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human physiology and exercise > renal sodium and water regulation > Flashcards

renal sodium and water regulation Flashcards

1
Q

describe fluid compartments of the body

A
  • water makes up 60% of males lean body weights
  • water makes up 55% of females weight
  • 2/3 intracellular; 1/3 extracellular
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2
Q

describe fluid percentage of plasma and interstitial fluid

A
  • 7%= plasma fluid
  • 28 % = interstitial fluid
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3
Q

describe factors causing water gain and water loss

A

-water gain= liquids, food ingestion, metabolically produced
- water loss= insensible loss (evaporation from skin/ lungs) ,sweat, faeces and urine

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4
Q

describe factors causing sodium chloride gain and loss

A
  • gain= food
  • loss= sweat, faeces, gastrointestinal tract, urine
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5
Q

how is sodium regulated?

A
  • sodium actively reabsorbed in all tubules expect descending LOH and collecting duct
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6
Q

how is water regulated? what is it dependent on?

A
  • occurs through diffusion
  • dependent on Na levels
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7
Q

how does water move ?

A
  • through aquaporin channel’s
  • none in collecting duct
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8
Q

where does water change detection occur?

A
  • in neurons in hypothalamus
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9
Q

describe what happens when high plasma osmolarity is detected

A
  • sensation of thirst and ADH release
  • fluid intake and increased water reabsorption
  • water is gained
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10
Q

describe what happens when low plasma osmolarity is detected

A
  • thirst and ADH release decrease
  • decrease in water reabsorption
  • water lost
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11
Q

what is ECF volume?

A
  • extracellular fluid
  • amount of fluid that is outside of the cells in the body
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12
Q

when does ECF volume decrease?

A
  • reabsorb more sodium, thirst and ADH retains water
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13
Q

when does ECF volume increase?

A
  • reabsorb less sodium and water reabsorption decreases
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14
Q

how is changes in sodium content signalled? what is sodium balance linked to?

A
  • signalled by changes in ECF volume that perfuses our tissues
  • linked to blood pressure and volume
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15
Q

describe sodium reabsorption

A
  • active process achieved by Na+/ K+- ATPase pump (keeps Na levels low to allow downhill movement from lumen)
  • mechanisms of Na+ movement across luminal membrane varies between tubules
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16
Q

when is Na+/k+ always used?

A
  • for basolateral membrane
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17
Q

describe different transport in proximal tubule and cortical collecting duct

A
  • PT= co- transport of organic molecules e.g. glucose, amino acids
  • cortical CD= Na+ channels
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18
Q

describe the coupling of water reabsorption and sodium reabsorption

A
  • Na reabsorption creates an osmotic difference> drives water reabsorption
  • H20 moves through epithelial cells and into interstitial fluid
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19
Q

what does anti- diuretic hormone indicate?

A

-cascade of events within the cells that leads to an increased number of AQP2 channels in luminal membrane
- allows increased passive diffusion of H20 into cells

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20
Q

where does water exit? what are these not sensitive to compared to ADH?

A
  • exits through AQP3
  • not sensitive to vasopressin
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21
Q

describe aquaporins

A
  • water channels that are activated and moved towards the cell wall to transport water out tubules+ back into body
  • operate in collecting ducts
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22
Q

what stimulates the aquaporin channels?

A
  • anti - diuretic hormone (vasopressin) stimulates them
23
Q

what system does ADH use and what for?

A
  • cAMP systems to cause insertion of aquaporins into membranes of cells of collecting duct
24
Q

what does insertion of aquaporins in membrane of cells in CD cause?

A
  • outflow of water out of collecting ducts to be reabsorbed
25
Q

where does regulation of ADH release occur?

A
  • posterior pituitary gland
  • receives signals from baroreceptors and osmoreceptors
26
Q

why is absorption control more important than GFR?

A
  • more important for long term regulation of Na+ excretion
27
Q

what 3 factors determine the rate of tubular Na+ reabsorption?

