Brainscape's Knowledge GenomeTM

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


See full index

GSSE pshysiology > renal physiology > Flashcards

renal physiology Flashcards

1
Q

Under normal conditions, by which route is the most water lost from the body?
And what other ways?

A

Urine (500 mL/day to 20 L/day)
Insensible 700 mL/day (skin 300–400, respiratory 300–400 mL/day)
Sweat (Variable)
Faeces ~200 mL/day.

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

What percentage of total body weight is water in a 70 kg male?

A

60%.

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

What are the different fluid compartments in the body? What ratio of total body water do they make up?

A 
Intracellular fluid (ICF) – 2/3
Extracellular fluid (ECF) – 1/3 (1/4 plasma, 3/4 interstitial fluid)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the transcellular fluid compartment?

A

Transcellular compartment is the component of extracellular water that lies
within epithelial lined spaces e.g. pleura, pericardium. It is around 1–2 L.

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

Does total body water vary proportionally or is it inversely proportional to fat?

A

Inversely proportional.
This is why women have a lower total body water percentage than men (55% vs
60%)

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

In regards to the ECF compartment; is the protein concentration greater in the
interstitial fluid or the plasma?

A

The protein concentration is higher in the plasma. This is because the capillaries
have a low permeability to the plasma proteins.

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

What ions have the highest concentration in the ICF and ECF?

A

Intracellular- Potassium and Phosphate

Extracellular- Sodium and Chloride and HCO3

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

How can intracellular fluid volume be calculated?

A

It cannot be measured directly.
It can be derived by measuring the volume of total body water and subtracting
the volume of the extracellular fluid.

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

why does plasma have more cations?

A

they are are attracted to the negatively

charged proteins in plasma

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

what is total body osmolarity?

A

Total body osmolarity is ~300 mOsm/L.

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

What percentage of the filtered load of water is reabsorbed in the proximal
tubule?

A

~70%.
The GFR is 125 mL/min, this means that 180 L of water is filtered a day. 70% of
this is reabsorbed in the proximal tubule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the most important carrier protein in the ascending limb of the Loop of
Henle?

A

NaK2Cl.
This is powered by secondary active transport. The basolateral Na/K ATPase
decreases the intracellular concentration of Na+. This allows for the Na+ to diffuse
out of the tubular fluid down its concentration gradient. It carries the other ions
with it as it does so.
This is blocked by Frusemide.

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

What part of the Loop of Henle is permeable to water?

A

the thin desending loop

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

What is the most important transport protein in the distal convoluted tubule?

A

It is the NaCl co-transporter.
This is powered by the basolateral Na/K ATPase, which sets up a concentration
gradient for Na+. This allows Na+ and Cl− transport through the luminal aspect
via the NaCl co transporter.
This is blocked by thiazide diuretics.

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

What is the function of the intercalated cells of the distal and collecting tubules?

A

Intercalated cells reabsorb K+ ions and HCO3
− while secreting H+ ions. The H+ is
secreted by the H+ ATPase (plays an integral part of acid regulation).

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

Which cell does Aldosterone act on?

A

The principal cells of the distal tubule and collecting duct.

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

what happens to the osmalarity of fluid goes along the PCT

A

The osmolarity stays the same along the PCT as water is absorbed along with the
solutes

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

which type of loop of henle is most prolific?

A

There are two types of LoH; cortical (85%) and juxtamedullary (15%) depending on how far they descend into the medulla.

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

which part of the nephron is in close connection with the macula densa?

A

the DCT

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

the collecting tubules form to create?

A

The collecting tubules coalesce to form collecting ducts.

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

are collecting ducts permeable to urea?

A

Collecting ducts are also permeable to urea, this helps to raise the osmolarity in
the medulla

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

What principle can be applied when measuring renal blood flow (RBF)?

A

Fick’s principle. This is equal to the amount of the substance taken up per unit
time divided by the arterio-venous difference.

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

What substance is used to calculate RBF, why is this substance used?

A

Para-aminohippuric acid. This is used as it is filtered at the glomerulus and then
secreted into the tubule, but not reabsorbed.

