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Physiology III Final Exam > Urine Reabsorption > Flashcards

Urine Reabsorption Flashcards

1
Q

What is the “formula” for what makes up urine?

A

Glomerular filtration - tubular reabsorption + tubular secretion

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2
Q

What measurement is more vital for determining excretion rate?

A

Tubular reabsorption

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3
Q

Secretion of urine plays a role in the excretion of what ions in the urine?

A

Potassium and hydrogen ions

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4
Q

What is the general calculation of filtration for substances freely filtered and not bound to plasma proteins?

A

Glomerular filtration rate (GFR) X plasma concentration

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5
Q

How would we find the filtration of glucose per day, for example?

A

180 L/day (glomerular filtration) X 1 g/L (plasma concentration) = 180 g/day of glucose

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6
Q

Which is highly selective: tubular reabsorption or glomerular filtration?

A

Tubular reabsorption

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7
Q

Which is nonselective (except protein and substances bound to them): tubular reabsorption or glomerular filtration?

A

Glomerular filtration

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8
Q

Do the kidneys excrete all substances at the same rate?

A

No, everything individually based on the body’s needs

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9
Q

What are the four steps of the tubular reabsorption of a substance?

A

1 transportation across tubular epithelial membrane
2 goes through interstitial fluid
3 goes through peritubular capillary membrane
4 goes into the blood

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10
Q

What is the transcellular route in which water and solutes can travel through the tubular epithelium?

A

Through the cell membranes

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11
Q

What is the paracellular route in which water and solutes travel through the tubular epithelium?

A

Between the cells through tight junctions

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12
Q

How do water and solutes travel through the tubular epithelium via bulk flow/ultrafiltration which is mediated by hydrostatic pressure and osmotic flow?

A

Through peritubular capillary walls into the blood

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13
Q

How else can water and solutes travel through the tubular epithelium besides the transcellular and paracellular routes and through the peritubular capillary walls?

A

Through medullary interstitium fluid

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14
Q

Which form of active transport is coupled which hydrolysis of ATP?

A

Primary active transport

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15
Q

The sodium-potassium ATPase pump is an example of what kind of transport?

A

Primary active transport

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16
Q

What kind of active transport is coupled indirectly to the energy source like an ion gradient?

A

Secondary active transport

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17
Q

Reabsorption of glucose by the renal tubule is an example of what kind of transport?

A

Secondary active transport

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18
Q

Is water always absorbed by an active or passive mechanism? What is that mechanism?

A

Passive; osmosis

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19
Q

What is osmosis?

A

Diffusion of water from an area of low solute concentration to an area of high solute concentration

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20
Q

Where does the sodium transport system occur?

A

Proximal tubular membrane

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21
Q

Where is the sodium-potassium ATPase system located on the cell?

A

Cell membrane on the basolateral surface

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22
Q

What causes the -70 millivolt negative charge in the cell?

A

Active transport of sodium and potassium from inside the cell to the interstitium

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23
Q

Is the movement of sodium to the peritubular capillary from the intercellular fluid an active or passive process?

A

Passive (driven by osmotic gradient just like water)

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24
Q

What is the mechanism of transport of sodium from the lumen to tubular cell?

A

Diffusion

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25
Q

What is the mechanism of transport of sodium from the tubular cell to the interstitial fluid?

A

ATPase pump (active transport)

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26
Q

What is the mechanism of transport of sodium from the interstitial fluid to the peritubular capillary?

A

Diffusion

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27
Q

In what kind of transport are 2 or more substances transported across a membrane by a carrier molecule?

A

Secondary active transport

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28
Q

Sodium diffusing down its electrochemical gradient and that energy driving glucose (for example) down ITS electrochemical gradient would be an example of what kind of transport?

A

Secondary active transport

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29
Q

Where are the sodium glucose co-transporters located (SGLT2 and SGLT1)?

A

Brush border

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30
Q

What transporters are used to transport glucose into the cell against a concentration gradient (secondary active transport)?

A

SGLT2 and SGLT1

31
Q

Which SGLT is located in the early part of the proximal tubule?

A

SGLT2

32
Q

Which SGLT is located in the later part of the proximal tubule?

A

SGLT1

33
Q

Which SGLT transports 90% of the filtered glucose for reabsorption?

A

SGLT2

34
Q

Which SGLT transport 10% of the filtered glucose for reabsorption?

A

SGLT1

35
Q

What kind of transport is responsible for the transport of glucose from the proximal tubule across the luminal membrane?

A

Secondary active transport (usually via SGLT 2)

36
Q

What is responsible for the passive uptake of glucose into the peritubular capillary?

A

Bulk flow

37
Q

What is counter transport?

