BRS Phys Review

Question 1

Total body water is approximately ____ of body weight

Answer 1

60%

Question 2

When is the percentage of total body water at its highest and and its lowest?

Answer 2

Highest in newborns and adult males

Lowest in adult females and adults with large amounts of adipose tissue

Question 3

What is the 60-40-20 rule for the distribution of body fluids?

Answer 3

TBW = 60% of body weight

ICF = 40% of body weight

ECF = 20% of body weight

Question 4

How much of your total body water is made up of ICF?

Answer 4

2/3

Question 5

What are the major cations and anions of ICF?

Answer 5

Major cations: K+ and Mg+

Major anions: protein and organic phosphates (ATP, ADP, AMP)

Question 6

How much of your total body water is made up of ECF?

Answer 6

1/3

Question 7

Describe the composition of ECF as well as its major cations and anions

Answer 7

Composed of interstitial fluid and plasma

Major cation: Na+

Major anion: Cl- and HCO3-

Question 8

________ makes up 1/4 of the ECF. What are the 2 major proteins?

Answer 8

Plasma (thus it is 1/12 of TBW)

Major plasma proteins: albumin and globulins

Question 9

If plasma makes up 1/4 of the ECF, what makes up the other 3/4?

Answer 9

Interstitial fluid (makes up 1/4 of TBW)

Question 10

Describe the composition of interstitial fluid

Answer 10

Same as that of plasma except that it has little protein; thus it is considered an ultrafiltrate of plasma

Question 11

Volumes of fluid compartments can be measured using a dilution method - in which a known amount of substance is given whose volume of distribution is the body fluid compartment of interest.

What substances are used as indicators for total body water?

Answer 11

Tritiated water
D2O
Antipyrene

Question 12

Volumes of fluid compartments can be measured using a dilution method - in which a known amount of substance is given whose volume of distribution is the body fluid compartment of interest.

The substance is allowed to _______. The __________ of the substance is measured in plasma.

Answer 12

Equilibrate; concentration

Question 13

Volumes of fluid compartments can be measured using a dilution method - in which a known amount of substance is given whose volume of distribution is the body fluid compartment of interest.

The substance is allowed to equilibrate. The concentration of the substance is measured in plasma.

How is the volume of distribution calculated based on this info?

Answer 13

Volume = amount/concentration

Question 14

Volumes of fluid compartments can be measured using a dilution method - in which a known amount of substance is given whose volume of distribution is the body fluid compartment of interest.

What substances are used as indicators for ECF?

Answer 14

Sulfate
Insulin
Mannitol

Question 15

Volumes of fluid compartments can be measured using a dilution method - in which a known amount of substance is given whose volume of distribution is the body fluid compartment of interest.

What substances are used as indicators for plasma?

Answer 15

Radioiodinated serum albumin (RISA)

Evans blue

Question 16

Volumes of fluid compartments can be measured using a dilution method - in which a known amount of substance is given whose volume of distribution is the body fluid compartment of interest.

What substances are used as indicators for interstitial fluid compartments?

Answer 16

Interstitial fluid compartments are measured indirectly!

Interstitial fluid volume = ECF volume - plasma volume

Question 17

Volumes of fluid compartments can be measured using a dilution method - in which a known amount of substance is given whose volume of distribution is the body fluid compartment of interest.

What substances are used as indicators for ICF?

Answer 17

ICF is measured indirectly!

ICF volume = TBW - ECF volume

Question 18

At steady state, ECF osmolarity and ICF osmolarity are _______. To achieve this, ______ shifts between the ECF and ICF compartments.

Answer 18

Equal; water

Question 19

What effect would infusion of an isotonic fluid, such as NaCl, have on ECF volume, ICF volume, ECF osmolarity, and Hct and serum [Na+]?

Answer 19

ECF volume increases –> BP increases

ICF volume unchanged

ECF osmolarity unchanged

Hct decreases, [Na+] unchanged

Question 20

Infusion of an isotonic fluid, such as NaCl, is also called _________

Answer 20

Isosmotic volume expansion

Question 21

What effect would loss of an isotonic fluid, which occurs with diarrhea, have on ECF volume, ICF volume, ECF osmolarity, Hct and serum [Na+]?

