Renal Physiology Flashcards
(148 cards)
1
Q
___% of bwt is ICF
A
40%
2
Q
___% of bwt is ECF
A
20%
3
Q
___% of bwt is plasma (____% of ECF)
A
4-5%; 20%
4
Q
which of the following does not contribute to ECF water balance
- drinking
- saliva
- metabolic water
- sweating and panting
- renal free water loss (regulated by ADH)
- obligatory renal losses
A
metabolic water (contributes to ICF)
5
Q
animals require ___ mL of water per 1 kCal energy
A
1 mL
6
Q
T/F large animals require relatively more water than small animals
A
F; caloric intake is a log function of BW
7
Q
what are the three pathways for water movement
A
lipid pathway (simple diffusion); water channels (aquaporins); pores/intercellular gaps (glomerulus)
8
Q
osmotic pressure
A
the hydrostatic pressure required to oppose the movement of water through a semi-permeable membrane in response to an osmotic gradient
9
Q
osmotic gradient
A
the difference in particle concentrations on 2 sides of a membrane
10
Q
osmolarity
A
the concentration of solutes in solution that exert osmotic force (includes both those that can readily cross a membrane and those that cannot)
11
Q
osmolarity is measured in solute/____ whereas osmolality is measured in solute/___
A
osmolarity: solute/L of water; osmolality: solute/kg of water
12
Q
tonicity
A
the concentration of solutes that cannot readily cross membranes, and thus influence water movement
13
Q
T/F fluid moves across a membrane until the tonicities are the same
A
T
14
Q
what determines osmolarity in the ECF? What is the MAIN one
A
glucose, anions (Cl, HCO3), sodium; Na
15
Q
what determines osmolarity in the ICF? what is the MAIN one
A
potassium and anions (Cl, HCO3); K
16
Q
what is the major determinant of extracellular fluid volume
A
sodium
17
Q
T/F intracellular fluid regulation relies on passive movement of K through leaky channels in response to the Na concentration in the ECF
A
T
18
Q
what balances ion concentrations via several complex mechanisms
A
the renal system
19
Q
the sum of the osmotic effects of ions, plus the oncotic effects of proteins, leads to an effective plasma osmolarity of approximately…
A
300 mOsm/L
20
Q
what three forces balance fluid distribution between ICF/ECF
A
osmotic, oncotic and physical forces
21
Q
When there is only FLUID LOSS, what happens to ICF and ECF compartments
A
losses are equally shared
22
Q
When there is ION LOSS, what happens to ICF and ECF compartments
A
fluid balance becomes disturbed because the body can not longer move fluids osmotically
23
Q
What disturbances cause edema and effusions
A
Changes in plasma protein level or capillary pressure
24
Q
Dehydration
A
lack of sufficient body fluid
25
What tests are used to initially assess dehydration
Skin tent and mucous membranes
26
What non-specific signs can indicate dehydration
tachycardia, sunken eyes, delayed CRT, hypotension
27
What laboratory signs indicate dehydration
PCV and TP increased
28
T/F change in BW over the course of time in hospital will reflect changes in hydration
T
29
provided kidneys are functional, urine production should ________ fluid intake
=
30
How is dehydration expressed clinically
% loss in BW
31
What is a balanced vs unbalanced solution
Balanced has same ion concentrations as ECF (no movement); unbalanced has different ion concentrations from ECF
32
What are crystalloids
Solutions containing ions and solutes that can move freely between different compartments (ex. between ICF and ECF)
33
What are colloids
Solutions containing larger molecules that cannot leave plasma and therefore exert an osmotic effect to maintain the volume of fluid in the vascular space
34
If an animal is in shock, you want to give them _______
colloids (ex. dextrans and hetastarch)
35
isotonic solutions effect
increase ECF; no change in ICF
36
hypotonic solutions effect
decreases ECF osmolarity; net increase in both ECF and ICF
37
hypertonic solutions effect
huge increase in ECF osmolarity; increase in ECF and decrease in ICF
38
0.9% NaCl, plasmalyte A/148 and LRS
isotonic solutions (will increase ECF)
39
0.45% NaCl
hypotonic solution (will increase ECF and ICF)
40
7.5% NaCl
hypertonic solution (will increase ECF and decrease ICF)
41
