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Physiology Exam 3 > Lecture 18: Tubular Reabsorption and Secretion > Flashcards

Lecture 18: Tubular Reabsorption and Secretion Flashcards

1
Q

For a substance to be reabsorbed it must be transported to where?

A

across the tubular epithelial membranes into the renal interstitial fluid
through the particular capillary membrane back into the blood

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2
Q

What channels is water transported through?

A

aquaporins

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3
Q

Where is aquaporin 1 located?

A

widespread, including renal tubules

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4
Q

Where is aquaporin 2 located?

A

present in apical membranes of collating tubule cells

controlled by ADH

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5
Q

Where is aquaporin 3 located?

A

present in basolateral membranes of collecting tubule cells

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6
Q

_______ establish ionic gradients across nephron cell membranes

A

ATPases

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7
Q

Describe ENaC channels

A

found in apical membrane of nephron cells
closed by drug amiloride
opened by number of hormones

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8
Q

Where are CTFR and K+ channels found?

A

apical membranes of some segments of nephron

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9
Q

What are some primary active transporters?

A

Na+ K+ ATPase
H+ATPase
H+K+ATPase
Calcium ATPase

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10
Q

Reabsorption of glucose or amino acids by renal tubule are example of ________ transport

A

secondary active

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11
Q

What substances are actively secreted into the renal tubules?

A

creatinine

para aminohippuric acid

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12
Q

What is the transport maximum?

A

limit to the rate at which the solute can be transported due to saturation of a specific transport system

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13
Q

Transport max for glucose=

A

375 mg/min

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14
Q

filtered load for glucose =

A

125 mg/min

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15
Q

GFR x plasma glucose =

A

125 ml/min x 1 mg/ml

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16
Q

What are some reasons why some passively reabsorbed substances do not have a transport maximum?

A

rate of diffusion is determined by electrochemical gradient of substance
permeability of the membrane for the substance
time that the fluid contacting the substance remains within the tubule

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17
Q

What does the rate of transport depend on?

A

electrochemical gradient

time the substance is in the tubule

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18
Q

What is passive water reabsorption coupled to?

A

sodium reabsorption

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19
Q

Describe the proximal tubule

A
  • highly metabolic with large numbers of mitochondria
  • extensive brush border on luminal surfaces
  • extensive intercellular and basal channels on interstitial surfaces
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20
Q

What does the proximal tubule reabsorb?

A

65% of filtered sodium, chloride, bicarbonate, potassium

all filtered glucose and amino acids

21
Q

What does the proximal tubule secrete?

A

organic acids, bases, and hydrogen ions into tubular lumen

22
Q

In the first half of the proximal tubule, sodium reabsorption is via co transport with ______ ____ and _____

A

glucose, sodium, and other solutes

23
Q

In the second half of the proximal tubule, reabsorption is mostly with _____

A

chloride ions

24
Q

The thin descending segment of the loop of Henle is _____ permeable to water and _____ permeable to most solutes, including urea and sodium

A

highly; moderately

25
Q

the thin descending segment of the loop of Henle reabsorbs about _____ percent of filtered water

A

20

26
Q

The thin ascending loop of Henle is ______ to water

A

impermeable

27
Q

Thick ascending loop of Henle is ______ to water

A

impermeable

28
Q

The first portion of the distal tubule forms the ______

A

macula densa

29
Q

Is the distal tubule permeable to water and urea?

A

no

30
Q

Describe principal cells

A

reabsorb Na+ and water from tubular lumen
secrete K+ into tubular lumen
uses Na+K+ATPase pump
primary site of K+ sparing diuretics

31
Q

Describe intercalated cells

A

reabsorb K+ from tubular lumen

secrete H+ into tubular lumen

32
Q

Is the medullary collecting duct permeable to water and urea? what is controlled by?

A

yes; ADH

33
Q

What is the source of aldosterone?

A

adrenal cortex

34
Q

What is the function of aldosterone?

A

increases sodium reabsorption and stimulates potassium secretion

35
Q

What is the site of action for aldosterone?

A

major site of action is on the principal cells of cordial collecting ducts

36
Q

What is the stimulus for secretion for aldosterone?

A

increased extracellular potassium

increased levels of angiotensin II

37
Q

What happens if there is an absence of aldosterone?

A

Addison’s disease

marked loss of sodium and accumulation of potassium

38
Q

What happens in there is a hyper secretion of aldosterone?

A

Conn’s syndrome

39
Q

What is the function of Angiotensin II?

A

increased sodium and water reabsorption

returns blood pressure and extracellular volume toward normal

40
Q

What are the effects of angiotensin II?

A

stimulates aldosterone secretion
constricts efferent arterioles
directly stimulates sodium reabsorption in proximal tubules, loops of Henle, distal tubules, and collecting ducts

41
Q

What is the source of ADH?

A

posterior pituitary

42
Q

What is the function of ADH?

A

increases water reabsorption

43
Q

What are the effects of ADH?

A

binds to V2 receptors in late distal tubules, collecting tubules, and collecting ducts
increases formation of cAMP

44
Q

What is the source of atrial natriuretic peptide?

A

cardiac atrial cells in response to distention

45
Q

What is the function of atrial natriuretic peptide?

A

inhibits reabsorption of sodium and water

46
Q

What is the source of parathyroid hormone?

A

parathyroid glands

47
Q

What is the function of parathyroid hormone?

A

increases calcium reabsorption

48
Q

What is the renal clearance of a substance equal to?

A

volume of plasma that is completely cleared of the substance by the kidneys per unit time

Physiology Exam 3 (9 decks)

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