Exam 4 Condensed Flashcards
What is the filtration fraction?
GFR/RPF
How do you calculate ECF?
20% x weight
How do you calculate ICF?
40% x weight
How do you calculate interstitial fluid?
75% x ECF
How do you calculate plasma volume?
25% x ECF
Intake of an isotonic NaCl solution…
type:
ECF volume:
ECF osmolarity:
type: isosmotic volume expansion
ECF volume: increase
ECF osmolarity: no change
Mild diarrhea…
type:
ECF volume:
ECF osmolarity:
type: isosmotic volume contraction
ECF volume: decrease
ECF osmolarity: no change
High NaCl intake…
type:
ECF volume:
ECF osmolarity:
type: hyperosmotic volume expansion
ECF volume: increase
ECF osmolarity: increase
Excessive sweating…
type:
ECF volume:
ECF osmolarity:
type: hyperosmotic volume contraction
ECF volume: decrease
ECF osmolarity: increase
Excessive water intake…
type:
ECF volume:
ECF osmolarity:
type: hyposmotic volume expansion
ECF volume: increase
ECF osmolarity: decrease
Adrenal insufficiency…
type:
ECF volume:
ECF osmolarity:
type: hyposomotic volume contraction
ECF volume: decrease
ECF osmolarity: decrease
How do you calculate filtered load of a solute?
UF x Us
During reabsorption, filtered load ____ excretion rate of solute
filtered load > excretion rate
During secretion, filtered load ____ excretion rate of solute
filtered load < excretion rate
Why is inulin a good marker for GFR?
it cannot be reabsorbed or secreted
* only filtered and excreted
How do you calculate clearance (GFR) of a solute?
UF x Us / Ps
For inulin, filtered load ____ excretion rate of solute
filtered load = excretion rate
[Creatinine] in plasma is ____________ proportional to GFR
inversely
Does hydrostatic pressure or osmotic pressure favor filtration?
hydrostatic pressure
Does hydrostatic pressure or osmotic pressure favor reabsorption?
osmotic pressure
Is hydrostatic pressure or osmotic pressure the driving force for GFR?
hydrostatic pressure
What happens to renal plasma flow if afferent arterioles are restricted?
decrease
What happens to hydrostatic pressure if afferent arterioles are restricted?
decrease
What happens to GFR if afferent arterioles are restricted?
decrease
What happens to renal plasma flow if efferent arterioles are restricted?
decrease
What happens to hydrostatic pressure if efferent arterioles are restricted?
increase
What happens to GFR if efferent arterioles are restricted?
increase then decrease
When you restrict efferent arterioles, why does hydrostatic pressure increase?
restriction downstream causes build up of pressure upstream cause increased filtration
When you restrict efferent arterioles, why does GFR increase then decrease?
INCREASE: restriction downstream causes build up of pressure upstream cause increased filtration
DECREASE: proteins build up causing osmotic pressure to overcome hydrostatic pressure
What 2 mechanisms auto-regulate renal function?
- myogenic mechanism
- tubuloglomerular feedback
How does auto-regulation of renal function via the myogenic mechanism work?
- increased stretch smooth muscle stretch is sensed in afferent arterioles
- increased intracellular Ca2+
- increased tension
- increase resistance (to counteract stretch)
How does auto-regulation of renal function via the tubuloglomerular feedback work?
- single nephron senses increase in lumenal NaCl (at macula densa)
- increased constriction of arterioles
- decreased GFR/RBF
What 2 things does Angiotensin II increase when secreted?
- increased contraction (increased R and BF)
- increased aldosterone (increase Na+ reabsorption & increased ECF)
What is aldosterone’s affect on Na+?
increased Na+ reabsorption
(to increase ECF volume)
What environment is aldosterone secreted in?
low blood pressure
What are 3 stimulators of aldosterone secretion?
- AT II
- volume contraction
- hyperkalemia
What medication blocks aldosterone and competes for binding of its receptor?
spironolactone
What is the purpose of diuretics?
prevent salt reabsorption to draw fluid into tubules = increased urine production
- prevents fluid build up in body & lowers BP
How do prostaglandins (PGE2) affect kidney function?
local vasodilator allowing for increased blood flow
What affects paracellular movement?
voltage
What affect transcellular movement?
saturation of transporters
Molecules that need to be actively transported can have their transporters saturated, how does that affect…
excretion
reabsorption
filtration
excretion: none
reabsorption: Tm limited
filtration: none
What happens when an active transporter reaches Tm?
transporter becomes saturated
Why is there no glucose excreted at the beginning of the glucose Tm graph?
its all being filtered and reabsorbed
What does the threshold on the glucose Tm graph represent?
plasma concentration at which solute first appears in urine
What segment of the nephron reabsorbs the most water?
proximal tubule
Fluid reabsorption in the proximal tubule is ____osmotic
isosmotic
_____% of Na+ is reabsorbed in the proximal tubule
67%
What is the Vte charge in the early proximal tubule and why?