BUN is a product of ____________ metabolism
amino acid
42
Cr and SDMA are products of __________ metabolism
muscle and cellular
43
T/F ketones and sulphates are reabsorbed in the kidney
F; they get excreted
44
What are the endocrine functions of the kidney
RAAS; EPO production (regulates RBC production); vitamin D metabolism (converts 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3)
45
what are the 3 functions of the kidney
excretion of waste (nitrogenous, toxins, drugs), endocrine, regulate ECF volume and bp
46
what are the vascular components of the kidney
glomerulus, afferent arteriole, efferent arteriole, glomerular capillaries, peritubular capillary, vasa recta
47
what are the tubular components of the kidney
bowman capsule, proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting tubule/duct
48
what does the juxtaglomerular apparatus consist of
afferent/efferent arterioles, macula densa, juxtaglomerular cells, mesangial cells
49
the juxtaglomerular apparatus is responsible for
renin release
50
what is the macula densa
specialized portion of distal tubular epithelial cells that are adjacent to the JG cells
51
juxtaglomerular cells lie between
the afferent arteriole and the distal convoluted tubule
52
the JG apparatus is important for (2)
local regulation of GFR and systemic bp regulation
53
T/F the glomerulus, under normal conditions, allows complete retention of plasma proteins
T
54
why is GFR important
it is maintained in the normal kidney, determining GFR is a key step is assessing renal function clinically
55
GFR is _______ correlated with body size
inversely
56
what is the size cutoff for GFR
small molecules <2nm pass; molecules >4nm retained
57
what contributes to the filter membrane of the glomerulus
fenestrated endothelium, glomerular BM, podocytes
58
what about molecules that are 2-4nm
variable filtration, depending on electrical charge and deformability
59
T/F -ve charged proteins tend to flow more easily
F; + flow more easily, - tend to be retained
60
what molecules must be absorbed from glomerular filtrate
Na, K, Cl, HCO3, glucose
61
glomerulonephritis is associated with
protein-losing nephropathy; immune-mediated
62
what facors influence GFR
- renal blood flow (RBF)
- renal perfusion pressure (PGC)
- surface area
- ultrafiltration coefficient (KUF)
- balance of P and π in capillaries and tubule lumen
63
Increased resistance in the afferent arteriole has what effect on GFR, RBF and PGC
dec GFR, dec RBF, dec PGC
64
Increased resistance in the efferent arteriole has what effect on GFR, RBF and PGC
inc GFR, dec RBF, inc PGC
65
Decreased resistance in the afferent arteriole has what effect on GFR, RBF and PGC
inc GFR; inc RBF, inc PGC
66
Decreased resistance in the efferent arteriole has what effect on GFR and RBF, and PGC
dec GFR; inc RBF, dec PGC
67
autoregulation maintains a nearly constant GFR at _________ when MAP is between ___________
180L/d; 80-180 mmHg
68
if you increase pressure in the afferent arteriole, it will
constrict
69
if you decrease pressure in the afferent arteriole, it will
dilate
70
what mediates the myogenic response
stretch receptors (open and close ion channels)
71
what modulates the myogenic response
local factors (ex. prostaglandins, NO)
72
how do hormones and autonomic neurons contribute to renal autoregulation
change resistance in arterioles; change the filtration coefficient by altering the tension on podocytes
73
T/F sympathetic stimulation increases renin release (as well as increases vascular resistance)
T
74
describe RAAS
1. JG cells secrete renin when bp drops (stim by sympathetic NS)
2. renin converts angiotensinogen to angiotensin I
3. in the lungs, angiotensin I converted to angiotensin II by ACE
4. angiotensin II directly impacts vasoconstriction
75
renin comes from the __________ and angiotensinogen comes from the ________
kidney; liver
76
what stimulates the release of renin (what state of the body)
by an decrease in bp
77
angiotensin II, in addition to causing vasoconstriction in the kidney, causes what endocrine effects (2)
1. stimulates release of aldosterone from the adrenal cortex (regulates fluid volume)
2. stimulates release of ADH from the posterior pituitary (regulates osmolarity)
