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Renal Physio Flashcards

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1
Q

most important role of the kidney

A

regulation of vol and composition of ECF

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2
Q

main functions of the kidney

A

reg vol and composition of ECF
excrete metab waste products
produce hormones and other circulating factors

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3
Q

each kidney contains ___ nephrons

A

1 million

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4
Q

nephron consists of ___

A

renal corpuscle

tubule

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5
Q

renal corpuscle contains?

A

glomerulus

Bowman’s capsule

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6
Q

ultrafiltrate

A

fluid in Bowman’s space free of cells and proteins

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7
Q

renal tubule

A

cont with Bowman’s capsule, narrow cylinder made of up a single layer of epithelial cells resting on a BM

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8
Q

path of ultrafiltrate

A 
tubule
CD
calyces
pelvis of kidneys
ureter
bladder
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9
Q

excretion rate=

A

filtration rate + secretion rate - reabsorption rate

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10
Q

layers of the filtration barrier

A

single celled cap epithelium with fenestrations
BM
single celled epithelial layer of Bowman’s capsule

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11
Q

what makes up the BM of the filtration barrier?

A

negatively charged glycoproteins

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12
Q

role of BM of filtration barrier

A

prevent large, neg charged solutes from crossing

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13
Q

podocytes

A

epithelial cells of the visceral layer of Bowman’s capsule

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14
Q

filtration slit

A

4nm spaces between pedicels of podocytes

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15
Q

what makes up the diaphragm of the filtration slits?

A

nephrin
podocin
lipid rafts

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16
Q

what size of molecules are rejected by the filtration barrier?

A

> 3.6 nm

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17
Q

what size of molecules are filtered by the filtration barrier?

A

<1 nm

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18
Q

kidneys receive what % of CO?

A

20%

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19
Q

average GFR

A

125ml/min

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20
Q

filtration fraction=

A

GFR/RPF

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21
Q

GFR=

A

Kf[(Pgc-Pbs)-(Pigc-Pibs)

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22
Q

filtration coefficient

A 
Kf
function of the permeability of the glomeruli and their SA
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23
Q

what can reduce the SA of the glomerulus?

