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Veterinary Physiology > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

___% of bwt is ICF

A

40%

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2
Q

___% of bwt is ECF

A

20%

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3
Q

___% of bwt is plasma (____% of ECF)

A

4-5%; 20%

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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)

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5
Q

animals require ___ mL of water per 1 kCal energy

A

1 mL

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6
Q

T/F large animals require relatively more water than small animals

A

F; caloric intake is a log function of BW

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7
Q

what are the three pathways for water movement

A

lipid pathway (simple diffusion); water channels (aquaporins); pores/intercellular gaps (glomerulus)

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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

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9
Q

osmotic gradient

A

the difference in particle concentrations on 2 sides of a membrane

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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)

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11
Q

osmolarity is measured in solute/____ whereas osmolality is measured in solute/___

A

osmolarity: solute/L of water; osmolality: solute/kg of water

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12
Q

tonicity

A

the concentration of solutes that cannot readily cross membranes, and thus influence water movement

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13
Q

T/F fluid moves across a membrane until the tonicities are the same

A

T

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14
Q

what determines osmolarity in the ECF? What is the MAIN one

A

glucose, anions (Cl, HCO3), sodium; Na

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15
Q

what determines osmolarity in the ICF? what is the MAIN one

A

potassium and anions (Cl, HCO3); K

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16
Q

what is the major determinant of extracellular fluid volume

A

sodium

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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

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18
Q

what balances ion concentrations via several complex mechanisms

A

the renal system

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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

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20
Q

what three forces balance fluid distribution between ICF/ECF

A

osmotic, oncotic and physical forces

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21
Q

When there is only FLUID LOSS, what happens to ICF and ECF compartments

A

losses are equally shared

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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

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23
Q

What disturbances cause edema and effusions

A

Changes in plasma protein level or capillary pressure

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24
Q

Dehydration

A

lack of sufficient body fluid

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25
Q

What tests are used to initially assess dehydration

A

Skin tent and mucous membranes

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26
Q

What non-specific signs can indicate dehydration

A

tachycardia, sunken eyes, delayed CRT, hypotension

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27
Q

What laboratory signs indicate dehydration

A

PCV and TP increased

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28
Q

T/F change in BW over the course of time in hospital will reflect changes in hydration

A

T

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29
Q

provided kidneys are functional, urine production should ________ fluid intake

A

=

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30
Q

How is dehydration expressed clinically

A

% loss in BW

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31
Q

What is a balanced vs unbalanced solution

A

Balanced has same ion concentrations as ECF (no movement); unbalanced has different ion concentrations from ECF

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32
Q

What are crystalloids

A

Solutions containing ions and solutes that can move freely between different compartments (ex. between ICF and ECF)

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33
Q

What are colloids

A

Solutions containing larger molecules that cannot leave plasma and therefore exert an osmotic effect to maintain the volume of fluid in the vascular space

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34
Q

If an animal is in shock, you want to give them _______

A

colloids (ex. dextrans and hetastarch)

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35
Q

isotonic solutions effect

A

increase ECF; no change in ICF

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36
Q

hypotonic solutions effect

A

decreases ECF osmolarity; net increase in both ECF and ICF

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37
Q

hypertonic solutions effect

A

huge increase in ECF osmolarity; increase in ECF and decrease in ICF

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38
Q

0.9% NaCl, plasmalyte A/148 and LRS

A

isotonic solutions (will increase ECF)

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39
Q

0.45% NaCl

A

hypotonic solution (will increase ECF and ICF)

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40
Q

7.5% NaCl

A

hypertonic solution (will increase ECF and decrease ICF)

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41
Q

BUN is a product of ____________ metabolism

A

amino acid

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42
Q

Cr and SDMA are products of __________ metabolism

A

muscle and cellular

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43
Q

T/F ketones and sulphates are reabsorbed in the kidney

A

F; they get excreted

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44
Q

What are the endocrine functions of the kidney

A

RAAS; EPO production (regulates RBC production); vitamin D metabolism (converts 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3)

