid balance would you expect if you ate a high NaCl diet for 2 weeks?

Answer 26

ECF/Interstitial fluid volume increases [same effect as hyperaldosteronism aka Conn’s dz]

Question 27

A decrease in the GFR, RBF, and peritubular capillary hydrostatic pressure indicates constriction of the afferent arteriole. If there was also a rise in oncotic pressure in the peritubular capillary, it is an indication that the filtration fraction has increased. What does this mean for constriction vs. dilation of the efferent arteriole?

Answer 27

The efferent arteriole is constricted [plasma flow dropped more than the GFR indicating the efferent arteriole also vasoconstricted]

Question 28

With diabetes insipidus, there is ______ free water clearance and excretion of _____ is elevated

Answer 28

Positive [dilute urine]; potassium [d/t elevated aldosterone]

Question 29

Changes in sympathetic tone, plasma angiotensin II levels, ANP levels, and plasma oncotic pressure as a result of dehydration d/t severe diarrhea

Answer 29

Sympathetic tone increases Plasma angiotensin II levels increases ANP levels decreases Plasma oncotic pressure increases

Question 30

Changes in aldosterone, ANP/BNP, angiotensin II, and ADH levels with CHF

Answer 30

Aldosterone levels increase ANP-BNP levels increase Angiotensin II levels increase ADH levels increase

Question 31

What changes in TBW, ECF osmolarity, ECF volume, ICF osmolarity, and ICF volume would take place if a dehydrated individual replaced all their fluids with pure electrolyte-free water?

Answer 31

``` TBW: no change ECF osmolarity decreases ECF volume decrease ICF osmolarity decrease ICF volume increase ```