24
Q

What effect does noradrenaline have on renal blood flow?

A

It decreases RBF. It constricts both the afferent and efferent arterioles.

25
Q

Where is the macula densa found?

A

This is found at the confluence of the thick ascending limb of Loop of Henle and
DCT. It lies in close proximity to the afferent arteriole

26
Q

How does Tubuloglomerular feedback work to alter RBF?

A

This helps to auto regulate the delivery of blood to the glomerulus, based upon
the composition of the filtrate reaching the DCT.
In situations of high Na+ (and water) in the tubular fluid, the macula densa, located
in the distal convoluted tubule, will absorb Na+ through the luminal NaK2Cl
channel. This is then pumped out of the basolateral side by the Na/K ATPase, in
doing so adenosine is produced. The adenosine then binds to the adenosine A1
receptor on the afferent arteriole. This increases the intracellular concentration of
Ca2+ and causes vasoconstriction, therefore decreasing the RBF. The converse is
true when there is a low concentration of Na+ reaching the DCT.

27
Q

Using Fick’s principle, what is used to calculate GFR?

A

Inulin. This is because it is freely filtered in the glomerulus, but not secreted or
reabsorbed.

28
Q

Why is Creatinine used to calculate the eGFR?

A

This is because it is an endogenous product, produced during muscle metabolism. Unlike inulin, it is secreted into the tubules, so using it to calculate the
eGFR will slightly overestimate the eGFR.

29
Q

What are the determinants of the GFR?

A

Kf= glomerular ultra filtration coefficient
PGC = mean hydrostatic pressure in the glomerular capillaries
PT = mean hydrostatic pressure in the tubule (Bowman’s space)
πGC = oncotic pressure of the plasma in the glomerular capillaries
πT = oncotic pressure in the filtrate of the tubule
The kidneys are well set up for filtration as they have high Kf and a high hydrostatic pressure as the capillaries lie between two arterioles.

30
Q

what are 4 agents which cause relaxationof mesangial cells?

A

prostaglandin E class
dopamine
ANP
cAMP

31
Q

which mediators cause a contraction of mesangial cells ?

A 
prostaglandins F class
histamine
endotheliens
angiotensin 2
vasopressin 
NA
platelet activating factor and platelet derived growth factor 
thromboxane A2 
leukotrienes
32
Q

What two stimuli are the most important factors leading to release of aldosterone

A

Hyperkalaemia and Angiotensin II.

33
Q

Where in the kidney does Aldosterone act?

A

It works in the DCT + CT. It increases the activity of Na/K ATPase on the basolateral side as well as the luminal transport of Na, through insertion of eNaC channels. It acts to increase the reabsorption of Na+ and the secretion of K+ and H+.

34
Q

What is the range of urine osmolarity?

A

50–1200 mOsm/L. This is dependent on the presence of ADH.

35
Q

Where is renin released from?

A

Renin is released from the granular cells in the juxtaglomerular apparatus near
the afferent arteriole. It is released in response to decreased arteriolar wall tension, SNS stimulation and decreased Na+ or Cl−.

36
Q

What does anti-diuretic hormone (ADH) do?

A

It allows for the reabsorption of water in the late distal tubules, collecting tubules,
and collecting ducts. ADH binds to specific V2 receptors and increases the number of aquaporin-2 (AQP-2) in the luminal cell membrane. The molecules of
AQP-2, which are found in intracellular vesicles, cluster together and fuse withthe cell membrane by exocytosis. They form water channels that permit rapid
diffusion of water through the cells.

37
Q

How does Frusemide work?

A

It is a loop diuretic which prevents the action of NaK2Cl in the LoH.

38
Q

when the SNS reduced blood flow does the eGFR reduce?

A

conserved GFR.
NA released from the SNS, binds to α1 adrenoreceptors to cause vasoconstriction
of both the afferent and efferent arterioles. This results in a significantly reduced
renal blood flow. However, glomerular perfusion pressure is maintained due to
greater constriction of the efferent arterioles. Overall the GFR only drops a small
amount.

