PRIN Review Flashcards
1
Q
Total body water percent in 70kg male
A
60% water by mass (50% in females due to higher body fat)
2
Q
What two compartments make up total body water
A
Intracellular fluid (ICF) and extracellular fluid (ECF)
3
Q
How much of total body water is ICF? ECF?
A
ICF=2/3 TBW ECF=1/3 TBW
4
Q
How much of ECF is plasma? Interstitial fluid?
A
Plasma = 1/5 ECVF (5% TBW) Interstitial fluid = 4/5 ECFV (15% TBW)
5
Q
How do you calculate plasma volume from blood volume?
A
plasma volume = blood volume X (1-hematocrit)
6
Q
Main cation in ICF
A
K+
7
Q
Main anion in ICF
A
proteins, organic phosphates, others
8
Q
Main cation in plasma
A
Na+
9
Q
Main anions in plasma
A
Cl-, HCO3- (more Cl-)
10
Q
How much of plasma is water?
A
93%
11
Q
Main cation in interstitial fluid
A
Na+
12
Q
Main anion in interstitial fluid
A
Cl-, HCO3-
13
Q
Why is there less protein found in interstitial fluid than plasma?
A
Because proteins are non penetrating so more likely to be in plasma
14
Q
How do you calculate number of moles
A
mass/molecular weight=moles
15
Q
What are osmolarity and osmolality measuring?
A
Number of osmotically active particles dissolved in water–independent of molecular size and valence
16
Q
What is osmolarity
A
mosmol/L water
17
Q
What is osmolality
A
mosmol/Kg water –like to use this because not affected by temperature like volume can be
18
Q
How do the osmolalities of the major body fluid compartments compare normally
A
Osmolalities are all about equal–iso-osmotic
19
Q
What is normal osmolality
A
280-300 mosmol/kg
20
Q
What is the Gibbs-Donnan effect
A
proteins in plasma ( - charge) that can’t cross the membrane due to size result in increased cations in the plasma to compensate for the proteins’ negative charge—therefore ECF osmolality increases
21
Q
Penetrating solutes
A
can move across membrane and thus achieve equal osmolality so do not cause net movement of water
22
Q
Nonpenetrating solutes
A
CANT move across the membrane–“EFFECTIVE OSMOLES”–increased effective osmoles may cause net movement of water
23
Q
What is an effective osmole in the ECF
A
Na+ –tends to stay in the ECF–increase or decrease in [Na+] in ECF will induce H20 to move in or out of ECF
24
Q
What is an ineffective osmole example
A
Urea–CAN move across the membrane and thus doesnt change the osmotic gradient
25
What is tonicity
term used to describe effective osmolality of a solution ([effective osmoles])
26
Where does Na+ largely segregate
the ECF
27
How do you use Na+ to estimate Posm?
Posm = 2PNa+ (+10 to account for other solutes) (Plasma osmolarity= 2 salts and a sugar BUN//2Na+ glucose+urea)
28
What is osmotic pressure
the amount of pressure required to STOP the osmotic flow of water across a semi-permeable membrane
29
What is the osmotic pressure proportional to?
#particles dissolved/unit volume (NOT related to solute size or valence) Osmotic pressure = nRTC(phi) (phi)=osmotic coefficient n=#dissolved particles R=0.082 Latm/mol T=temp in Kelcin C=concentration of total solute in OSMOLES
30
What are Starling's Forces?
HYDROSTATIC and ONCOTIC pressures in the capillary and interstitum ---has to do with water and solute movement during filtration ---Jv=Kf [(Pc-Pi) - (∏c-∏i)] ---Pc = capillary hydrostatic pressure, Pi=interstitial hydrostatic pressure ---Capillary oncotic pressure is mainly exerted by proteins (Interstitial oncotic pressure can be approximated to zero) +Jv value means that water is forces out of the capillaries into the interstitium
31
What is the composition of the ultrafiltrate in the glomerulus compared to plasma
same composition as plasma but without large macromolecules like proteins
32
What is GFR
volume of plasma being filtered per unit time--starlings forces put into practice
33
What determines GFR
afferent/efferent arteriole vasodilation/constriction, as well as hydrostatic and oncotic pressures in the glomerulus
34
Clearance equation
Cx=(UxV)/Px where V = volume flow rate in mL/min
35
What is the urinary excretion rate
UxV = urinary excretion rate of X in mg/min
36
How is Creatinine used to estimate GFR? (equation)
Pcr X GFR = Ucr X V
37
What does the Cockcroft-Gault formula get used for?
accounts for age and body mass when calculating GFR
38
What is Puf?
Net filtration pressure (combination of Starlings forces--if get confused draw a capillary)
39
GFR =
Kf X Puf
40
How could you manipulate GFR?
change capillary permeability change capillary/diffusion/filter surface area change hydrostatic pressure gradient change oncotic pressure gradient
41
What is autoregulation/myogenic control of GFR
refers to effect of vasoconstriction/dilation changes on GFR (compensatory responses) blood flow = change in pressure/change in resistance As BP rises, GFR rises and hydrostatic pressure in the glomerulus increases --\> constrict afferent arteriole--\> decreases GFR to keep it at stable level Can also vasodilate afferent arteriole to increase GFR Vasoconstrict efferent to increase GFR Vasodilate efferent to lower GFR
42
What is tubuloglomerular feedback in the kidney?
