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Medical Physiology > Test 4 Lecture 2 > Flashcards

Test 4 Lecture 2 Flashcards

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USMLE® Step 1 flashcards
1
Q

Water accounts for how much of body weight?

A

50-70% (average 60%)

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2
Q

What causes variations in total body water?

A

Gender and amount of adipose tissue

correlates INVERSELY with fat, and women have lower water content, thin men have highest, fat women have lowest

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3
Q

How much of total body weight is ECF and ICF?

A 
ICF = two thirds of total body water (40% of body weight)
ECF = one third  of total body water (20% of body weight)
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4
Q

What are the divisions within the ECF?

A

3/4 of ECF is in interstitial fluid (16%)

1/4 of ECF is in plasma (4%)

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5
Q

Composition of ICF

A 
Cations = K, Mg
Anions = proteins, organic phosphates like ATP, ADP, AMP
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6
Q

What is plasma?

A

the fluid the circulates in the blood vessels

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7
Q

What is interstitial fluid?

A

bathes the cells

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8
Q

Composition of ECF

A 
Cation = Na
Anion = CL and HCO3
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9
Q

What is the composition of blood volume?

A

55% plasma (93% plasma water, 7% plasma proteins), 45% blood cells (hematocrit, higher in males than females)

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10
Q

Gibbs-Donnan Effect

A

predicts that plasma will have a slightly higher concentration of small cations than ISF and slightly lower concentration of small anions

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11
Q

What are the 4 steps for measuring volumes of body fluid compartments by the dilution method?

A

1) Identify an appropriate marker
2) Injection of a known amount of the marker substance
3) Equilibration and measurement of plasma concentration
4) Calculation of the volume of the body fluid comparment

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12
Q

What is the marker for total body water?

A

D20, THO, antipyrine

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13
Q

What is the marker for ECF?

A

Sulfate, mannitol, inulin

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14
Q

What is the marker for ICF?

A

TBW - ECF

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15
Q

What is the marker for plasma?

A

RISA, Evan’s Blue

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16
Q

What is the marker for ISF?

A

ECF - plasma

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17
Q

The volume of a body fluid compartment depends on the amount of _________ it contains.

A

solute (example, ECF volume is determined by amount of NaCl and NaHCO3 it contains)

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18
Q

Osmolarity is the concentration of ____________.

A

Osmotically active particles

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19
Q

Volume contraction means a ______ in ______ volume.

A

decrease, ECF

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20
Q

Volume expansion means an ______ in ______ volume.

A

increase, ECF

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21
Q

What is clearance?

A

General concept that describes the rate at which substances are removed from plasma

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22
Q

Renal clearance is the ratio between ______ to ______.

A

Urinary excretion to plasma concentration

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23
Q

What is the clearance for albumin?

A

zero (not filtered across glomerular capillaries)

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24
Q

What is the clearance for glucose?

A

zero (filtered then reabsorbed)

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25
Q

What is the clearance for Na, urea, phosphate and Cl?

A

higher than zero, they are filtered and then partially reabsorbed

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26
Q

What is the clearance for para-amniohippuric acid?

A

highest clearance, filtered and secreted

27
Q

What is the clearance for inulin?

A

clearance measures the glomerular filtration rate (freely moves across glomerular capillaries, but neither reabsorbed or secreted)

28
Q

Cx/Cinulin = 1

A

also a glomerular marker

29
Q

Cx/Cinulin = < 1

A

clearance of x is lower than inulin, either the substance is not filtered OR filtered and then reabsorbed (albumin, glucose, NA, urea, phosphate, Cl)

30
Q

Cx/Cinulin = > 1

A

clearance of x is higher than inulin, substance is filtered and secreted (organic acids and bases, sometimes K)

31
Q

How much CO do the kidneys receive?

A

25% (1.25 L/min)

32
Q

RBF is ______ proportional to the pressure gradient between the renal artery and vein.

A

Directly

33
Q

RBF is _______ proportional to the resistance of the renal vasculature.

A

Inversely

34
Q

What are the vasoconstrictors for RBF?

A

Sympathetic nerves (catecholamines), Angiotensin II, Endothelin

35
Q

What are the vasodilators for RBF?