-4 mV
Na+ is leaving paracellularly making lumen more negative
What drives the reabsorption of Na+ in the early proximal tubule?
negative Vte
What is the Vte charge in the late proximal tubule and why?
+4 mV
Cl- is paracellularly leaving lumen making it more positive
What is GT balance?
67% of Na+ is always reabsorbed in the proximal tubule, regardless of the change in filtered load
What are the 2 factors that affect GT balance?
- peritubular factors (change in starling forces)
- luminal factors (tubule flow)
If you increase the filtration fraction does the osmotic pressure of the peritubular capillary increase or decrease?
How does this aid in GT balance?
increase osmotic pressure
*increased Na+ reabsorption
If you increase the filtration fraction does the hydrostatic pressure of the peritubular capillary increase or decrease?
How does this aid in GT balance?
decrease hydrostatic pressure
more filtration means more solutes need to be absorbed whcich favors osmotic pressure
If you increase filtration fraction, the tubule flow ___________, so what is the affect on solute reabsorption?
increase tubule flow
increased solute reabsorption (spends more time in tubule)
How much glucose, amino acids, and carboxylates are reabsorbed in proximal tubule?
almost 100%
How much potassium and calcium is reabsorbed in proximal tubule?
2/3
What ion closely follows fluid reabsorption?
K+
Where is most of the Ca2+ reabsorbed?
thick ascending limb
How much Mg2+ is reabsorbed in proximal tubule?
15%
What ion is excreted the most and why?
phosphate (aids in excretion of non-volatile acids)
How much phosphate is reabsorbed in proximal tubule?
80%
Reabsorption of phosphate is ____-limited causing it to be excreted in urine
Tm
How much HCO3- is reabsorbed in proximal tubule?
80%
What is an example of an organic/synthetic anion?
PAH
PAH __________ is Tm limited because active transporter is located on _________ side
secretion
basolateral side
The fluid at the end of the loop of henle is ______osmotic
hypotonic
The thin descending limb reabsorbs ______ while the thin/thick ascending limb reabsorbs ________
H2O
NaCl
Fluid movement down the thin descending limb becomes more __________
concentrated
Fluid movement up the thick/thin descending limb becomes more __________
diluted
What transporter reabsorbs NaCl in thick ascending limb?
Na+/K+/Cl- co-transporter
What is the Vte of the thick ascending limb and why?
+10 mV
lots of K+ channels pump K+ into lumen
What is Bartter Syndrome?
defective Na/K/Cl co-transporter
less K+ movement = less ion reabsorption
What is a loop diuretic?
inhibits Na/K/Cl co-transporter
targets thick ascending limb
What 2 ions are mainly transported paracellularly in the thick ascending limb?
Mg2+
Ca2+
Where is most of the Mg2+ reabsorbed?
thick ascending limb
What aid in the diffusion of Mg2+ through tight junctions in the TAL?
paracellin-1
What are the 2 cell types in the distal tubule and collecting duct?
intercalated cells
principle cells
What is special about principle cells in the distal tubule?
Na+ reabsorption stimulated by aldosterone
What transporter reabsorbs NaCl in the distal tubule?
thiazide-sensitive NaCl co-transporter
What is Gitelman Syndrome?
defective thiazide-sensitive NaCl co-transporter
less NaCl reabsorption = more concentrated urine
What is the Vte of principle cells in the collecting ducts and why?
-40 mV
ENac is pulling Na+ out of lumen
What transporter reabsorbs Na+ in principle cells of the collecting duct?
ENac (K+/Na+ channel)
How does Cl- get reabsorbs in principle cells of the collecting ducts?
paracellularly
- does not use ENac (K+/Na+ channel)
What is Liddle Syndrome?
increases ENac activity
causes more Na+ reabsorption and high BP
What is the Vte of beta-intercalated cells in the collecting duct and why?
-40 mV
HCO3- is being pumped into lumen via HCO3-/Cl- exchanger
What transporter do beta-intercalated cells use to transport Cl-?
HCO3-/Cl- exchanger
- aids in HCO3- secretion
Do beta-intercalated cells transport Na+?
no
only Cl-, HCO3-, H+
What is aldosterone’s affect on NaCl reabsorption?
increases
What cell type does K+ secretion in collecting duct?
principle cells (via ENac)
What cell type does K+ reabsorption in collecting duct/distal tubule?
alpha-intercalated cells (H+/K+ pump)
Why does hypokalemia induce acidosis?
K+ is reabsorbed by alpha-intercalated cell’s H+/K+ pump
If K+ is not being reabsorbed H+ is building up in blood
What cell type performs H+ secretion in the collecting duct/distal tubule?
alpha-intercalated cells (H+/K+ pump)
What cell type performs HCO3- secretion in the distal tubule?
beta-intercalated cells (HCO3-/Cl- exchanger)
What is the HCO3- pump and the H+ pump located on alpha-intercalated cells?
