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ANSC 3080 > Exam - The Tubular Function > Flashcards

Exam - The Tubular Function Flashcards

1
Q

what are events occurring in the tubules

A

glomerular filtration

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2
Q

what occurs in glomerular filtration

A

bulk movements (water + dissolved substances) –> tubular fluid composition close to a protein free plasma

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3
Q

what happens to the fluid in the tubule

A

it gets transformed into urine

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4
Q

reabsorption of fluid

A

water and dissolved substance from tubular lumen to peritubular capillaries

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5
Q

secretion of fluid

A

substances transported from the peritubular capillaries to the tubular lumen

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6
Q

in passive reabsorption, what determines what is passively absorbed

A

molecular size and liposolubility

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7
Q

how much urea is passively reabsorbed

A

50-60%

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8
Q

examples of substances in passive reabsorption

A

negative ions
drugs
environmental toxins

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9
Q

what is tubular secretion for

A

only selected substances

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10
Q

where does tubular secretion occur

A

from peritubular capillaries –> across tubular cells –> into lumen

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11
Q

how does tubular secretion occur

A

some by primary active transport, some by secondary active transport, some by passive diffusion

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12
Q

what would be secreted by primary active transport

A

one system for organic acids
one system for organic bases

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13
Q

what would be secreted by secondary active transport

A

H+

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14
Q

what would be secreted by passive diffusion

A

several steroid hormones
drugs

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15
Q

what does glucose filter as easily as

A

water –>glucose concentration in glomerular filtrate = plasma concentration

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16
Q

where is glucose reabsorbed

A

only in proximal tubule

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17
Q

how does glucose get reabsorbed

A

secondary active transport

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18
Q

do kidneys participate in regulating glucose levelds

A

no, just prevent its loss

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19
Q

will glucose appear in urine

A

not normally unless glucose concentration in plasma is extreme

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20
Q

renal threshold for glucose

A

the lowest plasma concentration at which glucose can be detected in urine

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21
Q

splay

A

deviation from an ideal curve

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22
Q

what happens if there is glucose in urine

A

diabetes mellitus

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23
Q

what are the the first main causes of diabetes mellitus

A

insulin regulation of blood glucose does not work –>glucose levels in plasma increase dramatically passed the Tmax —> kidney cannot handle it all –> excretes glucose

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24
Q

what is the second main cause of diabetes mellitus

A

genetic defect affecting the transport mechanism of glucose in the proximal tubule –> reduced Tmax –> glucose excreted even when plasma levels are low

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25
Q

do proteins pass through the glomerular membrane

A

no - not usually present in glomerular filtrate except small peptides and small proteins

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26
Q

what are proteins reabsorbed by

A

epithelial cells of the proximal tubules by endocytosis

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27
Q

what happens to proteins once reabsorbed

A

they are broken down into amino acids in epithelial cells

28
Q

where can residual amounts of proteins in urine be sometimes observed

A

in dogs

29
Q

is it normal for there to be proteins in the urin

A

no - glomerulus should not let them pass

30
Q

what is the main reason for protein leakage

A

imbalance of charge in glomerular membrane

31
Q

why are proteins repulsed by basal lamina

A

proteins are negatively charged and so is the basal lamina

32
Q

when can some proteins pass through the membrane

A

if the membrane loses its polarit

33
Q

why is there a low ion concentration in urine

A

the reabsorption of many ions equals the amount filtered

34
Q

how are ions regulated

A

most of the reabsorption of ions is hormonally controlled

35
Q

what affects plasma levels and thus filtration for most ions

A

intestinal absorpotion

36
Q

what is the most important organ for Na+ control

A

kidney

37
Q

what is the most important factor regulating extracellular and blood volumes

A

Na+

38
Q

what is the additional importance of Na+

A

transport of other substances are coupled to Na+ in secondary active transport

39
Q

examples of things that are transported coupled to Na+

A

the reabsorption of glucose, amino acid, bicarbonate, Cl-, and PO4-
secretion of H+ and K+

40
Q

how much of the metabolism of the kidney is energy spent in Na+ transport

A

80%

41
Q

where is th site of most Na+ and filtered water reabsorption

A

proximal tubule

42
Q

characteristic of proximal tubule

A

porous

43
Q

is the loop of Henle less of more permeable than the proximal tubule

A

less

44
Q

are the distal tube and collecting duct permeable to Na+ and water

A

barely - tight junctions between epithelial cells

45
Q

what is permeability and reabsorption in the last part of the distal tubule and collecting duct controlled by

A

hormonal control

46
Q

what is the most important factor stimulating Na+ reabsorption int he distal tubule and collecting duct

A

aldosterone

47
Q

what is a mineralocorticoid

A

liposuble steroid hormone synthesized and released by the adrenal cortex

48
Q

what does aldosterone induce

A

synthesis of Na+ channels and pump in epihtlial cells, therefore increasing Na+ transport

49
Q

what happens if there is no aldosterone

A

all the Na+ entering the distal tubule will be excreted in urine = death within a couple of days

50
Q

were is ECF content relatively low

A

inside cells - needs to be maintained within a narrow Rangel

51
Q

where is K+ reabsorbed

A

actively in proximal tubule

52
Q

where is K+ secreted

A

distal tubule and collecting duct

53
Q

what are changes in K+ mainly due to

A

secretion since 100% filtered is reabsorbed

54
Q

what does K+ concentration control

A

aldosterone release

55
Q

what percentage of Ca2+ is bound to proteins in plasma

A

50%

56
Q

what form of Ca2+ can be filtered in glomerulus

A

only free form

57
Q

where is Ca2+ reabsorbed

A

mostly in proximal tubule

58
Q

where does the regulated reabsorption of Ca2+ occur

A

in the ascending limb of the loop of Henle, the distal tubule and the collecting ducts

59
Q

what stimulates Ca2+ reabsorption

A

parathyroid hormone (PTH)

60
Q

what percentage of filtered Ca2+ is generally excreted

A

1-2%

61
Q

what is very important to maintain blood volume

A

tubular reabsor[tion of water

62
Q

how does tubular reabsorption of water occur

A

between epithelial cells through a tight junction
through epithelial cells (aquaporins)

63
Q

what is the tubular reabsorption of water influenced by

A

movements of Na+ because osmosis is a diffusion process

64
Q

where does most water reabsorption occur

A

proximal tubular

65
Q

what do most structures possess

A

aquaporins

66
Q

what structure does not posses aquaporins

A

the ascending limb of the loop of Henle

67
Q

what are aquaporins up regulated by in the distal tubule and collecting duct

A

ADH from pituitary –> increases water reabsorption

ANSC 3080 (41 decks)

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