point where thick ascending limb contacts its originating glomerulus to form the JUXTAGLOMERULAR APPARATUS (JGA)--\> contains MACULA DENSA, granular cells, extraglomerular mesangial cells Feedback through RAAS
43
How does the macula dense in the JGA participate in tubuloglomerular feedback in the kidney?
senses tubular flow rate and solute concentration when flow is high or solute concentration is high, macular dense sends signals that result in ATP and adenosine release which increases afferent arteriole CONSTRICTION/resistance when low flow rate or solute concentration is sensed--\>signals release of NO and prostaglandin release which decreases afferent arteriole constriction
44
Effect of angiotensin II on the filtration rate/GFR
will constrict both the efferent and afferent arterioles so the effect net will vary
45
Describe the neurohormonal control of GFR
through RAAS and sympathetic system
46
List 3 kidney functions
1. regulatory--ion composition, pH balance, body fluid volume, long term regulation of BP 2. endocrine--production and secretion of ERYTHROPOIETIN, activation of vitamin P, production and release of vasoactive substances i.e in RAAS/kinins/prostaglandins 3. Excretion--formation of urine and elimination of waste (urea, uric acid, creatinine)
47
Function of podocytes
attach capillary to Bowman's capsule and create filtration units
48
Path of filtrate in nephron
Proximal tubule --\> loop of Henle--\> distal tubule --\> Collecting Duct system
49
Where is the most important site for K+ balance in the nephron?
Distal nephron (the distal convoluted tubule and the collecting duct)
50
How do you regulate ECFV
regulate it indirectly via regulation of Na+ balance--\>where Na+ goes, volume will follow--\>ECFV kept constant by matching sodium excretion to sodium ingestion nonrenal mechanisms are neurohormonal and involve changes in vascular resistance and cardiac output
51
How do you regulate plasma osmolality
Na+ is regulated via water to keep Na+ homeostasis this is sacrificed to preserve ECFV only when severely volume depleted disturbances in Na+ lead to ADH secretion from posterior pituitary and activation of thirst mechanism--\>ADK can be stimulation by volume depletion, nausea/vomiting, pain, exercise and some medications
52
Where does ATII act in the nephron?
early proximal tubule--increases Na+ reabsorption and K+ excretion distal tubule--NaCl reabsorption
53
Where does the majority of Na+ reabsorption happen in the nephron?
late proximal tubule--65% Na+ reabsorbed here--FIXED
54
What percent of Na+ is not reabsorbed?
less than 1%
55
What part of the nephron is impermeable to H20?
Ascending limb of loop of Henle--Na is reabsorbed here
56
What part of the nephron is impermeable to Na+?
Descending limb of loop of Henle--H2O reabsorped here
57
How much Na+ is reabsorbed in the ascending limb of the loop of Henle?
25%
58
How much Na+ is reabsorbed in the distal tubule?
approx 5%--VARIABLE
59
Where does aldosterone act in the nephron?
Thick ascending limb of loop of Henle and distal tubule (and collecting duct) (NaCl reabsorption increase)
60
Which is usually preferentially maintained: volume or osmolality?
osmolality--exception is massive volume change if volume decreases by \>15%, will preferentially preserve volume; otherwise preserves osmolality
61
In a hypovolemic state, what is release? hypervolemic?
hypovolemic state--\>release ADH to retain water hypervolemic state--\>stop ADH to excrete water
62
What receptors control water intake?
osmoreceptors in the anterior hypothalamus control water intake by altering thirst and renal water excretion by altering ADH release
63
What magnitude change in Posm can be sensed by the osmoreceptors?
greater than or equal to 1% change
64
Where is ADH released from?
the neurohypophysis in posterior pituitary
65
How is a high volume state sensed?
arterial and carotid baroreceptors respond to vascular stretch also sensed in the JGA
66
What magnitude change in vascular stretch can the baroreceptors sense?
8-10% change in volume increase in stretch signals SON and PVN and body adjusts
67
In what situation is the RAAS system activated?
in cases of low BP or low perfusion at kidneys in order to increase BP
68
What cells release renin
granular cells of the JGA
69
ACtion of renin
promotes conversion of angiotensinogen (liver) to angiotensin I
70
What does ACE do? Where is it released from?
released from lungs converts angiotensin I to angiotenin II
71
What is the action of ATII?
increase Na+ reabsorption in proximal tubule induces thirst stimulates aldosterone production in adrenal cortex promotes ADH release
72
What is the stimulus for the RAAS system?
decrease in circulating volume which increases renal sympathetic activity (B adrenergic receptors) which increase afferent arteriole constriction which reduces Na+ deliver to macular densa which causes renin release
73
Action of ADH
acts in collecting duct to increase H2O reabsorption ADH acts on the V2 receptor (G protein coupled receptor with adenylyl cyclase)--\> converts ATP to cAMP--\>produces PKA--\>PKA promotes migration of AQP2 to plasma membrane adjecent to lumen--\>[most water flows through and with NaCl in proximal tubule//10% flows back in descending limb]--\>ADH acts on COLLECTING DUCT to increase AQP2 expression on lumen membrane
74
What would an ADH deficiency result in?
inability to concentrate urine (i.e in diabetes insipidus)
75
Calculate filtered load
Px X GFR = "filtered load" where GFR = UxV/Px
76
Calculate BP
BP=CO X SVR
77
Fractional Excretion of water
FEwater = V/GFR
78
Fractional Excretion of x
FEx = UxV/(GFR X Px)
79
percent Fractional Excretion
%FE = FE X 100
80
Describe renal anatomy