HCO3-: basolateral side
H+: apical side
What is the HCO3- pump and the H+ pump located on beta-intercalated cells?
HCO3-: apical side
H+: basolateral side
Ca2+ reabsorption is tightly regulated in the __________________ compared to the proximal tubule
distal convoluted tubule
What are 2 reasons kidneys excrete H+ into lumen?
- reabsorb filtered HCO3-
- excrete non-volatile acids
What’s the net uptake of acid in a day:
What’s the net metabolic acid produced in a day:
How much H+ is excreted in a day:
How much HCO3- is reabsorbed in a day:
30
55
70
4320
What are the 2 fates of H+ secreted in the lumen?
- make new HCO3- (combines with OH- to make water)
- secreted as a titratable acid
Is the HCO3 made in H+ excretion or HCO3- absorption considered “new”?
H+ excretion
Where is the most HCO3- reabsorbed?
proximal tubule
What 3 segments of the nephron participate in acid secretion?
- proximal tubule
- thick ascending limb
- cortical collecting duct
How does the early proximal tubule play a role in acid secretion?
Na/HCO3- exchanger
- HCO3- reabsorption
H+ secretion
How does the thick ascending limb play a role in acid secretion?
Na+/HCO3- exchanger
- HCO3- reabsorption
How does the cortical collecting duct play a role in acid secretion?
alpha/beta-intercalated cells
*H+/HCO3- secretion
Does glutamine breakdown or urea formation make new HCO3-?
glutamine breakdown
What 2 things are needed to make a concentrated urine?
- H2O permeable nephron segments
- hyper-osmotic medullary interstitum
What is the role of ADH?
increase water reabsorption by inserting more aquaporins
- more concentrated urine
What are 2 stimulators of ADH?
** 1. increased plasma osmolarity
2. decreased ECF
What 2 segments of the nephron are the most water permeable?
PT
tDLH
Where is ADH the most active?
inner medullary collecting duct
Where does ADH first appear?
distal tubule
What are the 2 steps to generating a hyperosmotic medullary interstitum?
- reabsorb H2O in tDLH
- reabsorb NaCl in TAL
What is the single effect of the counter-current loop?
movement of NaCl out of ascending limb increases the osmolarity of interstitum
What is the osmotic equillibrium of the counter-current loop?
entering fluid is isosmotic but turns hyperosmotic as water is reabsorbed in tDLH
What is the tubule flow of the counter-current loop?
concentrated fluid moves the LH tip which drives more NaCl into interstitum
What does the vasta cava do?
picks up NaCl from interstitum and drops it back off
urea concentration increases/decreases as you get deeper into the medulla
increases
Where is 50% of urea secretion?
tip of LH
Urea is reabsorbed in the presence of ________
ADH
ADH is release when water intake is high or low?
low
Why does urea build up in interstitum when ADH is present?
provides driving force for water reabsorption to hydrate body
In respiratory alkalosis compensation, which is larger…[HCO3]/[CO2]?
small/large
* needs to decrease CO2
In respiratory acidosis compensation, which is larger…[HCO3]/[CO2]?
large/small
* needs to increase CO2
In metabolic alkalosis compensation, which is larger…[HCO3]/[CO2]?
large/small
* needs to increase CO2
In metabolic acidosis compensation, which is larger…[HCO3]/[CO2]?
small/large
* needs to decrease CO2
Metabolic alkalosis…
pH:
[HCO3-]:
PCO2:
equation:
pH: increase
[HCO3-]: increase
PCO2: NA
equation: right
Metabolic acidosis…
pH:
[HCO3-]:
PCO2:
equation:
pH: decrease
[HCO3-]: decrease
PCO2: NA
equation: left
Respiratory alkalosis…
pH:
[HCO3-]:
PCO2:
equation:
pH: increase
[HCO3-]: decrease
PCO2: decrease
equation: left
Respiratory acidosis…
pH:
[HCO3-]:
PCO2:
equation:
pH: decrease
[HCO3-]: increase
PCO2: increase
equation: right
What’s the normal pH?
7.4
What’s the normal PCO2?
40
What’s the normal HCO3-?
24
What cells are affected by ADH?
principle cells
What is the difference between Cl- transport in the early vs late proximal tubule?
early: only paracellular
late: trans and paracellular
Is there water transport at the distal convoluted tubule?
What is reabsorbed there?
No
only Na, Cl, K+
Intercalated cells in the CCT only transport…
Cl-
HCO3-
H+
K+
What’s the role of the juxtaglomerular apparatus in kidney function?
contains masala dense and aids in tubuloglomerulus feedback (autoregulation)
What’s the effect of atrial natriuretic peptide (ANP) on the kidneys?
promotes sodium and water excretion, reducing blood volume and pressure