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45
Q

what are the 3 functions of the kidney

A

excretion of waste (nitrogenous, toxins, drugs), endocrine, regulate ECF volume and bp

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46
Q

what are the vascular components of the kidney

A

glomerulus, afferent arteriole, efferent arteriole, glomerular capillaries, peritubular capillary, vasa recta

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47
Q

what are the tubular components of the kidney

A

bowman capsule, proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting tubule/duct

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48
Q

what does the juxtaglomerular apparatus consist of

A

afferent/efferent arterioles, macula densa, juxtaglomerular cells, mesangial cells

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49
Q

the juxtaglomerular apparatus is responsible for

A

renin release

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50
Q

what is the macula densa

A

specialized portion of distal tubular epithelial cells that are adjacent to the JG cells

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51
Q

juxtaglomerular cells lie between

A

the afferent arteriole and the distal convoluted tubule

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52
Q

the JG apparatus is important for (2)

A

local regulation of GFR and systemic bp regulation

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53
Q

T/F the glomerulus, under normal conditions, allows complete retention of plasma proteins

A

T

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54
Q

why is GFR important

A

it is maintained in the normal kidney, determining GFR is a key step is assessing renal function clinically

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55
Q

GFR is _______ correlated with body size

A

inversely

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56
Q

what is the size cutoff for GFR

A

small molecules <2nm pass; molecules >4nm retained

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57
Q

what contributes to the filter membrane of the glomerulus

A

fenestrated endothelium, glomerular BM, podocytes

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58
Q

what about molecules that are 2-4nm

A

variable filtration, depending on electrical charge and deformability

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59
Q

T/F -ve charged proteins tend to flow more easily

A

F; + flow more easily, - tend to be retained

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60
Q

what molecules must be absorbed from glomerular filtrate

A

Na, K, Cl, HCO3, glucose

61
Q

glomerulonephritis is associated with

A

protein-losing nephropathy; immune-mediated

62
Q

what facors influence GFR

A
  • renal blood flow (RBF)
  • renal perfusion pressure (PGC)
  • surface area
  • ultrafiltration coefficient (KUF)
  • balance of P and π in capillaries and tubule lumen
63
Q

Increased resistance in the afferent arteriole has what effect on GFR, RBF and PGC

A

dec GFR, dec RBF, dec PGC

64
Q

Increased resistance in the efferent arteriole has what effect on GFR, RBF and PGC

A

inc GFR, dec RBF, inc PGC

65
Q

Decreased resistance in the afferent arteriole has what effect on GFR, RBF and PGC

A

inc GFR; inc RBF, inc PGC

66
Q

Decreased resistance in the efferent arteriole has what effect on GFR and RBF, and PGC

A

dec GFR; inc RBF, dec PGC

67
Q

autoregulation maintains a nearly constant GFR at _________ when MAP is between ___________

A

180L/d; 80-180 mmHg

68
Q

if you increase pressure in the afferent arteriole, it will

A

constrict

69
Q

if you decrease pressure in the afferent arteriole, it will

A

dilate

70
Q

what mediates the myogenic response

A

stretch receptors (open and close ion channels)

71
Q

what modulates the myogenic response

A

local factors (ex. prostaglandins, NO)

72
Q

how do hormones and autonomic neurons contribute to renal autoregulation

A

change resistance in arterioles; change the filtration coefficient by altering the tension on podocytes

73
Q

T/F sympathetic stimulation increases renin release (as well as increases vascular resistance)

A

T

74
Q

describe RAAS

A
  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
Q

renin comes from the __________ and angiotensinogen comes from the ________

A

kidney; liver

76
Q

what stimulates the release of renin (what state of the body)

A

by an decrease in bp

77
Q

angiotensin II, in addition to causing vasoconstriction in the kidney, causes what endocrine effects (2)

