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Food + Physiology > Water balance > Flashcards

Water balance Flashcards

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1
Q

what does the kidney maintain within the body

A

maintains:

  • water balance in body
  • plasma volume (blood pressure)
  • acid-base balance (pH)
  • osmolarity (solute concentration)
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2
Q

what waste products does the kidney regulate

A

urea
uric acid
creatinine

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3
Q

what does the kidney regulate within the body

A

extracellular fluid ion concentration

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4
Q

what does the kidney excrete

A

excretion of:

  • waste products of body metabolism
  • foreign compounds
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5
Q

what foreign compounds may the kidney excrete

A

food additives
drugs
pesticides

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6
Q

what does the kidney secrete and what are the secretions used for

A

erythropoietin (red blood cell production)

renin (hormone regulation salt conservation)

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7
Q

how does the kidney link to vitamin D

A

converts it to an active form

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8
Q

what is the main excretory product produced by the kidney

what is it produced by

A

urine

  • filtration of plasma
  • reabsorption from filtrate
  • secretion directly into filtrate
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9
Q

how many nephrons are there per kidney

A

1 million

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10
Q

what makes up the vascular component of the kidney and what is its function

A

glomerulus - ball of capillaries

water and solutes filtered out here from the blood

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11
Q

what is the function of the tubular component of the kidney

A

fluid passes into tubular after vascular

fluid is modified

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12
Q

what makes up the afferent arterioles

A

large amount of small vessels

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13
Q

how many arterioles supply a nephron

A

one

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14
Q

what does the afferent arteriole do

A

deliver blood to glomerular capillaries

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15
Q

what makes up the efferent arterioles

A

formed by re-joining glomerular capillaries

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16
Q

what are the efferent arterioles divided into

A

peritubular capillaries

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17
Q

where does the efferent arteriole provide blood to

A

carry blood that was not filtered into tubules

supply renal tissue with blood

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18
Q

what is the tube in the tubular component made up of

A

hollow tube formed from single layer epithelial cells

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19
Q

what does the tubular component consist of

A 
hollow tube
bowmans capsule
proximal tubule in cortex
loop of henle 
distal tubule
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20
Q

what is the bowmans capsule

A

cups around the glomerulus to collect fluid

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21
Q

what is the function of the loop of henle

A

establishes an osmotic gradient essential for concentrating urine

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22
Q

what is the distal tubule

A

highly coiled

lies in cortex and empties into collecting duct

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23
Q

is the glomerular membrane permeable

A

100x more permeable than other capillaries

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24
Q

what does glomerular filtration depend on

A

hydrostatic pressure

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25
Q

how does colloid osmotic pressure form

A

in plasma contains proteins, if these are not passed into the filtrate - their concentrated in the unfiltered plasma increases = exert resistance to further filtration of fluid

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26
Q

what is GFR

A

glomerular filtration rate

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27
Q

how is GFR reduced

A

afferent arteriole - vasoconstriction decreases blood flow into glomerulus

  • decrease glomerular capillary blood pressure
  • decrease net filtration pressure
  • decrease GFR
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28
Q

how is GFR increased

A

afferent arteriole - vasodilation increases blood flow into glomerulus

  • increases glomerular capillary blood pressure
  • increases net filtration pressure
  • increases GFR
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29
Q

what prevents fluctuations in GFR

A

auto regulation of arteriole diameters

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30
Q

what type of mechanism is auto regulation

A

myogenic mechanism - afferent arteriole contracts in response to stretching from increased blood flow

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31
Q

what happens if the afferent arteriole contracts

A

decrease blood flow into glomerulus

32
Q

what is the feedback mechanism involved in auto regulation

A

tubuloglomerular feedback mechanism - local vasoconstrictor/vasodilator release

33
Q

what is a neural mechanism

A

extrinsic control from sympathetic nervous system

34
Q

what are the characteristics of tubular reabsorption

A

occurs at very high rate
highly selective
highly variable

35
Q

how does a diabetics urine differ

A

higher glucose concentration as they have higher glucose concentration in blood, kidneys cannot reabsorb all of it

36
Q

what must a substance do to be reabsorbed

A
  • cross luminal membrane of tubular cell
  • pass through tubular cell cytosol
  • cross tubular cell basolateral membrane to enter interstitial fluid
  • diffuse through interstitial fluid
  • penetrate capillary wall to enter blood plasma
37
Q

what does the extracellular fluid osmolarity depend on

A

relative amount of water to solute

38
Q

what makes up 2/3rds of bodys water

A

intra cellular fluid (within cells)

