Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology III - Freedman > Unit 4: Renal Physiology: PART TWO: Reabsorption and Secretion > Flashcards

Unit 4: Renal Physiology: PART TWO: Reabsorption and Secretion Flashcards

1
Q

What is the Glomerular Filtration rate?

A

180 L/ day = 125 mL/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two ways to get ride of stuff through the kidney?

A
  1. Filtration–> and do NOT reabsorb it

2. Secretion (from blood in peritubular capillaries into where filtered stuff went too)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the amount of a substance filtered across the glomerular called?

A

the filtered load

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is occurring during filtration?

A

an interstitial like fluid is filtered across the glomerular cap into Bowman’s space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does the Filtered Load equal?

A

= GFR x plamsa conc. of substance X x % unbound in plasma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does the Filtration Fraction equal?

A

= GFR / RPF

the fraction of renal plasma flow that is filtered across the glomerular capillaries
- normally is 20% (.2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the fraction of renal plasma flow that is filtered across the glomerular capillaries? What is it normally?

A

Filtered Fraction

normally is .2 (20%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does the excretion rate equal?

A

urine flow x conc. of substance X in urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does Reabsorption or secretion rate = ?

A

= Filtered Load - excretion rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the fluid in Bowman’s Space and lumen of a nephron called?

A

tubular fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What sort of things are reabsorbed?

A
  • water
  • Na+
  • Cl-
  • HCO3-
  • glucose
  • AAs
  • urea
  • Ca++
  • Mg++
  • phosphate
  • lactate
  • citrate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the mechanism for reabsorption?

A

transporters in membrane of tubular epithelial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the MOST important function of the kidney? Why?

A

reabsorption of Na+–> b/c it is linked to ALL other reabsorption and virtually drives all resabsorption in the kidney!!!!*

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the major cation in the ECF?

A

Na+ (plasma and interstitial fluid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does the amount of Na+ in ECF influence?

A

influences ECF volume–> influencing plasma volume, blood volume, and BP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How much of sodium is reabsorped?

A

output = intake

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens if we increase the intake of Na+?

A

volume expansion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What substances are SECRETED from peritubular blood into the tubular fluid via the tubular epithelium?

A

organic acids, organic bases, K+

Secretion–> is an additional mechanism fro excreting substance into the urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What refers to the amount of substance excreted per unit of time?

A

Excretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is excretion the net result of?

A

Excretion = filtration - reabsorption + secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What can we compare excretion rate to in order to determine if a substance has been reabsorbed or secreted?

A

compare to Filtrated Load

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the equation for Excretion Rate? What is it for Filtered Load?

A

Excretion rate = urine flow x urine conc. of substance X

Filtered Load = GFR x plasma conc. of substance X

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What if the filtered load is greater than the excretion rate? What substance is this an example of?

A

= net reabsorption

Ex: Na+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What if the filtered load is less than the excretion rate? What substance is this an example of?

A

= net secretion

Ex: PAH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the two ways needed to get glucose reabsorbed and then transported into peritubular blood?

A

in early Proximal Tubule by Carrier-Mediated mechanisms (along with Na+)

  1. “SGLT”–> Secondary Active Transport (from tubular fluid into cell)
  2. GLUT 1 and GLUT 2–> Facilitate Diffusion (from cell into peritubular blood)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What type of transporter is used for glucose absorption, to get it from the tubular fluid into the tubular cell? What is moving uphill vs downhill? What other pump is necessary for this to occur?

A

Na+ glucose cotransporter (symporter) called “SGLT” (Sodium Glucose linked Transporter)

2 Na+ and 1 glucose

  • glucose moves uphill
  • Na+ moves downhill

Secondary Active Transport–>Uses:
Na+/K+ pump on peritubular capillary side keeps Na+ low in ECF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How is glucose transported from the tubular cell into the peritubular capillary?

A

via Facilitated Diffusion

  • moving DOWN conc. gradient
  • no energy needed
  • GLUT 1 and GLUT 2 (= insulin independent)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the filtered load for Glucose? What happens as plasma conc. of glucose increases?

A

glucose is freely filtered

Filtered Load = GFR x Plasma conc. of glucose

filtered load increases linearly

29
Q

At what plasma concentration is all glucose reabsorbed?

A

less than 200 mg/dl

all glucose can be reabsorbed

30
Q

At what plasma concentration does “splay” occur with glucose reabsorption? What is “splay”?

A

greater than 200 mg/dl, but less than 350 mg/dl

splay = bending of reabsorption curve–> a threshold where not all glucose is reabsorbed

reabsorption is approaching saturation

31
Q

What are two reasons for “splay” to occur for glucose titration curve?

A
  1. Low affinity of Na+ glucose cotransporter (glucose detaches and is excreted; few remaining binding sites near Tm)
  2. Heterogeneity of nephrons (some have higher Tm, some have lower; some glucose excreted before average Tm is reached)
32
Q

At what plasma glucose concentration is Tm reached? What occurs here on the titration curve?

A

greater than 350 mg/dl

glucose carries fully saturated and reabsorption of glucose flattens out

33
Q

At what plasma glucose conc. does excretion of glucose occur? When does excretion follow a linear increase as there is an increase in filtered load?

A

beings when it is greater than 200 mg/dl (hit threshold)

greater than 350 mg/dl

34
Q

What is the term for glucose in the urine? What three things could this be due to?

A

Glucosuria; Due to:

  1. High plasma glucose (>200mg/dl); diabetes
  2. Pregnancy (increased GFR which increases filtered load–> may spill some glucose into urine)
  3. Congenital abnormalities of Na+-glucose cotransporter
35
Q

Is urea freely filtered across the glomerular capillaries? How is it secreted or reabsorbed?

