phys -renal II

Question 1

1. in the proximal convoluted tubule, what % of what is filtered is reabsorbed?
2. how is this accomplished (what type junctions and what membranes)?

Answer 1

1. 65% of what is filtered is reabsorbed back into the blood by the PCT
2. tight leaky junctions which separate the apical and basolateral membranes

Question 2

1. how is the surface area of the apical membrane increased?
2. what is on the surface of these
3. what is this “border” called, why?

Answer 2

1. fingerlike microvilli increase surface area
2. on the surface of these is a sugar group called glycocalyx
3. called a brush border, because it looks like shrubbery

Question 3

what is the function of the brush border

Answer 3

enzymes become trapped in the bursh border (ex. apical carbonic anhydrase)

Question 4

there are alot of folds in the BL membrane, what is contained in the basolateral membrane folds

Answer 4

tons of mitochondria

Question 5

what is the difference in surface area between the proximal convoluted tubule and the loop of henle?

Answer 5

there are no or less folds in the loop of henle because it doesnt need the extra surface area.

Question 6

how much of the filtering does the DCT (distal convoluted tubule) do?

Answer 6

10-15%

Question 7

how much filtrate does the kidneys filter daily (in liters)?

2. how much of that becomes urine?
3. so ___ liters is reabsorbed

Answer 7

1. the kidneys filter 180 liters of filtrate daily
2. 2.5 liters becomes urine
3. 177.5 liters of filtrate is reabsorbed

Question 8

1. what does the PCT have on its membranes?

2. what does that do to the lytes and charges inside?

Answer 8

1. has alot on Na+/K+ pumps so

2. there is low sodium inside along with negatively charged protein

Question 9

1. in the apical region the sodium uses what to get in?

2. however what happens to it at the basolateral membrane?

Answer 9

1. in the apical membrane sodium is pumped in with a co-transporter (glucose or amino acid).
2. it is pumped out the back using Na+/K+ pumps (basolateram membrane)

Question 10

what is reabsorbed in the early PCT

Answer 10

glucose, amino acids, bicarb, (by moving sodium with co-transporters)

Question 11

what is “the load”

Answer 11

the load is when all glucose/ sodium co-transporters are occupied

Question 12

1. what is the maximum rate that somthing can be extracted by the body
2. what happens if this is exceeded

Answer 12

1. transport max or V-max

2. if v-max is exceeded, there is overflow

Question 13

what is the normal rate of glucose extraction?

Answer 13

125 mg/min

Question 14

1. what happens if your body were to have glucose coming down at 200 mg/min?
2. what is this rate of 200 mg/min called ?

Answer 14

1. your body could get most of it, but there would be there would start to be spillage of glucose into the urine
2. “threshold”

Question 15

what is 375 mg/min and why is there such a big range?

Answer 15

375 mg/min is transport max, the range is large because some nephrons are new, some old, some large and some small.

Question 16

1. what hormones can increase your glucose?

2. what is Dawn syndrome?

Answer 16

1. cortisol and growth hormone can increase blood glucose

2. Dawn syndrome is when your body releases growth hormone into your blood and your glucose shoots up

Question 17

At what point does reabsorption of glucose and amino acids cease?

Answer 17

once into the late proximal convoluted tubule

Question 18

1. what happens if glucose gets past the early PCT

2. how is this manifest in diabetics?

Answer 18

1. it becomes osmotically active

2. you see polyuria and polydipsia

Question 19

once all the solutes leave the filtrate, what follows (through what does it move), where does it go? and what are you left with?

Answer 19

once the solute leaves, water follows (thru the leaky junctions into the interstitial space) leaving urea behind.

Question 20

since the concentration gradient is against the filtrate once everything leaves and the urea is left, what does the urea do? what transport method?

Answer 20

the urea leaves the filtrate via passive transport

Question 21

how is active transport set up

Answer 21

via sodium/ potassium pumps

Question 22

how is secondary active transport done

Answer 22

via sodium/ glucose pumps (co-transporters)

Question 23

what are factors that change the effecicacy of passive reabsorption?

Answer 23

1. the concentration gradient
2. premeability of the substance thru the membrane or tight leaky junctions
3. residual time in the tubule (the longer it stays, the more time it has to move thru).

Question 24

how many strands on a tight leaky junction?

Answer 24

2

Question 25

1. what are the two types of carbonic anhydrase?

2. how are they different?