A
  1. stimulates release of aldosterone from the adrenal cortex (regulates fluid volume)
  2. stimulates release of ADH from the posterior pituitary (regulates osmolarity)
78
Q

macula densa senses increased bf as

A

increased NaCl

79
Q

describe tubuloglomerular feedback

A

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
Q

what is a consequence of high sodium in the diet

A

decreases GFR via tubuloglomerular feedback, which worsens kidney function

81
Q

T/F Tubuloglomerular feedback inhibits renin secretion

A

T

82
Q

hydrostatic pressure in the glomerular capillary is maintained at ______ due to autoregulatory pathways for GFR

A

50-60 mmHg

83
Q

what is the effect of reduced renal perfusion pressure on autoregulation

A
  1. decrease in myogenic reflex and TGF - > decreases resistance in afferent A
  2. increase in angiotensin II -> increased resistance in efferent A
84
Q

what is the effect of increased renal perfusion pressure on autoregulation

A
  1. increased myogenic reflex and TGF -> increased resistance in afferent A
  2. decreased angiotensin II -> decreased resistance in efferent A
85
Q

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

A

filtered and not reabsorbed/secreted

86
Q

what are two classic substances used to measure filtration and a more recent marker

A

inulin and creatinine; SDMA

87
Q

how is glomerular function assessed in general practice

A

by seeing if creatinine falls in the normal serum range; if filtration is impaired, creatinine will rise in the blood

88
Q

an increase in creatinine, urea, SDMA and other nitrogenous waste in blood is called

A

azotemia

89
Q

azotemia can be (3), give an example of each

A

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
Q

what is uremia

A

the clinical signs associated with renal failure and increased BUN/creatinine

91
Q

to examine if the glomeruli is leaky, look for ________ in the _________; to examine if the glomeruli are filtering enough (GFR), look for __________ in the _________

A

protein; urine; BUN/creatinine/SDMA; blood

92
Q

leaky glomeruli cause ________ whereas not enough filtration causes ________

A

proteinuria; azotemia

93
Q

the effectiveness of reabsorption is reflected in the _________ and ___________ of urine

A

volume; specific gravity (ion concentration)

94
Q

T/F secretion occurs in the loop of Henle

A

F

95
Q

What is reabsorbed in the proximal tubule (PCT)

A
  • NaCl (60%)
  • water (60%)
  • bicarb (60-85%)
  • glucose (100%)
  • AA (100%)
96
Q

What is secreted in the proximal tubule

A

creatinine (why it isn’t a perfect maker of glomerular filtration)

97
Q

90-95% of water absorption is

A

transcellular

98
Q

what type of transport requires favorable electrochemical gradients

A

paracellular

99
Q

what is reabsorbed via solvent drag

A

Mg, P, Ca

100
Q

diuretics tend to target

A

reabsorption of Na (block this so that water is also not reabsorbed)

101
Q

what is the principle driver of reabsorption

A

Na/K ATPase

102
Q

how is Cl reabsorbed

A

paracellular: diffusion with Na
transcellular: Cl/anion exchange; Cl channels at basolateral membrane

103
Q

how is HCO3 ultimately reabsorbed

A

via Na/HCO3 cotransport

104
Q

how is glucose reabsorbed

A
  1. Na/glucose/AA symport
    2/ GLUT1/GLUT2 on basolateral membrane
105
Q

what is the glucose threshold

A

10 mmol/L

106
Q

where are many organic ions, drugs and toxins excreted

A

PCT

107
Q

describe the limbs of the loop of henle

A

thin descending, thin ascending, thick ascending

108
Q

the descending limb is permeable to ________ and less permeable to _________

A

water; NaCl

109
Q

what occurs in the thin ascending limb

A

a small amount of NaCl is reabsorbed by diffusion

110
Q

the thick ascending limb is permeable to ___________ and impermeable to __________

A

K, Cl, Na (via active reabsorption); water

111
Q

what is the cotransporter for Na, Cl, and K called and where is it

A

NKCC2; in thick ascending limb of the loop of henle

112
Q

what is the osmolarity of the fluid by the end of the loop of henle? what about the interstitium at the same spot?