A

contractions of podocytes and mesangial cells under the influence of AII or epi

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24
Q

oncotic pressure in bowman’s space=

A

0

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25
how does the hydrostatic pressure change along the glomerular cap?
its relatively high at the afferent end and only changes slightly at the efferent end bc of low resistance
26
large filtration of water and retention of proteins leads to ____
progressive increase in oncotic pressure as fluid moves to the efferent end
27
reabsorption
movement of substances from tubular lumen to the peritubular cap
28
secretion
movement of substances from peritubular cap to the tubular lumen
29
where do most reabsorption of solutes and water take place?
proximal tubule
30
where does concentration and dilution of urine take place?
loop of Henle
31
where does fine tuning and hormone action take place?
distal tubule | collecting ducts
32
filtered load
amount of substance filtered per unit time
33
filtered load=
plasma conc x GFR
34
amount excreted per unit time=
urine conc x urine flow rate
35
if excreted
reabsorption
36
if excreted>filtered there is net ___ by the tubules
secretion
37
__% of filtered water is reabsorbed
99
38
2/3 of salt and water filtered at the glomerulus are reabsorbed at the ___
proximal tubule
39
most of the oxygen consumed by the kidneys is used for ___
energizing Na transport
40
what drives water reabsorption in the proximal tubule?
cont reabsorption of Na and Cl creates an increase in osmolality of the intracellular spaces
41
what drives water reabsorption in the descending limb of Henle?
high osmolality of the medullary interstitium
42
what part of the tubule is impermeable to water?
ascending limb | distal tubule
43
what regulates permeability of water at the CD?
ADH
44
how is glucose reabsorbed in the proximal tubule?
Na dependent transporters
45
SGLT2
low affinity/high capacity | 1:1
46
SGLT1
high affinity/low capacity | 2Na:1glc
47
where are SGLT2?
early PT
48
where are SGLT1?
late PT
49
how does glucose exit cells in the early segment of the PT?
GLUT2
50
how does glucose exit cells in the late segment of the PT?
GLUT1
51
what mechanism of transport is glucose transport?
Tm-limited mechanism
52
2 most important substances secreted by the tubules
H+ | K+
53
where does most of the secretion of anions and cations take place?
late PT
54
clearance
rate at which a particular substance is removed by the kidneys from the blood
55
Cx=
urine conc x urine flow rate/plasma conc
56
if the clearance of a freely filtered substance is less than the clearance of inulin the substance is ____
reabsorbed
57
if the clearance of a freely filtered substance is greater than the clearance of inulin the substance is ____
secreted
58
the clearance of PAH measures the ___
renal plasma flow
59
the urine/plasma inulin ratio is an indicator of?
the fraction of filtered water that is reabsorbed throughout the tubular system
60
effect of afferent constriction on RBF
decreases RBF
61
effect of afferent constriction on Pgc
decreases Pgc
62
effect of efferent constriction on RBF
decreases RBF
63
effect of efferent constriction on Pgc
increases Pgc
64
effect of afferent dilation on RBF
increases RBF
65
effect of afferent dilation on Pgc
increases Pgc
66
effect of efferent dilation on RBF
increases RBF
67
effect of efferent dilation on Pgc
decreases Pgc
68
small constriction of the efferent arteriole causes what change in GFR?
small increases GFR
69
large constriction of the efferent arteriole causes what change in GFR?
decreases GFR
70
afferent dilation causes what change in GFR?
increases GFR
71
afferent constriction causes what change in GFR?
decreases GFR
72
myogenic response
afferent arteriole smooth muscle contracts when stretched and relaxes on decreased distending pressure
73
how is the myogenic response mediated?
stretch sensitive cation channels
74
AII causes
a preferential increase in efferent arteriolar resistance and prevents a fall in Pgc and GFR
75
tubuloglomerular feedback
refers to changes in GFR that can be induced by chnages in the flow rate of fluid perfusing macula densa cells at the end of the ascending loop of Henle
76
when is tubuloglomerular feedback important?
when renal pressure increases
77
what is the likely mechanism of tubuloglomerular feedback?
macula densa cells sense increase in NaCl and secrete adenosine or ATP in response
78
what receptor does adenosine bind to in the afferent arteriolar smooth muscle?
A1
79
what does adenosine cause?
vasoconstriction
80
volume contraction ___ the sensitivity of tubuloglomerular feedback
increases
81
volume expansion ___ the sensitivity of tubuloglomerular feedback
decreases
82
most important day to day regulation of renal hemodynamics
autoregulation
83
decrease in blood volume or bp leads to ____
sympathetic nerve activation
84
what receptor does NE interact with in the afferent arterioles?
alpha 1
85
what does NE cause?
afferent constriction | decreased RBF and GFR
86
sympathetic activation of beta 1 receptors on granular cells causes ___
release of renin
87
what stimulates renal prostaglandin production
NE | AII
88
what do prostaglandins do?
dampens vasoconstrictor effects of sympathetic NS and AII to prevent renal ischemia
89
what produces endothelin?
endothelial and mesangial cells
90
action of endothelin
vasoconstrictor of afferent and efferent arterioles
91
what produces NO?
endothelial and macula densa cells
92
action of NO
vasodilator released tonically in renal circulation
93
what stimulates release of NO?
expansion ECF vol ATP bradykinin histamine
