Renal 3

Question 1

Of the 180L/day filtered what is excreted

Answer 1

less than 1% (1.5L)

Question 2

what does regulated reabsorption allow kidneys to do

Answer 2

selectively return ions and water to plasma and maintain homeostasis

Question 3

Why filter 180L if only excreting 1%

Answer 3

• rapid way to remove unwanted materials
• rapid regulation of fluid and ions

Question 4

what can be active and passive

Answer 4

reabsorption

Question 5

filtrate in lumen and ECF initially have what similar

Answer 5

solute, they are isosmotic

Question 6

reabsorption involves what two types of transport

Answer 6

transepithilial (transcellular)
paracellular

Question 7

transepithelial transport

Answer 7

substances cross the apical and basolateral membranes of tubule cells to enter ECF (require protein transporters)

Question 8

paracellular transport

Answer 8

substances pass through the cell to cell junctions between two adjacent tubule cells

Question 9

what creates the electrochemical gradient that drives reabsorption

Answer 9

reabsorption of sodium set up by Na-K ATPase

Question 10

what does sodium do

Answer 10

starts process of active transport that drives all reabsorption within proximal tubule

Question 11

what kind of transport is basolateral Na always

Answer 11

active transport via NA-K ATPase

Question 12

how does Na cause secondary active transport (symport with Na+)

Answer 12

Na moving down its electrochemical gradient pulls glucose, amino acids, ions into the cell against their concentration gradient

Question 13

What are two other reabsorption mechanisms

Answer 13

passive reabsorption, endocytosis

Question 14

passive reabsorption (e.g. urea)

Answer 14

initially urea=urea
when Na and anions move, H20 drawn via osmotic gradient and urea now has concentration gradieint to move via paracellular transport

Question 15

endocytosis

Answer 15

megalin binds to small plasma proteins and peptides to be digested by lyosomes in cell

Question 16

what do the majority of substances transported in the nephron use

Answer 16

membrane proteins

Question 17

what is saturation of these membrane proteins

Answer 17

max rate of transport that occurs when all available carrier are occupied

Question 18

what is the transport rate at saturation

Answer 18

transport maximum

Question 19

what happens when excess glucose is filtered

Answer 19

more glucose then transporter so glucose excreted

Question 20

renal threshold

Answer 20

plasma concentration of a solute when it first appears in the urine

Question 21

amount excreted =

Answer 21

Amount filtered - amount absorbed + amount secreted

Question 22

what is glucose appearing in urine called

Answer 22

glucosuria or glycosuria

Question 23

what causes the peritubular capillary pressures to favor reabsorpition

Answer 23

colloid osmotic gradient from protein witihin peritubular capillaries draws fluid and dissolved solutes to be reabsorbed

Question 24

what does the hydrostatic pressure drop to after fluid is removed and resistance encountered

Answer 24

10mmHg

Question 25

why does the oncotic pressure remain 30mmHg as blood travels to peritubular

Answer 25

plasma proteins are not filtered

Question 26

what is the net pressure that drives fluid and solutes from interstitial space back into capillaries

Answer 26

20mmHg 30-10

Question 27

what is secretion

Answer 27

transfer of molecules from ECF into lumen of nephron

Question 28

what does secretion depend on like reabsorption

Answer 28

membrane transport proteins

Question 29

what kind of process is secretion

Answer 29

active requiring movement of substances against concentration gradients

Question 30

purpose of secretion

Answer 30

homeostatic regulation of K+ and H+ (in distal) organic compound removal (medications, in proximal)

Question 31

what does secretion enhance

Answer 31

excretion of a substance

Question 32

when will excretion of a substance be very high

Answer 32

if filtered, not reabsorbed, and then secreted

Question 33

how are organic solutes secreted

Answer 33

multi step (tertiary) active transport (proximal tubule)

Question 34

what is tertiary active transport

Answer 34

indirect active ATP process is 3 steps removed from movement of the molecule of interest

Question 35

oat transporters

Answer 35

organic anion trasnporters

Question 36

where do OAT transporters use energy from for tertiary indirect active transport

Answer 36

transporting dicarboxylates down their concentration gradient to move organic anions against their concentration gradient

Question 37

what is a-ketoglutarate

Answer 37

by-product of citric acid cycle

Question 38

what is direct active transport (tertiary process)

Answer 38

Na-K-ATPase keeps Na in cell low

Question 39

what is secondary indirect active transport (tertiary process)

Answer 39

Na-dicarboxylate cotransporter concentrates a dicarboxylate in cell using energy from Na gradient

Question 40

prior to 1930s what was leading cause of death

Answer 40

infection

Question 41

why was all penicilin ingested be excreted within 3-4 hours

Answer 41

readily filtered and secreted using tertiary process

Question 42

what would penicillin be given with

Answer 42

probenecid which was preferentially secreted by OAT transporter and prevented penicillin secretion

Question 43

what does excretion tell us

Answer 43

only what body is eliminating, not renal function

Question 44

what is GFR an indicator of

Answer 44

overall kidney function

Question 45

what is renal handling/clearance info necessary for

Answer 45

new drugs

Question 46

how do we look directly at filtration, reabsorption, and secretion at level of individual nephron

Answer 46

experimentally indirect methods using analysis of urine and blood