Answer 25

1. apical carbonic anhydrase (which is at the apical membrane’s brush border) and cytoplasmic carbonic anhydrase
   2a) apical joins bircarb and hydrogen to form carbonic acid to get it into the tubule. once inside, it breaks into H+ and Hco3-
   2b) cytoplasmic carbonic anhydrase re-joins the co2 and H20 to form carbonic acid which breaks down again retaining the bicarb and expelling the H+

Question 26

once the carbonic acid breaks down into HCO3- and H+, how do the convoluted tubules get rid of it and what happens to the bicarb (ahd what part of the PCT does this happen)?

Answer 26

the hydrogen is pumped out via H+ pumps

bicarb is exchanged (like in the bohr effect) for Cl- ion (in the late PCT)

Question 27

how is chloride pumped out of the filtrate?

Answer 27

via sodium/ chloride pumps (dual pumps) and chloride also follows the concentration gradient thru the tight leaky junctions (between cells)

Question 28

how does the body deal with calcium?

Answer 28

whatever happens to Na+, happens to Ca++

Question 29

osmolarity in the early PCT is 300 mOsm, what is it in the late PCT?

Answer 29

because even when solute is pulled out in a portion (65%), water will follow in a portion (65%); therefore, the osmolarity will remain 300 mOsm.

Question 30

what factors increase the absorption percentage (65%) in the PCT/

Answer 30

vasopressors such as angiotensin II, epi and nor epi

Question 31

what kind of cells are in the descending loop of henle?

Answer 31

simple squamous cells

Question 32

what kind of cells are in the thick ascending loop of henle?

Answer 32

cuboidal

Question 33

1.what is special about the space between the cells in the early PCT?

Answer 33

1. the space between the cells has concentrated solute

Question 34

1. how much of the urea is absorbed at the early PCT?

2. what is urea used for in humans?

Answer 34

1. 30%

2. it is used for osmolarity to keep serum osmo between 270-300

Question 35

what is different about the thick ascending limb and the descending limb (of the loop of henle)?

discuss the gradient that one creates and the osmolarity changes of the other

Answer 35

the descending limb has a high mOsm, it goes from 300 mOsm to 1200 mOsm at the bottom (becase you have lost alot of water).

the ascending limb is permeable to solutes (but not to water. solutes will leak out, creating a gradient that will pull water out of the descending limb (seems backward, but it creates a gradient for the next fluids)

Question 36

what is the NAME of the system that is created by solutes (sodium) being leaked out of the thick ascending limb of the loop of henle and the descending loop of henle losing water because of it?

Answer 36

counter current system

Question 37

what happens to the water that is pulled from the descending loop of henle?

Answer 37

the vasa recta absorbs it

Question 38

1. how much of the filtrate water is pulled out at the descending loop of henle?
2. that means ___% of salt/solutes is secreted from the thicck ascending loop of henle

Answer 38

1. 25%

2. 25%

Question 39

1. where in the loop of henle is urea reabsorbed?

2. how much is kept over by the body for osmolyte?

Answer 39

1. at the end of the descending and the beginning of the ascending (the thin ascending limb).
2. 50%

Question 40

1. how does lasix (a loop diuretic) work?

2. how does that make you diruese?

Answer 40

1. it blocks the Na+/K+/Cl- triple pump located in the thick loop of henle.
2. if you prevent the pumps from putting solute (Na+, K+, Cl-)out into the space to be picked up (absorbed) by the vasa recta, you will pee it out.

Question 41

what is special about the Na+/K+/Cl- (triple pump)?

Answer 41

it is a triple pump (thats different!!) and it prevents Ca++ from doing what sodium does (which calcium usually does what sodium does).

Question 42

there is alot of K+ inside the ascending loop of henle d/t potassium being pumped in, so what happens to the K+

Answer 42

the K+ drives all of the divalent (2++) ions out of the ascending loop …i.e. mag++, ca++

Question 43

what hormone controls the process of electrolyte exchange in the proximal and loop of henle?

Answer 43

parathyroid hormone

Question 44

as the vasa recta flows across the loop of henle, does it become hyper or hypo osmotic?

Answer 44

hypo-osmotic because it is absorbing all of the fluid that the descending loop of henle is releasing

Question 45

1. why is the thick loop of henle called the “diluting limb”?
2. what is the mOsm of the thick loop of henle?