A

Secretion of substance into the tubule by secondary active transport

38
Q

What effect does sodium being actively transported into the cell have on hydrogen ions?

A

Drives hydrogen ions out of the cell into the tubular lumen (counter transport due to energy liberated from prior sodium transport)

39
Q

What is transport maximum?

A

Limit to the rate at which a solute can be transported during active reabsorption or secretion

40
Q

What is the overall average transport maximum for glucose?

A

375 mg/min (reached when all nephrons have reached their maximal capacity to reabsorb glucose)

41
Q

What effect does aging have on transport maximum and why?

A

Decreased because nephrons die with age (presence of kidney conditions more prevalent in older individuals)

42
Q

During what circumstance can some substances not demonstrate a transport maximum?

A

If absorbed passively

43
Q

What three things does the rate of transport depend on?

A

Electrochemical gradient
Permeability of membrane to substance
Time the fluid containing the substance remains in tubule

44
Q

What is the term for the type of transport where substances are passively absorbed and depend on other circumstances like electrochemical gradient, time substance-filled fluid remains in tubule, and membrane permeability?

A

Gradient-time transport

45
Q

What effect does aging have on gradient-time transport?

A

Increased

46
Q

Can actively transported substances exhibit characteristics of gradient-time transport?

A

Yes; example would be sodium reabsorption int he proximal tubule where sodium doesn’t have a transport maximum

47
Q

What is the pathway for urine flow structure by structure?

A

Nephron –> collecting ducts –> renal calyces –> ureters –> bladder

48
Q

What activity forces urine from the kidneys to the bladder and where does it occur?

A

Peristaltic contractions; renal pelvis and ureters

49
Q

What are the ureters made of?

A

Smooth visceral muscle

50
Q

What is the effect of parasympathetic stimulation on the ureters? Sympathetic?

A

Parasympathetic - increased contractions

Sympathetic - decreased contractions

51
Q

In what kind of situation does the ureterorenal reflex occur?

A

Painful ones, like a kidney stone

52
Q

Do the ureters contain pain fibers?

A

Yes, many

53
Q

What is the term for the process of the urinary bladder emptying when it is filled?

A

Micturition

54
Q

What is unique about the series of contractions during micturition?

A

Self-regenerative: initial contraction of detrusor muscle causes further activation of stretch receptors to lead to more contraction and repetition

55
Q

Urination can be facilitated or inhibited by what neurological brain centers?

A

Pons and cerebral cortex

56
Q

What muscles are contracted during voluntary urination?

A

Abdominal muscles

57
Q

What does the rate of back leakage of sodium in tubular reabsorption depend on?

A

Permeability of the tight junction

Rate of bulk flow reabsorption into the peritubular capillaries

58
Q

As the concentration of sodium in the proximal tubule increases, how is the reabsorption rate of sodium affected?

A

Also increases

59
Q

Sodium transport in the proximal tubules obey the principles of which transport concept?

A

Gradient time transport

60
Q

What kind of flow rate of tubular fluid exerts a greater amount of sodium being reabsorbed?

A

Slower flow rate

61
Q

What other absorption function is coupled with sodium reabsorption in the tubules?

A

Passive water absorption

62
Q

How is water absorbed passively at the same time as sodium reabsorption?

A

Osmosis occurs between highly permeable cells of the proximal tubule

63
Q

What effect does the osmosis of water in the proximal tubules on solutes?

A

Solvent drag occurs and the movement of water carries the solutes with it

64
Q

What kind of transport moves chloride from the negatively charged tubular lumen?

A

Passive

65
Q

What kind of transport moves chloride and sodium across the tubular membrane?

A

Secondary active transport (co-transport)

66
Q

What happens to urea concentration as water is reabsorbed?

A

Increases (causes passive reabsorption of urea)

67
Q

Where are urea transporters found?

A

Medullary collecting duct

68
Q

Is the proximal tubule very permeable to urea?

A

Not really

69
Q

Why is it important that the tubule NOT be very permeable to urea?

A

Allows for large amounts of urea to be excreted

70
Q

Where is 65% of the filtered water and sodium reabsorbed?

A

Proximal tubule before reaching loop of Henle

71
Q

What is the primary tool to reabsorb sodium, chloride, and water?

A

Sodium-potassium ATPase pump

72
Q

What substances are rapidly reabsorbed in the first half of the proximal tubule?

A

Sodium, glucose, amino acids, and water

73
Q

A high concentration of which ions are left in the second half of the proximal tubule?

A

Chloride

74
Q

What is the proximal tubule highly permeable to?

A

Water (providing constant osmolarity)

Physiology III Final Exam (6 decks)

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