A

PGE2, PGI2, Nitric Oxide, Bradykinin, Dopamine

36
Q

RAP can vary from ____ to ____ without a change to RBF.

A

80 to 200 mmHg

37
Q

Resistance is controlled primarily by ________ arterioles in renal autoregulation.

A

Afferent

38
Q

ANS is involved in renal autoregulation. (T/F)

A

False, denervated kidney transplants autoregulate

39
Q

What are the 2 hypothesis for autoregulation of RBF?

A

Myogenic hypothesis and tubuloglomerular feeback

40
Q

Explain the mechanism by which the myogenic hypothesis works.

A

Increases in RAP stretch the walls of afferent arterioles, which then contract. Contraction leads to increased resistance. Increased resistance balances increased pressure, RBF stays constant.

41
Q

What are the unanswered questions with the tubuloglumerular feedback mechanism?

A

1) What component of the tubular fluid is sensed at the macula densa? (could be Na, Cl, Ca, osmolarity)
2) What vasoactive substance is secreted by the juxtaglomerular apparatus to act locally on the afferent arterioles? (could be adenosine, prostaglandins, kinins)

42
Q

Renal plasma flow (RPF) can be estimated by clearance of ______.

A

organic acid PAH

43
Q

Renal blood flow can be calculated by _______.

A

RPF and hematocrit

44
Q

What is the fluid that is filtered into Bowman’s space?

A

ultrafiltrate

45
Q

What is ultrafiltrate made up of?

A

water and small solutes of blood (DOES NOT contain blood cells, or proteins)

46
Q

What are the forces responsible for glomerular filtration?

A

Starling Forces

47
Q

What can pass through the endothelium? What cannot?

A

Fluid, dissolved solutes, and plasma proteins can filter through. Blood cells cannot.

48
Q

What are the 3 layers of the basement membrane?

A 
Lamina rara interna (fused to the endothelium)
Lamina densa (middle)
Lamina rara externa (fused to epithelial cell layer)
49
Q

The basement membrane permits filtration of plasma proteins. T/F

A

False, does not, is the most significant barrier of the glomerular capillary

50
Q

Where are the negative charges present?

A

Endothelium, lamina rar interna and externa, podocytes and food processes, and on the filtration slits of the epithelium

51
Q

What is the consequence of the negatively charged barrier?

A

Provides an electrostatic component to filtration, negatively charged solute will be repelled from the barrier (does not apply to small solutes like Na, K, Cl or HCO3)

52
Q

What causes proteinuria?

A

A removal of the negative charges on the barrier, which allows an increased filtration of plasma proteins

53
Q

Which of the Starling forces is equal to zero?

A

ISF oncotic pressure

54
Q

What two factors contribute to Kf (filtration coefficient)?

A

water permeability per unit of surface area

total surface area

55
Q

How does Pgc (hydrostatic pressure in the glomerular capillaries) vary from system pressure?

A

Relatively higher and pressure (45 mmHg) does not fall along the length of the capillary

56
Q

What role does Pbs (hydrostatic pressure in bowman’s space) play?

A

Force opposing filtration, origin if the fluid present in the lumen of the nephron (10 mmHg)

57
Q

Which way does net ultrafiltration pressure favor?

A

always favors filtration so that the direction of fluid movement is out of the capillaries

58
Q

Which starling pressure changed to make net ultrafiltration zero?

A

oncotic pressure of glomerular capillary blood

59
Q

What are the 3 characteristics of a glomerular marker?

A

1) must be freely filtered across the glomerular capillaries with no size/charge restrictions
2) cannot be reabsorbed or secreted by renal tubule
3) when infused, cannot alter the GFR

60
Q

Hypoxemia

A

decrease in arterial PO2

61
Q

Hypoxia

A

decrease in O2 delivery to the tissues

62
Q

What are some causes of hypoxemia?

A

High altitude, hypoventiliation, diffusion defect, V/Q defect, right-to-left shunt

63
Q

What is the A-a gradient?

A

The difference between the PO2 of alveolar gas and the PO2 of systemic arterial blood

64
Q

What are some causes of hypoxia?

A

Decreased CO, hypoxemia, anemia, Carbon monoxide poisoning, cyanide poisoning

Medical Physiology (4 decks)

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