Physio Exam 3 Renal 3

Front 1

Filtered Load Equation

Back 1

(GFR) [P]x

Front 2

Excretion Rate equation

Back 2

(V)u [U]x

Front 3

Filtered load in normal conditions is equal to

Back 3

Excretion Rate

Front 4

Reabsorption or Secretion Rate Equation

Back 4

(Filtered Load-Excretion Rate)
+=reabsorptio
-=secretion of substance plus something being added

Front 5

Some substances, like Ca2+ are not freely filtered why?

Back 5

because they are bound to plasma proteins

Front 6

Transcellular pathway

Back 6

substances goes through luminal membrane..through epithelial cell, goes either to either basal membrane into interstitial space or into lateral space betwee epithelial cells

Front 7

Paracellular

Back 7

move in between lateral spaces by diffusion. Its regulated by type of tight junctions. Tight junction become more complicated as we move across the nephron, the most leaky ones are on the proximal tubule the tighter ones are on the collecting tubules

Front 8

What regulates paracellular pathway?

Back 8

Tight Junctions

Front 9

Tight Junctions form zipper like structures by

Back 9

membrane proteinswith extracellular domain :claddin and occludin. They also have connections to the cytoskelton.

Front 10

Mutation in claudin-16 causes

Back 10

A disease caused Hypomagnesemia-
Hypercalciuria Syndrome by affecting
paracellular transport of calcium
and magnesium in thick ascending limb
of the loop of Henle

Front 11

Na sites of reabsorption

Back 11

67% in proximal convoluted tubule
25% Thick ascending limb
5% Distal convoluted tubule

Front 12

Site of Na reabsorption is site of action of

Back 12

many diuretics like "loop diuretics" at thick ascending loop
Thiazide diuretics at the distal convoluted tubule
K sparing diuretics at the conducting tubule

Front 13

Diuretics block

Back 13

Na transport and as a consequence H2O is lost

Front 14

Whats reabsorbed in the proximal tubule?

Back 14

100% Glucose
100% Amino Acids
85% HCO3-
Most Pi, lactate, citrate
Large amounts of Na+

Front 15

All of the transport mechanism on the proximal tubule dependent on

Back 15

Na/K Atpase on basolateral membrane..Na out K in…low levels of K inside epithelia, great [] gradient from lumen into epithelia cell..so all transport are secondary active transport even though they don’t use the ATP they needed it to function

Front 16

SGLT has two isoforoms in the proximal convoluted tubule

Back 16

SGLT 1 and 2 on apical membrane

Front 17

Once gluc inside the cell, it exits using

Back 17

Glut 2

Front 18

In the proximal tubule Carbonic Anhydrase converts HCO3 into CO2 and H+ and

Back 18

it is pumped into lumen via Na/H, HCO3 is free and reabsorbed into blood in a facilitated diffusion.

Front 19

Under normal conditions, SGLT takes care of all

Back 19

glucose in proximal tubule

Front 20

At concentrations less
than 200 mg/dL virtually
100% of glucose is

Back 20

reabsorbed and excretion
is 0

Front 21

Transport max (Tm) of glucose occurs
at about

Back 21

350 mg/dL.

Front 22

Glucose begins to be
excreted below

Back 22

Tm (ie. at
threshold) because of the
phenomenon of splay

Front 23

Mechanisms for splay
related to

Back 23

to relatively low
affinity of SGLT for glucose
and because of nephron
heterogeneity with respect
to Tm

Front 24

When saturation of SGLT occurs can lead to

Back 24

diabetes mellitus

Front 25

Transcellular reabsorption in late proximal tubule

Back 25

Early PT absorbs primarily Na+/HCO3-

Late PT absorbs
Primarily Na+/Cl-

Front 26

Paracellular Route in late proxima tubule

Back 26

Cl- moves down a
concentration gradient
through tight junctions

Cl- movement establishes a postive
transluminal potential

Na+ follows an electrical gradient

Front 27

The Na+ Concentration
in the lumen of the
nephron remains
relatively constant as
fluid moves along the
proximal tubule? why?