94
action of dopamine and ANP
vasodilators | increase RBF and GFR
95
how does ANP raise GFR without changing RBF?
dilates afferent arteriole | constricts efferent arteriole
96
glomerulotubular balance
when sodium balance is normal, Na+ and water reabsorption increase in parallel with an increase in GFR and Na load
97
2 mechanisms of glomerulotubular balance
starling forces | increased filtration of organic solutes
98
where does glomerulotubular balance take place?
PT loop of Henle DT
99
what secretes ADH?
posterior pituitary/neurohypophysis
100
where are AQP1?
PT | descending thin mib
101
where are AQP7?
PT
102
where are AQP2?
CD
103
where are AQP3 and 4?
CD
104
what AQP is inserted in the CD lumen due to ADH?
AQP2
105
regulation of plasma osmolality and Na conc is achieved by ____
alterations in water intake and excretion
106
osmotic stratification
progressive increase of interstitial osmolality from cortex to papilla
107
where does creation of osmotic gradients mainly occur?
ascending limb of the loop of Henle
108
where does urea recycling take place?
terminal inner medullary collecting duct
109
effects of ADH
increased water reabsorption increased IMCD urea reabsorption increased salt reabsorption in the TAL decreased vasa recta blood flow
110
obligatory water loss
0.5L | required for the excretion of waste products
111
aquaporins
water channels | homotetramers of integral membrane proteins
112
binding of ADH to its receptor activates ___
adenylate cyclase via a G-protein leads to formation of cAMP and phosphorylation of proteins leads to incorporation of AQP2 into luminal membranes of the CD
113
AII ___ ANP secretion
stimulates
114
AII ___ ADH secretion
inhibits
115
what is sensed in vol regulation?
ECV
116
what is sensed in osmo regulation?
plama osmolality
117
what are the vol regulation sensors?
baroreceptors
118
what are the osmo regulation sensors?
osmoreceptors
119
what are the vol regulation effectors?
RAAS sympathetic NS ANP ADH
120
what are the osmo regulation effectors?
ADH | thirst
121
how much Na+ is in bone?
40%
122
how much available Na is in the ECF?
90%
123
effective circulating vol
unmeasured volume that reflects the extent of tissue perfusion
124
major baroreceptors involved in sensing Na
central great arterial vessels cardiac atria afferent arterioles in kidneys
125
decreased stretch in the afferent arteriole of the kidney stimulates ___
secretion of renin
126
how are adjustments in Na secretion accomplished?
changes in filtered Na load | determined by GFR and Na reabsorption
127
which parts of the tubule are load-dependent Na reabsorption
PT | TAL
128
increases in Na tend to __ GFR
increase
129
decreases in Na tend to __ GFR
decrease
130
decreased Na/ECF vol causes arteriolar ___
vasoconstriction
131
what is the method of Na entry into cells in the early PT?
cotransport with organic solutes | in exchange for H+
132
what is the method of Na entry into cells in the late PT?
Na-H exchanger coupled with Cl-OH exchanger
133
what is the method of Na entry into cells in the TAL?
Na is cotransported with K and Cl by the NKCC2 transporter
134
what is the method of Na entry into cells in the early DT?
Na is cotransported with Cl by the NCC transporter
135
what is the method of Na entry into cells in the late DT?
epithelial Na channel- ENaC
136
what is the NCC transporter sensitive to?
thiazides
137
what is the ENaC sensitive to?
amiloride
138
what upregulates the ENaC channel?
aldosterone
139
what stimulates secretion of ADH?
small increases in plasma osmolality | large reductions in ECF vol
140
when are prostanoids released?
when ECF vol/Na increases
141
action of prostanoids and NO
inhibit Na reabsorption in the TAL
142
aldosterone
steroid hormone secreted by glomerulosa cells of the adrenal cortex
143
renin
proteloytic enzyme secreted by the juxtaglomerular cells | cleaves angiotensinogen to produce AI
144
functions of AII
stimulation of aldosterone secretion by the adrenal cortex arteriolar vasoconstriction stimulation of Na reabsorption by the PT stimulation of ADH and thirst
145
what cells does AII act on?
principal cells of the distal nephron
146
early effects of activation of the aldosterone receptor
recruitment of the apical Na channel and the basolateral Na/K ATPase
147
later effects of activation of the aldosterone receptor
increase synthesis of the apical Na channel and the basolateral Na/K ATPase
148
3 inputs to the juxtaglomerular cells that increase renin secretion in response to ECF/Na depletion
sympathetic nerve activity perfusion pressure delivery of NaCl to the macula densa
149
atrial natriuretic peptide
28 AA peptide produced and stored by cardiac myocytes
150
actions of ANP
relaxes vascular smooth muscle promotes NaCl and water excretion increases GFR and Na filtered load inhibits aldosterone secretion by the adrenal cortex inhibits Na reabsorption by the CD inhibits ADH secretion by the posterior pituitary
151
urodilatin
32 AA peptide secreted by DT and CD
152
urodilatin action
acts locally to inhibit Na reabsorption
153
local factors that inhibit Na reabsorption
NO prostanoids kinins
154
what is the most abundant cation in the body?
K+
155
where is most of the body K located?
inside cells at a conc of 150 mEq/L
156
where is most intracellular K?
muscle cells | some in RBCs, liver, bone
157
normal range of plasma K
3.5-5 mEq/L
158
roles of K+
cofactor for enzymes regulator of muscle blood flow during exercise sets cell membrane potential
159
what activates the Na/K ATPase after ingestion of K+?
initial rise of plasma K epi insulin
160
in acidotic states, a drop of 0.1 pH results in an increase of ___ plasma K+