Answer 21

ECF vol decreases –> BP decreases

ICF vol unchanged

ECF osmolarity unchanged

Increased Hct, no change in [Na+]

Question 22

Loss of isotonic fluid, such as with diarrhea, is also called _______

Answer 22

Isosmotic volume contraction

Question 23

What effect would excessive NaCl intake have on ECF volume, ICF volume, ECF osmolarity, Hct and serum [Na+]?

Answer 23

ECF increases

ICF decreases

ECF osmolarity increases

Hct decreases

[Na+] increases

Question 24

Excessive NaCl intake is also called what?

Answer 24

Hyperosmotic volume expansion

Question 25

What are some key examples of hyperosmotic volume contraction?

Answer 25

Sweating Fever Diabetes insipidus

Question 26

What effect would hyperosmotic volume contraction have on ECF volume, ICF volume, ECF osmolarity, and serum [Na+]?

Answer 26

ECF volume decreases ICF volume decreases ECF osmolarity increases [Na+] increases

Question 27

What is the key example of Hyposmotic volume expansion?

Answer 27

SIADH [Syndrome of Inappropriate ADH] - resulting in gain of water

Question 28

What effect would hyposmotic volume expansion have on ECF volume, ICF volume, ECF osmolarity, and serum [Na+]?

Answer 28

ECF increases ICF increases ECF osmolarity decreases [Na+] decreases

Question 29

Adrenal insufficency is a key example of what type of volume change in body fluids?

Answer 29

Hyposmotic volume contraction (adrenocortical insufficiency = loss of NaCl)

Question 30

What effect would hyposmotic volume contraction have on ECF volume, ICF volume, ECF osmolarity, Hct and serum [Na+]?

Answer 30

ECF volume decreases ICF volume increases ECF osmolarity decreases Increase in Hct Decrease in [Na+]

Question 31

The clearance equation indicates the volume of plasma cleared of a substance per unit time

Answer 31

C = UV/P Where U is urine concentration, V is urine volume/time, P is plasma concentration

Question 32

Renal blood flow is _____% of cardiac output and is _______ proportional to pressure difference between the renal artery and renal vein It is _____ proportional to the resistance of the renal vasculature

Answer 32

25; directly Indirectly

Question 33

_________ of renal arterioles, which leads to a decrease in RBF, is produced by activation of the ______ nervous system and angiotensin II. At low concentrations, angiotensin II preferentially constricts ________ arterioles, thereby "protecting" (increasing) the GFR

Answer 33

Vasoconstriction; sympathetic Efferent

Question 34

At low concentrations, angiotensin II constricts efferent arterioles, thus protecting/increasing GFR. What type of drug dilates efferent arterioles and produces a decrease in GFR, thus reducing hyperfiltration and occurance of diabetic nephropathy in diabetes mellitus?

Answer 34

ACE inhibitors (angiotensin-converting enzyme)

Question 35

How is autoregulation of RBF accomplished?

Answer 35

By changing renal vascular resistance. If arterial pressure changes, a proportional change occurs in renal vascular resistance to maintain a constant RBF

Question 36

Autoregulation of RBF keeps it constant over the range of arterial pressures from ____ to _____ mm Hg

Answer 36

80-200

Question 37

What are the 2 mechanisms for RBF autoregulation?

Answer 37

Myogenic mechanism Tubuloglomerular feedback

Question 38

What is the myogenic mechanism for autoregulation of RBF?

Answer 38

Renal afferent arterioles contract in response to stretch. Thus, increased renal arterial pressure stretches the arterioles, which contract and increase resistance to maintain constant blood flow

Question 39

What is the tubuloglomerular feedback mechanism for autoregulation of RBF?

Answer 39

Increased renal arterial pressure leads to increased delivery of fluid to the macula densa which senses the increased load and causes constriction of the nearby afferent arteriole, increasing resistance to maintain constant blood flow

Question 40

Renal plasma flow is measured by the degree of clearance (filtration and secretion) of what substance?

Answer 40

Para-aminohippuric acid (PAH)

Question 41

Clearance of PAH measures effective renal plasma flow (RPF), and underestimates true RPF by ____%. Why is this?

Answer 41

10% Clearance of PAH does not measure RPF to regions of the kidney that do not filter and secrete PAH

Question 42

How is RPF calculated?