A
  • aldosterone
  • atrial natriuretic peptide
  • local effect of bp on tubules
28
Q

how does aldosterone and renin- angiotensin system start?

A
  • release of renin converts peptide angiotensinogen to angiotensin 1
29
Q

what happens to the angiotensin 1?

A
  • converted to angiotensin II by angiotensin converting enzyme
  • enzyme acts on adrenal glands, kidneys and brains (target cells)
30
Q

what happens due to angiotensin converting enzyme?

A
  • activation of receptors in adrenal gland stimulates aldosterone release
  • increases Na+ and H20 reabsorption
  • decrease in plasma volume ^ Na+ reabsorption
31
Q

what is ANP and where is it synthesised and released?

A
  • atrial natriuretic peptide
  • synthesised in heart
  • released by atrial myocytes
32
Q

when is ANP released and what does an increase in ANP circulation cause?

A
  • released in response to atria stretching when circulatory blood volume increases
  • it works to increase Na+ excretion
33
Q

what does regulation of bodily fluid osmolarity require?

A
  • separation of water excretion from Na+ excretion
  • allowed via osmoreceptors and ADH dependent water reabsorption without Na+ reabsorption into CDs
34
Q

what role does renal system play in regulating bp?

A
  • sodium and water key in regulating bp
35
Q

describe local effects of blood pressure on tubules

A
  • baroreceptors regulate blood pressure simultaneously regulating total body sodium
36
Q

what is GFR affected by?

A
  • volume of surface available
  • filtration membrane permeability
  • NFP (net filtration pressure)
  • blood flow to glomerular capillaries
37
Q

what is GFR directly proportion to? what does this mean?

A
  • proportional to NFP
  • increase in systemic blood pressure increases GFR
38
Q

describe inputs controlling thirst- how are deficits compensated ?

A
  • kidneys cannot create new Na+ or H20 so deficits must eventually be compensated by ingestion
39
Q

what are diuretics? state an example

A
  • promotes loss of Na+ H20
  • can be used to control BP
  • alcohol inhibits the release of vasopressin
40
Q

what are osmotic diuretic

A
  • carbs that are filtered but not reabsorbed
41
Q

what are loop diuretics?

A
  • most powerful as they inhibit the formation of medullar gradient through inhibiting Na+ reabsorption
42
Q

what are hydrochlorothiazide diuretics?

A
  • acts on distal collecting duct
43
Q

what are spironolactone diuretics?

A
  • example of an aldosterone receptor antagonist
  • K+ in urine is from aldosterone- driven active tubular secretion into DCT and collecting duct
44
Q

what happens to renal blood as exercise intensity increases?

A
  • as exercise intensity increases renal blood flow decreases
45
Q

when is GFR only affected?

A
  • at exercise intensities above 50% of V02 max
46
Q

what system is used during exercise and what does this cause?

A
  • sympathetic to vasoconstrict renal arterioles and hence reduce blood flow
47
Q

what else reduces renal blood flow during exercise?

A
  • increase ADH release due to renin- angiotensin- aldosterone system
48
Q

what do kidneys do during exercise?

A
  • kidneys have higher workload to buffer hydrogen ions
  • remove 2% lactate produced
49
Q

how do kidneys maintain pH during exercise?

A
  • loss of excess H+ in urine
  • lactate removed
50
Q

how do kidneys conserve water?

A
  • through anti- diuretic hormone and Na+ reabsorption
  • fluid regulatory hormones
51
Q

what do kidneys excrete post exercise?

A
  • excrete metabolites e.g. creatine for muscle breakdown
52
Q

what is rhabdomyolysis?

A
  • condition where skeletal muscle cell damage can cause acute renal failure and sometimes death
53
Q

what increases the risk of rhabdomyolysis ?

A
  • heat stress and dehydration

human physiology and exercise (18 decks)

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