0.6 mEq/L
161
where is most of the filtered K reabsorbed?
PT | TAL
162
how is K reabsorbed in the PT?
diffusion through the intercellular pathway
163
how is K reabsorbed in the TAL luminal membrane?
NKCC2 transporter
164
what inhibits NKCC2?
loop diuretics
165
how is K transported at the TAL basolateral membrane?
K-Cl cotransport | K channels
166
___ can secrete or reabsorb K+
distal segments
167
principal cell role in K+ transport
secretion
168
intercalated alpha cell role in K+ transport
mediates reabsorption
169
where does K secretion mostly take place?
late distal and cortical collecting tubules
170
what channels does K secretion involve?
ROMK BK KCl cotransport
171
at the cellular level the 3 factors controlling the rate of K secretion are
activity of Na/K ATPase electrochemical gradient for K movement across the apical membrane permeability of the apical membrane to K
172
how does hyperkalemia stimulate K secretion
stimulates Na/K ATPase increases permeability of luminal membrane to K induces aldosterone secretion
173
how does a high flow rate promote K secretion?
deforms mechano sensitive central cilium of the principal cells causes release of Ca opens Ca sensitive K channels
174
role of diuretics
increase rate of tubular flow through the distal nephron
175
spironolactone
competitive inhibitor of aldosterone
176
triamterene and amiloride
diuretic that inhibits lumenal Na channel in the distal nephron
177
reabsorption of bicarb and secretion of bicarb require ____
secretion of H+ from body to urine
178
2 mechanisms of H+ secretion
ion exchange | primary active H+ transport
179
how is H+ transported in the PT?
Na-H and Na-NH4 exchange via the NHE3 transporter
180
where does primary active H+ transport mainly occur?
collecting duct of distal nephron
181
where is most of the filtered bicarb reabsorbed?
PT
182
predominant urine buffers
phosphate | ammonia
183
titratable acidity
total contribution of all buffers of pK's in the neighborhood of physio urine pH
184
titratable acidity accounts for __ of acid excretion in the urine
1/3
185
how does the CD secrete NH3, NH4, H+
Rh-glycoproteins
186
ammonium trapping
once NH3 is in the renal tubule cell it reacts with H+ to form NH4 which can't permeate the cell
187
acute response to acidosis
insertion of transporters
188
chronic response to acidosis
transcription/translation of genes/mRNA for transporters and enzymes required for ammoniagenesis
189
urinary net acid excretion NAE=
(Uta+UNH4-UHCO3)V
190
what secretes endothelin-1
endothelial cells and PT cells
191
what stimulates secretion of endothelin-1?
acidosis
192
actions of endothelin-1
increase expression of NHE-3 and NBCe1
193
what stimulates secretion of PTH?
acidosis
194
actions of PTH
inhibits phosphate reabsorbtion by the PT so more of it is available as a buffer
195
role of principal/granular cell in the distal nephron
carries out Na reabsorption
196
role of intercalated cells
regulate acid-base status
197
role of alpha intercalated cells
secrete H+ into the lumen
198
role of beta intercalated cells
secrete HCO3-
199
alpha intercalated cells are upregulated during ___
acidosis
200
beta intercalated cells are upregulated during ___
alkalosis
201
change in [H+] in resp acidosis
increase
202
change in [H+] in resp alkalosis
decrease
203
change in [H+] in metab acidosis
increase
204
change in [H+] in metab alkalosis
decrease
205
change in [HCO3-] in resp acidosis
increase
206
change in [HCO3-] in resp alkalosis
decrease
207
change in [HCO3-] in metab acidosis
decrease
208
change in [HCO3-] in metab alkalosis
increase
209
change in pCO2 in resp acidosis
increase
210
change in pCO2 in resp alkalosis
decrease
211
change in pCO2 in metab acidosis
decrease
212
change in pCO2 in metab alkalosis
increase
213
cause of HCO3- change in resp acidosis
increase pCO2 and renal compensation
214
cause of HCO3- change in resp alkalosis
decrease pCO2 and renal compensation
215
cause of HCO3- change in metab acidosis
HCO3- loss, H+ gain
216
cause of HCO3- change in metab alkalosis
HCO3- gain, H+ loss
217
cause of CO2 change in resp acidosis
impaired lung function
218
cause of CO2 change in resp alkalosis
increased ventilation
219
cause of CO2 change in metab acidosis
reflex resp compensation
220
cause of CO2 change in metab acidosis
reflex resp compensation
221
free water clearance
amount of solute-free water that the kidney can excrete per unit time
222
CH2O=
V-Cosm
223
when urine osmolarity= plasma osmolarity CH2O=
0
224
what does negative free water represents ___
water reabsorbed by tubules rather than excreted
225
osmolar clearance always ___ with the administration of diuretics
increases
226
administration of a PT diuretic ___ free water clearance
increases
227
administration of a DT loop diuretic ___ free water clearance
decreases
228
renovascular hypertension
inappropriate release of renin due to renal stenosis | leads to hypertension
229
Conn's syndrome
excessive aldosterone production | leads to hypertension
230
Liddle's syndrome
excessive Na reabsorption | leads to hypertension
231
main causes of kidney failure
diabetes | high bp
232
where do osmotic diuretics act?
PT
233
osmotic diuretic action
mannitol is filtered and remains in the tubule to decrease the difference btwn interstitium and tubule
234
where do CA inhibitors act?
PT
235
where do loop diuretics act?
TAL
236
loop diuretic action
blocks NKCC2 channel
237
where do thiazides act?
early DT
238
thiazide action
blocks Na-Cl channel in early DT
239
where do K sparing diuretics act?
late DT

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