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2 RENAL > Physiology 4 & 5 > Flashcards

Physiology 4 & 5 Flashcards

1
Q

where does most of tubular reabsorption occur

A

the proximal tubule of the nephron

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2
Q

why is tubular reabsorption necessary

A

because the kidneys filter 180 litres per day so without it we would pee out our plasma volume 65 times a day

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3
Q

what do the kidneys reabsorbed (important ones) (and percentages)

A 
99% of fluid 
99% of salt 
100% of glucose 
50% of urea 
0% of creatinine
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4
Q

why is reabsorption specific for different molecules

A

because it relies on specific transporter proteins for specific molecules

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5
Q

how much filtered fluid is reabsorbed in the proximal tubule

A

80ml/min

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6
Q

what substances are reabsorbed in the proximal tubule

A 
sugar 
amino acids 
phosphate 
sulphate 
lactate
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7
Q

what substances are secreted into the proximal tubule

A 
H+ ions 
Hippurates 
Neurotransmitters
Bile pigments 
Uric acid 
Drugs (atropine, morphine, penicillin) 
toxins
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8
Q

what is transcellular reabsorption

A

reabsorption which involves the molecule traveling through the epithelial cells of the tubule and out the other side into the interstitial fluid and then into the capillary

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9
Q

at what points does transcellular reabsorption need transporter proteins

A

between lumen of the tubule and the epithelial cell membrane

between the epithelial cell membrane and the interstitial fluid

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10
Q

what is paracellular reabsorption

A

when the molecule being absorbed travels through the gaps in between the epithelial cells

(depends on how tightly they cells are pushed together, some segments of the tubule are tighter than others)

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11
Q

what are the 3 types of carrier mediated membrane transport

A

primary active transport
secondary active transport
facilitated diffusion

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12
Q

what is primary active transport

A

when a transporter protein uses ATP to transport a molecule against its concentration gradient (Na/K pump)

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13
Q

what is secondary active transport

A

couples the movement of an ion (Na) down its concentration gradient with another ion needing moved

can be symport - same direction or antiport - opposite direction

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14
Q

what is facilitated diffusion

A

movement of a substrate down its existing concentration gradient

uses a transport protein instead of relying on diffusion across the membrane

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15
Q

what transport allows salt reabsorption in the proximal tubule

A

primary active transport with a Na/K pump

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16
Q

how is salt moved from the tubule into the blood

A

Na/k pump keeps the Na level inside the cell less than out in the insterstitial fluid

this concentration gradient is used to drive sodium out the capillary and into the cell

Na/k pump pumps it out of the cell into the interstitial fluid

this sets up an electrical gradient allowing Cl- ions and water to pass in paracellularly

oncotic drag then pulls the salt and water into the capillary

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17
Q

what route of reabsorption does water take out of the tubule and into the interstitial fluid

A

transcellular route following the concentration gradient set up by Na in the interstitial fluid

18
Q

what is oncotic drag

A

when the capillary is full of plasma proteins because it has lost all of its plasma to filtration it has a v high osmolarity

this causes it to pull salt and water out of the interstitial fluid in

19
Q

what transporter moves glucose in reabsorption

A

Glucose Na transporter - symporter (couples movement of glucose to sodium as it comes into the cell)

water then follows this paracellularly

water and glucose then pulled into the capillary via oncotic drag

20
Q

why is there glucose in the urine of diabetics

A

because when blood glucose is v high the the transport membranes become saturated and cannot reabsorb all the glucose coming through

it then passes through the tubules and is excreted in the urine

21
Q

what does para-aminohippurate acid (PAH) measure

A

renal plasma flow

22
Q

what is the cortico-medullary concentration gradient

A

a gradient that exists within the interstitial fluid - becoming more concentrated as you follow the loop of Henle down into the medulla

23
Q

what is the purpose of the cortico-medullary concentration gradient

A

to allow concentrated urine to be produced

24
Q

what allows juxtamedullary nephrons to produce more concentrated urine

A

their loop of Henle is longer so they are more exposed to the aortic-medullary concentration gradient

25
Q

what is reabsorbed in the descending limb of the loop of Henle

A

water

NOT SALT

26
Q

what is reabsorbed in the ascending limb of the look of Henle

A

SALT

not water

27
Q

what does the triple co-transporter on the luminal membrane of the ascending tubule do

A

moves Na, K and Cl ions from the tubular fluid into the epithelial cell

28
Q

what stops water from being absorbed in the ascending tubule

A

the epithelial cell junctions are too tight so it can’t cross paracellularly

29
Q

what happens to potassium ions than come into the epithelial cell via the triple co-transporter

A

some are recycles and put back into lumen

excess k and Cl move into interstitial fluid via K Cl transporter

30
Q

what do loop diuretics do

A

stop the activity of the triple co-transporter so stop salt reabsorption in the kidneys (so you have less salt and K in the blood)

31
Q

what causes water to leave the descending limb

A

the high osmolarity of the interstitial fluid caused by the NaCl from the ascending limb being pumped in?

32
Q

what happens to the interstitial fluid the further down the loop of Henle you go

A

it gets more concentrated

33
Q

What is the ideal concentration gradient between the ascending limb and the interstitial fluid

A

200 mili osmols

34
Q

how does the ascending limb achieve this gradient

A

by pumping out sodium into the interstitial fluid (as soon as new filtrate comes in)

35
Q

what does the descending limb do in response to the increases osmolarity of the interstitial fluid (due to the increase in salt put there by the ascending limb)

A

matches it by loosing water via osmosis

36
Q

in the steady state what is the highest concentration achieved by the cortico-medullary concentration gradient

A

1200 mili osmols

37
Q

What is the ideal concentration gradient between the ascending limb and the interstitial fluid

A

200 mili osmols

38
Q

how does the ascending limb achieve this gradient

A

by pumping out sodium into the interstitial fluid (as soon as new filtrate comes in)

39
Q

what does the descending limb do in response to the increases osmolarity of the interstitial fluid (due to the increase in salt put there by the ascending limb)

A

matches it by loosing water via osmosis

40
Q

in the steady state what is the highest concentration achieved by the cortico-medullary concentration gradient

A

1200 mili osmols

2 RENAL (20 decks)

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