A

100 mM (very dilute); 300 mM

113
Q

what happens to salt removed from the fluid

A

carried to the medulla by the vasa recta (>1000 mM near the deepest part of the medulla)

114
Q

what is reabsorbed in the distal tubule and how

A

NaCl; via Na/Cl cotransport and followed by Na/K ATPase and a Cl channel

115
Q

the distal tubule is (permeable/impermeable) to water

A

impermeable (further decreases osmolarity in the tubular fluid)

116
Q

what is reabsorbed in the collecting duct and how

A

last bit of Na and Cl; Na passively through an Na channel (exits via Na/K ATPase); Cl through paracellular diffusion

117
Q

what 3 processes are required to dilute urine

A
  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
Q

how does aldosterone help dilute urine

A

reabsorption of Na in the DCT

119
Q

1.008-1.012 is

A

isosthenuria

120
Q

> 1.030 in dogs and >1.040 in cats is

A

hypersthenuria

121
Q

<1.008 is

A

hyposthenuria

122
Q

if the animal is dehydrated and the urine is 1.008-1.012, then this suggests (2)

A
  1. the kidneys aren’t working properly
  2. ADH-hyposecretion
123
Q

what happens to K after a meal

A

loaded into ICF in cells, which acts as a pool for slow release and eventual excretion by the kidneys

124
Q

what moves K into cells

A

insulin, E and aldosterone

125
Q

K reabsorption occurs

A

70% in PT
20% in ascending LH

126
Q

K secretion occurs

A

DT/CD

127
Q

T/F aldosterone increases K reabsorption

A

F

128
Q

T/F increased tubular flow increases K secrettion

A

T

129
Q

T/F most filtered Mg is excreted

A

T

130
Q

T/F creatinine is only released during skeletal muscle damage

A

F; it is released normally at a relatively fixed rate

131
Q

when muscle is damaged, what is released

A

creatine kinase (CK); biomarker

132
Q

creatinine is a _________ of _________ metabolism, produced at a ___________ rate.

A

byproduct; muscle; constant

133
Q

how is ammonia produced

A

by glutamate dehydrogenase from glutamate or glutamine

134
Q

ammonia is used to synthesize ________ in carnivores/most domestic animals and _________ in birds/reptiles

A

urea; uric acid

135
Q

how is urea synthesized (what cycle)

A

Krebs

136
Q

where is the only site with all 5 enzymes for urea synthesis

A

liver

137
Q

what are the main AA in the urea cycle

A

glutamate, aspartate, arginine

138
Q

of the 5 enzymes used to synthesize urea, where are they located

A

2 in mitochondria, 3 in cytosol

139
Q

the urea cycle enzymes ____ with low protein diets and ____ with high protein diets; they also ____ during starvation due to ____ AA catabolism

A

decrease; increase; increase; increased

140
Q

T/F Na, K and Cl all contribute to urine specific gravity and are therefore measured indirectly during urinalysis

A

T

141
Q

T/F it is normal if urine becomes cloudly on standing or refrigeration

A

T

142
Q

a normal urine pH in carnivores is _______ and herbivores is _________

A

acidic; alkaline

143
Q

T/F hyaline, granular casts at low levels are normal

A

T

144
Q

T/F cellular casts are normal

A

F

145
Q

T/F a small number of cells and bacteria is normal

A

T

146
Q

what is glomerulotubular balance (GTB)

A

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
Q

what is pressure natriuresis

A

pressure changes in the kidney vasculature directly alter Na excretion

148
Q

what triggers aldosterone release

A

ang II, ACTH, and hyperkalemia

Veterinary Physiology (11 decks)

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