78
macula densa senses increased bf as
increased NaCl
79
describe tubuloglomerular feedback
increased GFR -> increased tubular flow rate -> increased NaCl detected by macula densa -> macula densa releases adenosine -> adenosine detected by afferent arteriole -> afferent constricts -> increased resistance in afferent arteriole -> GFR decreases
80
what is a consequence of high sodium in the diet
decreases GFR via tubuloglomerular feedback, which worsens kidney function
81
T/F Tubuloglomerular feedback inhibits renin secretion
T
82
hydrostatic pressure in the glomerular capillary is maintained at ______ due to autoregulatory pathways for GFR
50-60 mmHg
83
what is the effect of reduced renal perfusion pressure on autoregulation
1. decrease in myogenic reflex and TGF - > decreases resistance in afferent A
2. increase in angiotensin II -> increased resistance in efferent A
84
what is the effect of increased renal perfusion pressure on autoregulation
1. increased myogenic reflex and TGF -> increased resistance in afferent A
2. decreased angiotensin II -> decreased resistance in efferent A
85
You can determine GFR by measuring the 1) concentration of a substance in blood 2) concentration in the urine, and 3) the volume of the urine, as long as the substance is
filtered and not reabsorbed/secreted
86
what are two classic substances used to measure filtration and a more recent marker
inulin and creatinine; SDMA
87
how is glomerular function assessed in general practice
by seeing if creatinine falls in the normal serum range; if filtration is impaired, creatinine will rise in the blood
88
an increase in creatinine, urea, SDMA and other nitrogenous waste in blood is called
azotemia
89
azotemia can be (3), give an example of each
prerenal (not enough bloodflow ex. dehydration)
renal (dec # of functioning glomeruli or impaired glomerular function, ex. lepto)
postrenal (distal to the kidney, ex. urolith or bladder rupture)
90
what is uremia
the clinical signs associated with renal failure and increased BUN/creatinine
91
to examine if the glomeruli is leaky, look for ________ in the _________; to examine if the glomeruli are filtering enough (GFR), look for __________ in the _________
protein; urine; BUN/creatinine/SDMA; blood
92
leaky glomeruli cause ________ whereas not enough filtration causes ________
proteinuria; azotemia
93
the effectiveness of reabsorption is reflected in the _________ and ___________ of urine
volume; specific gravity (ion concentration)
94
T/F secretion occurs in the loop of Henle
F
95
What is reabsorbed in the proximal tubule (PCT)
- NaCl (60%)
- water (60%)
- bicarb (60-85%)
- glucose (100%)
- AA (100%)
96
What is secreted in the proximal tubule
creatinine (why it isn't a perfect maker of glomerular filtration)
97
90-95% of water absorption is
transcellular
98
what type of transport requires favorable electrochemical gradients
paracellular
99
what is reabsorbed via solvent drag
Mg, P, Ca
100
diuretics tend to target
reabsorption of Na (block this so that water is also not reabsorbed)
101
what is the principle driver of reabsorption
Na/K ATPase
102
how is Cl reabsorbed
paracellular: diffusion with Na
transcellular: Cl/anion exchange; Cl channels at basolateral membrane
103
how is HCO3 ultimately reabsorbed
via Na/HCO3 cotransport
104
how is glucose reabsorbed
1. Na/glucose/AA symport
2/ GLUT1/GLUT2 on basolateral membrane
105
what is the glucose threshold
10 mmol/L
106
where are many organic ions, drugs and toxins excreted
PCT
107
describe the limbs of the loop of henle
thin descending, thin ascending, thick ascending
108
the descending limb is permeable to ________ and less permeable to _________
water; NaCl
109
what occurs in the thin ascending limb
a small amount of NaCl is reabsorbed by diffusion
110
the thick ascending limb is permeable to ___________ and impermeable to __________
K, Cl, Na (via active reabsorption); water
111
what is the cotransporter for Na, Cl, and K called and where is it
NKCC2; in thick ascending limb of the loop of henle
112
what is the osmolarity of the fluid by the end of the loop of henle? what about the interstitium at the same spot?