Answer 42

RPF = C[PAH] = (U[PAH] x V)/P[PAH] Where U[PAH] is PAH in urine, V is urine flow rate, and P[PAH] is plasma PAH

Question 43

How is RBF calculated?

Answer 43

RBF = RPF/1-Hct Note that denominator is fraction of BV occupied by plasma

Question 44

Measurement of GFR can be measured by the degree of clearance of what substance?

Answer 44

Inulin

Question 45

How is GFR calculated?

Answer 45

GFR = ([U]inulin x V)/[P]inulin

Question 46

Both BUN and serum creatinine increase when GFR _________

Answer 46

Decreases

Question 47

What happens to BUN and serum creatinine in prerenal azotemia (hypovolemia)?

Answer 47

BUN increases more than serum creatinine and there is an increased BUN/creatinine ratio

Question 48

What happens to GFR with age? Does this affect serum creatinine?

Answer 48

GFR decreases with age, although serum creatinine remains constant because of decreased muscle mass

Question 49

What is the filtration fraction? How is it calculated?

Answer 49

Fraction of RPF filtered across the glomerular capillaries Filtration fraction = GFR/RPF

Question 50

What is the normal filtration fraction?

Answer 50

About 0.20. Thus 20% of the RPF is filtered; the remaining 80% leaves the glomerular capillares by the afferent arterioles and becomes the peritubular capillary circulation

Question 51

What is the result of an increased filtration fraction?

Answer 51

Increases in the protein concentration of peritubular capillary blood --> increased reabsorption in the PCT

Question 52

What is the result of a decreased filtration fraction?

Answer 52

Decreases in the protein concentration of peritubular capillary blood and decreased reabsorption in the PCT

Question 53

What is the driving force for glomerular filtration?

Answer 53

Net ultrafiltration pressure across the glomerular capillaries

Question 54

T/F: filtration is always favored in glomerular capillaries

Answer 54

True; because the net ultrafiltration pressure always favors the movement of fluid out of the capillary

Question 55

How can GFR be expressed by the Starling equation?

Answer 55

GFR = Kf[(Pgc-Pbs)-(PIgc-PIbs)

Question 56

Describe the glomerular barrier

Answer 56

Consists of capillary endothelium, basement membrane, and filtration slits of the podocytes

Question 57

What lines the glomerular barrier, restricting filtration of plasma proteins?

Answer 57

Anionic glycoproteins (restrict filtration since plasma proteins are also negatively charged) In glomerular disease, the anionic charges on the barrier may be removed, resulting in proteinuria

Question 58

Pgc is the glomerular capillary hydrostatic pressure, which is constant along the length of the capillary. What increases Pgc?

Answer 58

Dilation of afferent arterioles or constriction of the efferent arterioles, which then increase net ultrafiltration pressure and GFR

Question 59

Pi(gc) is glomerular capillary oncotic pressure. It normally _______ along the length of the glomerular capillary

Answer 59

Increases; because filtration of water increases the protein concentration of glomerular capillary blood

Question 60

Glomerular capillary oncotic pressure is ________ by increases in protein concentration. Increases in Pi(gc) cause _________ in net ultrafiltration pressure and GFR

Answer 60

Increased; decreases

Question 61

pi(bs) is bowman's space oncotic pressure. It is usually ____

Answer 61

Zero; therefore it is ignored because only a small amount of protein is normally filtered

Question 62

Changes in GFR, RPF, and/or filtration fraction from: Constriction of afferent arterioles (sympathetic activity)

Answer 62

GFR decreases (caused by decreased PGC) RPF decreases Filtration fraction: No change

Question 63

Changes in GFR, RPF, and/or filtration fraction from: Angiotensin II

Answer 63

Angiotensin II preferentiall constricts efferent arteriole - so: GFR increases (caused by increase in PGC) RPF decreases Filtration fraction increases

Question 64

Changes in GFR, RPF, and/or filtration fraction from: Increased plasma protein concentration

Answer 64

GFR decrease (caused by increased Pi(GC)) RPF: no change Filtration fraction decreases

Question 65

Changes in GFR, RPF, and/or filtration fraction from: Urethral stone

Answer 65

GFR decrease (caused by increased PBS) RPF: no change Filtration fraction: decrease

Question 66

Reabsorption and secretion

Answer 66

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