Back 27

Water movement
must be balanced
so that the Na+
concentration
remains constant

Front 28

Why does H2O follow Na?

Back 28

Na moves AA and Gluc Phosphate across lumen, osmolality of interstitial fluid increases, so an osmotic gradient is built up and drives water in (paracellulary or transcellularly)

Front 29

In the proximal tubule H2O is reabsobed via

Back 29

AQP1 on apical membrane.

Front 30

On basal membrane H2O exits through

Back 30

QP3/4

Front 31

is H2O readily regulated in the proximal tubule?

Back 31

No, because it just follows Na, regulation occurs on distal parts.

Front 32

Movement of water is also dependent on starling forces for reabsorption as blood moves through glomerulus (lots of filtration, no reabsorption) and enters paratubular capillaries lot of fluid loss, so

Back 32

lots of proteins trapped in these capillaries leading to high oncotic pressure which favors fluid reabsorption from interstitial fluid into these capillaries

Front 33

Glomerulotubular Balance refers to

Back 33

ensuring a constant return of fraction of filtered load in proximal tubule

Front 34

What if GFR was increased (doubled) what would happen to filtered load?

Back 34

filtered load increases,leads to increase in oncotic pressure and decrease in capillary pressure hence reabsorption gradient from interstitum into capillary would increase and reabsorption would increase.Glomerulotubular balance ensures that 60% of this now higher filtered load would come back into the plasma

Front 35

GGlomerulotubular balance when theres volume expansion

Back 35

Volume is greater in plasma, this decreases oncotic pressure in capillaries and increases hydrostatic pressure, leadinf to decrease in reabsorption

Front 36

Glomerulotubular balance when theres volume contraction

Back 36

: proteins in peritubulular capillaries would be increased and oncotic pressure would go up, pressure goes down and reabsoprtion occurs

Front 37

What would be the effect on reabsorption if during volume expansion, GFR is constant

Back 37

less
reabsorption of Na+ and
water occurs

Front 38

what happens to reabsorption if GFR is constant during volume contraction

Back 38

more reabsorption of Na and water occurs

Front 39

Protein reabsorption is returned as

Back 39

returned as the ultrafiltrate
passes along the proximal tubule

Front 40

All proteins that leaks in the nephron would be reabsorbed in proximal tubule. This relies on

Back 40

endocytosis. Clathrin coated pits on apical membrane of proximal tubules. Cubulin and megalin and they bind any of the proteins found in tubule fluid and trigger endocytosis

Front 41

Excessive Muscle cell breakdown could result in myoglobin found in plasma..why

Back 41

it would saturate endocytotic processes and myoglobin would end up in blood

Front 42

Why is secretion of organic anions and cations by proximal tubule important?

Back 42

because organic compounds are bond to plasma protein (it wont be filtered) so they need to be secreted somehow

Front 43

How are organic anions secreted?

Back 43

tertiary active transport: Na/K Atpase (Na gradient used) gradient used by NaDicarboxylic acid transporter which transports along with Na, alpha ketogluterate across basolateral membrane into cell. Alpha ketogluterate is exchanged with organic anions OAT1,2,3
(no need to know names of transporters)

Front 44

Organic Cations (creatine, epinephrine, NE) use

Back 44

use electrical gradient to move passively into cell or they can exit luminal side by OC/H+ antiporter or MDR1

Front 45

The thin descending loop
and thin ascending loop of
Henle are important in the

Back 45

counter
current multiplication mechanism
and urine concentration and dilution

Front 46

Thin Descending H2O and NaCl permeability

Back 46

H2O=Permeable
NaCl=Permeable

Front 47

Thin Ascending permeability to NaCl and H20
o

Back 47

NaCl permeable
H2O impermeable