Exam - The Tubular Function

Question 1

what are events occurring in the tubules

Answer 1

glomerular filtration

Question 2

what occurs in glomerular filtration

Answer 2

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

Question 3

what happens to the fluid in the tubule

Answer 3

it gets transformed into urine

Question 4

reabsorption of fluid

Answer 4

water and dissolved substance from tubular lumen to peritubular capillaries

Question 5

secretion of fluid

Answer 5

substances transported from the peritubular capillaries to the tubular lumen

Question 6

in passive reabsorption, what determines what is passively absorbed

Answer 6

molecular size and liposolubility

Question 7

how much urea is passively reabsorbed

Answer 7

50-60%

Question 8

examples of substances in passive reabsorption

Answer 8

negative ions
drugs
environmental toxins

Question 9

what is tubular secretion for

Answer 9

only selected substances

Question 10

where does tubular secretion occur

Answer 10

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

Question 11

how does tubular secretion occur

Answer 11

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

Question 12

what would be secreted by primary active transport

Answer 12

one system for organic acids
one system for organic bases

Question 13

what would be secreted by secondary active transport

Answer 13

H+

Question 14

what would be secreted by passive diffusion

Answer 14

several steroid hormones
drugs

Question 15

what does glucose filter as easily as

Answer 15

water –>glucose concentration in glomerular filtrate = plasma concentration

Question 16

where is glucose reabsorbed

Answer 16

only in proximal tubule

Question 17

how does glucose get reabsorbed

Answer 17

secondary active transport

Question 18

do kidneys participate in regulating glucose levelds

Answer 18

no, just prevent its loss

Question 19

will glucose appear in urine

Answer 19

not normally unless glucose concentration in plasma is extreme

Question 20

renal threshold for glucose

Answer 20

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

Question 21

splay

Answer 21

deviation from an ideal curve

Question 22

what happens if there is glucose in urine

Answer 22

diabetes mellitus

Question 23

what are the the first main causes of diabetes mellitus

Answer 23

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

Question 24

what is the second main cause of diabetes mellitus

Answer 24

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

Question 25

do proteins pass through the glomerular membrane

Answer 25

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

Question 26

what are proteins reabsorbed by

Answer 26

epithelial cells of the proximal tubules by endocytosis

Question 27

what happens to proteins once reabsorbed

Answer 27

they are broken down into amino acids in epithelial cells

Question 28

where can residual amounts of proteins in urine be sometimes observed

Answer 28

in dogs

Question 29

is it normal for there to be proteins in the urin

Answer 29

no - glomerulus should not let them pass

Question 30

what is the main reason for protein leakage

Answer 30

imbalance of charge in glomerular membrane

Question 31

why are proteins repulsed by basal lamina

Answer 31

proteins are negatively charged and so is the basal lamina

Question 32

when can some proteins pass through the membrane

Answer 32

if the membrane loses its polarit

Question 33

why is there a low ion concentration in urine

Answer 33

the reabsorption of many ions equals the amount filtered

Question 34

how are ions regulated

Answer 34

most of the reabsorption of ions is hormonally controlled

Question 35

what affects plasma levels and thus filtration for most ions

Answer 35

intestinal absorpotion

Question 36

what is the most important organ for Na+ control

Answer 36

kidney

Question 37

what is the most important factor regulating extracellular and blood volumes

Answer 37

Na+

Question 38

what is the additional importance of Na+

Answer 38

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

Question 39

examples of things that are transported coupled to Na+

Answer 39

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

Question 40

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

Answer 40

80%

Question 41

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

Answer 41

proximal tubule

Question 42

characteristic of proximal tubule

Answer 42

porous

Question 43

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

Answer 43

less

Question 44

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

Answer 44

barely - tight junctions between epithelial cells

Question 45

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

Answer 45

hormonal control

Question 46

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

Answer 46

aldosterone

Question 47

what is a mineralocorticoid

Answer 47

liposuble steroid hormone synthesized and released by the adrenal cortex

Question 48

what does aldosterone induce

Answer 48

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

Question 49

what happens if there is no aldosterone

Answer 49

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

Question 50

were is ECF content relatively low

Answer 50

inside cells - needs to be maintained within a narrow Rangel

Question 51

where is K+ reabsorbed

Answer 51

actively in proximal tubule

Question 52

where is K+ secreted

Answer 52

distal tubule and collecting duct

Question 53

what are changes in K+ mainly due to

Answer 53

secretion since 100% filtered is reabsorbed

Question 54

what does K+ concentration control

Answer 54

aldosterone release

Question 55

what percentage of Ca2+ is bound to proteins in plasma

Answer 55

50%

Question 56

what form of Ca2+ can be filtered in glomerulus

Answer 56

only free form

Question 57

where is Ca2+ reabsorbed

Answer 57

mostly in proximal tubule

Question 58

where does the regulated reabsorption of Ca2+ occur

Answer 58

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

Question 59

what stimulates Ca2+ reabsorption

Answer 59

parathyroid hormone (PTH)

Question 60

what percentage of filtered Ca2+ is generally excreted

Answer 60

1-2%

Question 61

what is very important to maintain blood volume

Answer 61

tubular reabsor[tion of water

Question 62

how does tubular reabsorption of water occur

Answer 62

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

Question 63

what is the tubular reabsorption of water influenced by

Answer 63

movements of Na+ because osmosis is a diffusion process

Question 64

where does most water reabsorption occur

Answer 64

proximal tubular

Question 65

what do most structures possess

Answer 65

aquaporins

Question 66

what structure does not posses aquaporins

Answer 66

the ascending limb of the loop of Henle

Question 67

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

Answer 67

ADH from pituitary --> increases water reabsorption