Answer 45

1. because the ascending (thick) loop of henle is getting rid of all of the solutes that will create the salt gradient that will pull the fluid out of the descending loop of henle.
2. 150 mOsm

Question 46

what happens if there is too much acid in the cells of the kidneys

Answer 46

you can exchange H+ with a Na+/H+ exchanger that brings sodium into the cell and pushes H+ out of the cell.

Question 47

the JGA connects to what 2 structures?

Answer 47

JGA connectes between the afferent arteriole and the distal convoluted tubele

Question 48

1. where is the Macula Densa?

2. what does it do?

Answer 48

1. on the section of the distal convoluted tubule facing the Afferent Arteriole.
2. it samples the salt content of the filtrate and tells the grandular cells when to secrete renin (which will eventually constrict and change sodium flow).

Question 49

what happens if the macula densa samples the filtrate and the sodium is low

Answer 49

the macula densa “takes the brakes off” the granular cells and they secrete renin

Question 50

1. grandular cells are what type of intervention?

2. what other hormones do the grandular cells respond to (and under what circumstances)?

Answer 50

1. Grandular cells are beta 1
2. they respond to:
   a) epinephrine from the ardrenal cortex and to
   b) nor epi in the blood from post ganglionic sympathetic release

Question 51

1. what is the path of renin?

2. What vessel does Angiotensin II work on?

Answer 51

1. renin turns angiotensinogen(from liver) into angiotensin I. Angiotensin I goes to the lungs and is converted by Angiotensin converting Enzyme (ACE) into Angiotensin II …
2. which is the potent vasoconstrictor on the Efferent arteriole

Question 52

1. angiotensin works of the efferent arteriole to do what?

2. what hapens if that doesnt fix your sodium deficet?

Answer 52

1. angiotensin II constricts the efferent arteriole which increases GFR (reabsorption of Na+ in the PCT).
2. the adrenal cortex will secrete Aldosterone which to cause more reabsorption of sodium

Question 53

where does aldosterone work

Answer 53

on the late DCT

Question 54

1. what are the 2 cells in the late DCT and cortical collecting ducts?
2. what hormone affects them?

Answer 54

1a) principle cells (called principle because they make up 90%)
1b) intercalated cells
2. aldosterone works on these cells

Question 55

1. what does aldosterone cause to be exchanged or secreted?

2. what conditions cause aldosterone release?

Answer 55

1. aldosterone can cause an exchange between sodium and hydrogen or sodium and potassium
2. hyperkalemia can cause aldosterone secretion

Question 56

what do the primary cells do with aldosterone and what do the intercalating cells do with aldosterone

Answer 56

primary cells exchange sodium for H+ or K+ (pulls sodium in and kicks the others out)
intercalating cells get rid of H+ ions (deal only with acidosis and proton pumps)

Question 57

how do intercalating cells deal with H+

Answer 57

they have carbonic anhydrase in its cells which turns co2 and h20 int h2co3 which turns into HCO3- and H+.
the H+ is pumped out and the bicarb is exchanged for Cl-

Question 58

what is special about the medullary collectind ducts

Answer 58

they have aquaporins which react to ADH and move together to form water permeable tubules (because the protein coats cant cover the space between each tubule) which will leak water out of the collecting duct and back into the body.
without ADH, they stay far apart and a protein coat seals each individual tubule no water leaks out of collecting ducts and you urinate it out

Question 59

if you are dehydrated, your body will reabsorb water. what mOsm will your urine be?

Answer 59

1200 mOsm

Question 60

1. ADH aka___?
2. what kind of chemical/ hormone is it?
3. what kind of cell is it released from? where are they?
4. whak kind of cells do ADH work on?

Answer 60

1. ADH aka vasopressin
2. it is a neuropeptide (a protein released from neural tissue)-NOT A NEUROTRANSMITTER!!!
3. it is released from neuro-endocrine cells
4. made in hypothalamus and stored in posterior pituitary

Question 61

1. if you eat salty food , your body will reabsorb water. What does that have to do with ADH?
2. If you drink too much water, your body will want to get rid of water, what does ADH do with that?
3. what does ETOH do to ADH secretion?

Answer 61

1. if you have too much salt, you want to keep water so you secrete ADH
2. if you drink too much water, you need to get rid of water, so you dont secrete ADH
   3 etoh blocks ADH secretion so you pee

Question 62

when is filtrate considered urine?

Answer 62

at the end of the collecting duct.