39
Q

what makes up the extracellular fluid

A 
plasma 
interstitial fluid (spaces between cells)
40
Q

if the water balance is normal what is the ECF

A

isotonic

41
Q

if the water balance is too much water what is the ECF

A

hypotonic

42
Q

if the water balance is too little water what is the ECF

A

hypertonic

43
Q

what are the concentrations that urine can be excreted between

A

100-1200 mosm/l

44
Q

what is the vertical osmotic gradient

A

in the renal medulla
intracellular fluid all of the cortex is ~ 300 mosm/l
descend into medulla intracellular fluid more concentrated ~ 1200 mosm/l

45
Q

what causes the medulla intracellular fluid concentration to be so high

A

sodium and chloride ions ~ 300 mosm each

urea contribute to rest concentration

46
Q

what is the counter current multiplication

A

as fluid flows down water diffuses out down osmotic gradient so concentration increases
fluid flows back salt is actively pumped out so concentration decreases

47
Q

where does the counter current multiplication occur

A

loop of henle

48
Q

how is the proximal convoluted tubule specialised

A

luminal border microvilli increase surface area

49
Q

what occurs in the descending limb

A

ONLY permeable to water

water diffuses out of descending limb down conc gradient

50
Q

what occurs in the thin ascending limb

A

not permeable to water
high permeability to sodium and chloride ions
NaCl diffuse out limb down conc gradient

51
Q

what occurs in the thick ascending limb

A

ACTIVELY pumps out sodium and chloride

does do efficiently only concentrated by urea

52
Q

what does the distal convoluted tubule transport into the lumen

A

transport into lumen:

  • potassium ions
  • hydrogen protons
  • ammonia
53
Q

what does the distal convoluted tubule transport out of the lumen

A
  • sodium ions
  • chloride ions
  • bicarbonate ions

as salt pumped out water follows

54
Q

what happens at the collecting duct

A

permeable to water
water flow from dilute urine to more concentrated interstitial fluid of renal medulla - back to ~300 msom as reach CD
reabsorbs NaCl by active transport
high permeability to urea at bottom

55
Q

when are the distal and collecting tubules not permeable to water

A

when vasopressin (anti-diuretic hormone) not present

56
Q

where is the vasopressin made

A

hypothalamus

57
Q

where is the vasopressin stored

A

posterior pituitary gland

58
Q

when is the release of vasopressin stimulated

A

water deficit

59
Q

what happens for water channels to be inserted in DCT and CD

A

vasopressin binds to the receptor on the DCT basolateral membrane
once activated, receptor cyclises ATP to cyclic AMP - causes water channels to be inserted

60
Q

what triggers release of vasopressin and thirst

where are they located

A

hypothalamic osmoreceptors

- neat vasopressin secreting cells and thirst centre

61
Q

what happens when increased osmolarity in surrounding fluid

A

vasopressin release

thirst triggered

62
Q

what happens when decreased osmolarity in surrounding fluid

A

inhibition of vasopressin release

suppression of thirst

63
Q

what else regulates vasopressin

A

volume receptors

- monitor blood pressure

64
Q

which fluid can be directly acted on to regulate volume and composition

A

plasma

65
Q

how id fluid balance regulated

A

through ECF volume and osmolarity

66
Q

what regulates the ECF osmolarity

A

maintenance of water balance

67
Q

what regulates the ECF volume

A

maintenance of salt balance

68
Q

what uses most of the kidneys energy

A

sodium reabsorption 80%

69
Q

how much of the filtered sodium is reabsorbed

and where

A

99.5%
67% PCT
25% loop of henle
8% DCT

70
Q

how is sodium concentration reflected in ECF volume

A

high sodium load = extra water in ECF and volume increases

low sodium load = less water held in ECF and volume decreases

71
Q

what does the ECF volume effect

A

blood pressure

72
Q

what is angiotensinogen

A

precursor constantly secreted into circulatory system

73
Q

what happens in the renin-angiotensisn-aldosterone system when e.g. atrial blood pressure drops/ ECF drops/ decrease in NaCl

A

kidney detects change and releases renin
renin cleaves apart angiotensinogen = angiotensin I
pass through lungs where angiotensin-converting enzyme cleaves more of angiotensin I = angiotensin II (active hormone)
angiotensin II pass to adrenal cortex = release of aldosterone
aldosterone causes increase in sodium reabsorption in kidney tubule
angiotensin II then helps correct

74
Q

what does angiotensin II do to help correct in the renin-angiotensisn-aldosterone system

A

angiotensin II causes:

  • facilitated release of vasopressin - retain fluid
  • thirst to drink more
  • as blood pressure lower - need to maintain certain pressure, causes arteriolar vasoconstriction
75
Q

what does aldosterone do

A

increases sodium reabsorption in DCT and CD

  • insert additional sodium ion channels into luminal membranes
  • insert additional sodium potassium ATPase carrier into basolateral membranes
76
Q

if no aldosterone is present how much salt is secreted

A

up to 20g a day

77
Q

if aldosterone is present how much salt is secreted

A

non

Food + Physiology (17 decks)

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