39
Q

Renin — This is secreted from the______ cells

A

Renin — This is secreted from the ‘granular’ cells

40
Q

when is renin released?

A

in response to decreased afferent
arteriole wall tension,
SNS activity acting on β1 adrenoreceptors,
prostaglandins or
decreased Na+ and Cl− delivery to the macula densa.
This is released in the blood
stream.

41
Q

what does renin activate ?

A

Angiotensinogen – Renin is an enzyme, which converts angiotensinogen to
angiotensin I.

42
Q

what is an example fo on osmotic diuretic?

A

mannitol?

43
Q

spironolactone is what type of diuretic?

A

Aldosterone antagonist. e.g. SpironolactoneInhibits that action of aldosterone in the DCT + collecting tubules.

44
Q

How is HCO3

− handled in the kidney (filtered, secreted or reabsorbed)

A

HCO3
− is freely filtered at the glomerulus and then reabsorbed along the collecting
system (usually near 100% is reabsorbed).

45
Q

Explain why the pH of the proximal tubules can not exceed pH 6.7, but in the
distal collecting duct and collecting tubules the pH can get as low as 4.5.

A

In the proximal tubules, the secretion of H+ is via secondary active transport.
Where as in the latter tubules the H+ is actively secreted by the H+ ATPase and
this can pump against a high concentration gradient.

46
Q

What is the most important urinary buffer?

A

Phosphate is most important in the kidneys. This is for two reasons; (1) phosphate is poorly reabsorbed so concentration increases in the tubular lumen,
thereby increasing the buffering (2) the pH in tubular fluid has a lower pH than
blood, so it is closer to phosphate pKa of 6.8.

47
Q

How is ammonia formed in the kidney?

A

This is by the metabolism of glutamine. Glutamine is converted to 2× HCO3
− and
2× NH4
+. This NH4
+ is secreted into the tubule and the HCO3
− is free to diffuse
into the blood stream.

48
Q

How is Na+ absorbed from the proximal tubule?

A

This is by secondary active transport. The Na/K ATPase on the basolateral
membrane decreases the intracellular concentration of Na and allows for passive diffusion of luminal Na+ down its concentration gradient. Many other
substances are absorbed via co-transport with Na e.g. glucose and amino
acids. 65% of filtered Na+ is absorbed here.

49
Q

How is Na+ handled in the Loop of Henle?

A

There are two channels in the ascending LoH. The NaK2Cl channel and the
Na–H anti-porter.
Remember that the descending limb of LoH is permeable to water, but relatively
impermeable to ions.

50
Q

How is HCO3

− absorbed from the proximal tubule?

A

This is via a rather convoluted pathway. H+ is secreted into the tublular lumen via
the Na/H+ anti-porter in the PCT. The H+ in the tubular lumen combines with the
HCO3
−, to form H2O and CO2. This CO2 diffuses back into the cell, combines
with H2O and then H+ and HCO3
− is formed. The HCO3
− concentration increases
and then HCO3
− diffuses out of the basolateral aspect of the cell, leaving the H+
to be secreted via the process described above.

51
Q

How do principal cells handle Na?

A

Principal cells absorb Na from the tubular lumen, under the control of Aldosterone.
Basolateral Na/K ATPase maintains a low Na+ concentration inside the cell and,
therefore, favors Na+ diffusion into the cell through special transport proteins.

52
Q

What pH can the urine be concentrated to?

A

pH 4.5. Can be secreted against a concentration gradient until a urine pH of
approximately 4.5. This is achieved by the intercalated cells

53
Q

when Na is resorbed in the PCT what else is it coabsorbed with?

A

glucose and amino acids

54
Q

in the second half of the nephron Na is coupled with the absorption of what?

A

chloride

55
Q

which glucose transporter is in the apical membrane on the kidney?

A

the SGLT 2

56
Q

what is the name of the transporter ont he basolateral surface of the renal tubule cell?

A

GLUT2

GSSE pshysiology (5 decks)

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