100 mM (very dilute); 300 mM
113
what happens to salt removed from the fluid
carried to the medulla by the vasa recta (>1000 mM near the deepest part of the medulla)
114
what is reabsorbed in the distal tubule and how
NaCl; via Na/Cl cotransport and followed by Na/K ATPase and a Cl channel
115
the distal tubule is (permeable/impermeable) to water
impermeable (further decreases osmolarity in the tubular fluid)
116
what is reabsorbed in the collecting duct and how
last bit of Na and Cl; Na passively through an Na channel (exits via Na/K ATPase); Cl through paracellular diffusion
117
what 3 processes are required to dilute urine
1. hypertonic medullary interstitium via countercurrent multiplier
2. dilution of tubular fluid in the thick ascending loop (via reabsorption of NaCl but not H2O)
3. selective water permeability of the CD mediated by ADH
118
how does aldosterone help dilute urine
reabsorption of Na in the DCT
119
1.008-1.012 is
isosthenuria
120
>1.030 in dogs and >1.040 in cats is
hypersthenuria
121
<1.008 is
hyposthenuria
122
if the animal is dehydrated and the urine is 1.008-1.012, then this suggests (2)
1. the kidneys aren't working properly
2. ADH-hyposecretion
123
what happens to K after a meal
loaded into ICF in cells, which acts as a pool for slow release and eventual excretion by the kidneys
124
what moves K into cells
insulin, E and aldosterone
125
K reabsorption occurs
70% in PT
20% in ascending LH
126
K secretion occurs
DT/CD
127
T/F aldosterone increases K reabsorption
F
128
T/F increased tubular flow increases K secrettion
T
129
T/F most filtered Mg is excreted
T
130
T/F creatinine is only released during skeletal muscle damage
F; it is released normally at a relatively fixed rate
131
when muscle is damaged, what is released
creatine kinase (CK); biomarker
132
creatinine is a _________ of _________ metabolism, produced at a ___________ rate.
byproduct; muscle; constant
133
how is ammonia produced
by glutamate dehydrogenase from glutamate or glutamine
134
ammonia is used to synthesize ________ in carnivores/most domestic animals and _________ in birds/reptiles
urea; uric acid
135
how is urea synthesized (what cycle)
Krebs
136
where is the only site with all 5 enzymes for urea synthesis
liver
137
what are the main AA in the urea cycle
glutamate, aspartate, arginine
138
of the 5 enzymes used to synthesize urea, where are they located
2 in mitochondria, 3 in cytosol
139
the urea cycle enzymes ____ with low protein diets and ____ with high protein diets; they also ____ during starvation due to ____ AA catabolism
decrease; increase; increase; increased
140
T/F Na, K and Cl all contribute to urine specific gravity and are therefore measured indirectly during urinalysis
T
141
T/F it is normal if urine becomes cloudly on standing or refrigeration
T
142
a normal urine pH in carnivores is _______ and herbivores is _________
acidic; alkaline
143
T/F hyaline, granular casts at low levels are normal
T
144
T/F cellular casts are normal
F
145
T/F a small number of cells and bacteria is normal
T
146
what is glomerulotubular balance (GTB)
ability of each segment of the proximal tubule to reabsorb a constant fraction of the glomerular filtrate; if high Na, blood flow increases, proximal tubule reabsorbs relatively less Na, more Na/water passes in urine, normalization of blood volume
147
what is pressure natriuresis
pressure changes in the kidney vasculature directly alter Na excretion
148
what triggers aldosterone release
ang II, ACTH, and hyperkalemia