A

yes; and it is transported in most segments of the nephron

secreted or reabsorbed by diffusion (simple or facilitated)

36
Q

How is the secretion or reabsorption rate of Urea determined?

A

concentration gradient and permeability

37
Q

What happens to urea concentration in the tubular fluid as water is reabsorbed from the tubule? What does this create?

A

urea conc. increases–> creates a conc. gradient driving reabsorption of Urea

38
Q

T/F. Urea does not follow water reabsorption

A

False— urea does follow water reabsorption

39
Q

Where is 50% of Urea reabsorbed? And by what type of transport?

A

50% reabsorbed in Proximal Tubule via simple diffusion

40
Q

Where is urea secreted in the nephron? Is more or less of urea secreted than what was previous reabsorbed in the Proximal Tubule?

A

in the thin descending limb–> due to high conc. in interstitial fluid in inner medulla

MORE secreted than previously reabsorbed in Proximal tubule

41
Q

What parts of the nephron are impermeable to urea? What occurs here under the influence of ADH?

A
  • Thick ascending limb
  • distal tubule
  • cortical collecting duct
  • outer medullary collecting duct

ADH–> will stimulate water reabsorption here and therefore Urea is left behind (increase urea conc. in tubule fluid)

42
Q

What is the total filtered load for Urea? Of that, what is reabsorbed? What is excreted?

A

110% filtered load

  • 70% reabsorbed
  • 40% excreted
43
Q

After urea has traveled through the Loop of Henle, where is is reabsorbed? By what transporter?

A

Inner Medullary collecting duct–> by Urea Transporter 1

44
Q

What activates the Urea Transporter 1? Where is this located? And what is it doing?

A

ADH activates it; in inner medullary collecting ducts

Facilitated diffusion from tubular lumen–> ISF
70% of filtered load reabsorbed –the other 40% is excreted

45
Q

Can urea to toxic?

A

yes, at high levels

46
Q

What does the Urea recycling that occurs in the nephron cause? And therefore what does it help with?

A

causes buildup of high urea concentration in inner medulla–> creating osmotic gradient at Loop of Henle so water can be reabsorbed

47
Q

What substance is an example of secretion and is used to measure renal plasma flow?

A

PAH (para-aminohippuric acid)

RPF = to clearance of PAH

48
Q

Of the filtered load for PAH, what percentage is filterable and what isn’t and why?

A

10% filterable

90% not filterable b/c bound to plasma proteins

49
Q

Where is PAH secreted in the nephron? What happens when Tm is reached?

A

Proximal Tubules in peritubular membranes by transporters

Tm is reach and secretion is maxed out

50
Q

What happens to excretion of PAH as unbound plasma conc. of PAH increases?

A

excretion rises sharply and BOTH filtration and secretion are increased

51
Q

Once Tm is reached for PAH, what happens to excretion and filtered load?

A

rise in excretion parallels an increase in filtered load

52
Q

What does excretion equal for PAH?

A

= sum of filtration + secretion (as non is reabsorbed)

53
Q

What inhibits the secretion of PAH by transporters in peritubular membranes of Proximal Tubular cells?

A

probenecid

54
Q

What happens once the PAH transporters have hit maximum secretion? What then occurs with an increase in filtration?

A

filtration and excretion are parallel

and increase filtration results in an increase excretion

55
Q

What are the two forms that many substances secreted by the Proximal Tubule exist in?

A

(many substances are weak acids and weak bases)

  1. charged and uncharged
  2. relative amounts depend on pH
56
Q

What are examples of weak acids?

What are examples of weak bases?

A

PAH and salicylic acid (aspirin)

quinine, morphine

57
Q

When it comes to charges, what is the acid form of a weak acid? What is the conjugate base form?

How does the charge effect reabsorption?

A

acid form = HA (uncharged)
- can be pulled back

conjugate base form = A- (charged)
- can NOT be pulled back and is secreted

58
Q

At a low pH, what form of a weak acid will predominate?

A

the HA (acid form) predominates–> therefore can reabsorb easier

59
Q

At a high pH, what form of a weak acid will predominate?

A

the A- (conjugate base) form predominates–> can excrete more readily

60
Q

If we want to excrete an acid, will we want to increase or decrease the pH?

A

increase the pH or urine –> therefore it will be in the A- form and cannot be reabsorbed

61
Q

What is the base form and the conjugate acid form for a weak base?

A

base form = B (uncharged)
- pull back easier

conjugate acid form = BH+ (charged)
- cannot be pulled back and is excreted

62
Q

At a high pH, what form of a weak base predominates?

A

the B form (base form) –> can reabsorb easier

63
Q

At a low pH, what form of a weak base predominates?

A

BH+ form (conjugate acid)–> therefore can excrete

64
Q

If we want to excrete a base, what do we want to pH of urine to be, high or low?

A

want pH to be low–> therefore will be in conjugate acid form (BH+)–> making it charged and therefore cannot be reabsorbed and will be secreted

65
Q

What substances can diffuse across the tubular cells and therefore can be reabsorbed?*

A

the UNcharged substances

charged forms are excreted

66
Q

At a high pH what are we excreting, weak acid or weak base? What about at a low pH?

A

high pH–> excretion of weak acid

low pH–> excretion of weak base

67
Q

What are the two forms of Aspirin and which has a charge? Which can be reabsorbed and which cannot?

A

salicylic acid = HA form
- can be reabsorbed

salicylate = A- form
- cannot be reabsorbed

68
Q

If someone has an aspirin overdose, what do we want to do to maximize the loss of it?

A

put it in charged form–> so want to put it at a high pH, therefore it would be in the A- form (salicylate)

Physiology III - Freedman (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions