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HUBS192 > Lecture 33 physio Body water - distribution and regulation > Flashcards

Lecture 33 physio Body water - distribution and regulation Flashcards

1
Q

whats the general functions of the kidneys?

A

Water homeostasis (hydration, blood pressure)
Salt/ion homeostasis (Na+, K+, Ca2+ blood pressure)
Re-absorption of nutrients (amino acids, glucose)

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2
Q

What drives and regulates body water homeostasis?

A
  • distribution of body water
  • osmolarity/tonicity of solutions
  • reabsorption of water in the nephron
  • changes in body osmolarity
  • effects of osmotic changes in the kidney
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3
Q

whats the distribution of body water?

A 
TBW (55%-60%)
ICF (2/3 of TBF)
ECF (1/3 of TBW)
Plasma (1/5 of ECF)
ISF
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4
Q

whats the distribution of body water compared amongst males and females?

  • TBF
  • ICF
  • ECF
  • ISF
  • Plasma
A

males have more than females

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5
Q

whats the distribution of body water in males?

  • TBF
  • ICF
  • ECF
  • ISF
  • Plasma
A 
42L (60%)
28L
14L
11.2L
2.8L
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6
Q

whats the distribution of body water in females?

  • TBF
  • ICF
  • ECF
  • ISF
  • Plasma
A
  1. 5L (55%)
  2. 8L
  3. 7L
  4. 2L
  5. 5L
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7
Q

whats osmolarity based on?

A

number of osmotically active ions or solutes

145 mM NaCl =
145 mM Na+ + 145 mM Cl- = 290 mosmol/L

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8
Q

what can osmolarity be estimated by?

A

specific gravity (density of solutions)

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9
Q

whats osmolarity units?

A

mosmol/L

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10
Q

what are the terms given in osmolarity?

A

Iso - same osmolarity
Hypo - low osmolarity
Hyperosmotic - higher osmolarity solutions

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11
Q

Whats tonicity based on?

A

the effect of a solution on cells

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12
Q

what does an isotonic solution not do?

A

does NOT change water homeostasis between cells

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13
Q

whats the osmolarity in the ECF (plasma) and ICF (muscle)?

A

275-295 mosmol/L

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14
Q

body water – whats the composition of ECF (plasma) and ICF (muscle)?

Na+
K+
Ca2+
Cl-
HCO3-
pH
osmolarity
A

ECF

  • 145
  • 4-5
  • 2
  • 110
  • 24
  • 7.4
  • 275-295 mosmol/L

ICF

  • 15
  • 150
  • 10^-4
  • 5
  • 10
  • 7.1
  • 275-295 mosmol/L
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15
Q

total body water remains relatively constant.

what must the intake and loss of water be? and what is adjusted to maintain balance?

A

balance

urine output is adjusted to maintain balance (1400mL)

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16
Q

what are the 4 important places within the nephron, where sodium is reabsorbed?

A

PCT (67%),
TAL (25%),
DCT (5%),
CCT (3%)

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17
Q

what are the three important places within the nephron, where water is reabsorbed?

A

PCT (67%),
tDLH (25%),
CCT (2 - 8%)

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18
Q

water re-absorption in the proximal tubule (67% of the filtered load). what is it driven by?

A

Na+ reabsorption (isosmotic!!)

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19
Q

what is water re-absorption facilitated by?

A

aquaporins (trans-cellular) and via leaky tight junctions (paracellular)

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20
Q

what transporters use the Na+ gradient and why?

A

transporters - sodium glucose-cotransporter use the sodium gradient to reabsorb glucose

21
Q

what does the TAL do?

A

reabsorbs Na+ into the interstitium

22
Q

whats the tDL?

A

leaky epithelium facilitating water reabsorption via aquaporins (transcellular) and the paracellular pathway

23
Q

Water

A. in the body is mostly stored in the ECF.
B. permeability of the TAL is high.
C. concentration of the urine is high under anti-diuretic conditions.
D. re-absorption in the Loop of Henle is to the same extent as sodium re-absorption.
E. balance in the body is mostly controlled by the lungs.

A

D. re-absorption in the Loop of Henle is to the same extent as sodium re-absorption.

24
Q

what does changing water content change?

A

osmolarity anf cell size

fluid shifts between ECF - ICF to equalise

volume of compartments change

25
Q

what environment do RBC depend on? what changes the function?

A

isotonic environment

hypertonic or hypotonic environments

26
Q

do ICF/ECF have same osmolarity 275-295 mosmol/L?

A

yes

27
Q

where does water move?

A

between ICF and ECF

moves to areas of high osmolarity until osmolarity equalised

28
Q

what happens to the compartment that water moves into?

A

INCREASE in volume

regulate water to regulate osmolarity to regulate cell size

29
Q

changes in body osmolarity - dehydration

what happens to ECF if dont drink water?

A

water lost (only) from ECF

ECF osmolarity increases to ~ 320 mosmol/L (ECF gets more concentrated)

difference between: ECF: 320mosmol/L vs ICF 285mosmol/L

water moves to higher osmolarity

from ICF (cells) to ECF until osmolarity balanced

BUT cells will become SMALLER

ECF osmolarity has to be controlled!!

30
Q

where does water move to during dehydration not drinking? what will happen to the cells?

A

moves to higher osmolarity

from ICF (cells) to ECF until osmolarity balanced

cells will become SMALLER

ECF osmolarity has to be controlled!!

31
Q

changes in body osmolarity - hyperhydration

what happens to ECF if drinks too much water?

A

water gained (only) by ECF

ECF osmolarity decreases to ~ 240 mosmol/L

now difference ECF 240 vs. ICF 285 mosmol/L

32
Q

where does water move to during hyperhydration XS drinking? what will happen to the cells?

A

water moves to higher osmolarity

from ECF to ICF (cells) until balanced

cells are BIGGER

ECF osmolarity has to be controlled!!

33
Q

what do TBW changes alter?

A

plasma (ECF) osmolarity

34
Q

TBW changes alter plasma (ECF) osmolarity

hows it detected?

A

by osmoreceptors in hypothalamus (brain)

35
Q

TBW changes alter plasma (ECF) osmolarity

what does osmoreceptors in hypothalamus (brain) stimulate?

A

pituitary gland to secrete more/less ADH

36
Q

TBW changes alter plasma (ECF) osmolarity

what does ADH alter?

A

permeability of renal collecting duct (CD)

37
Q

what balance initial change in TBW?

A

water retained/excreted

  • > plasma osmolarity stable
  • > cell volume stable
38
Q

wheres ADH Synthesis?

A
  • in cell body of central neurons (hypothalamus)

- axonal transport to posterior pituitary

39
Q

where ADH release?

A
  • in posterior pituitary

- into bloodstream (“neurosecretion”)

40
Q

what hormone comes from the posterior pituitary?

A

ADH

41
Q

whats the two major stimuli for release of ADH?

A
  1. increased ECF osmolarity

2. decreased blood volume

42
Q

two major stimuli for release

  1. increased ECF osmolarity
  2. decreased blood volume

whats the actions?

A
  1. inserts water channels (aquaporins) in luminal membrane of CD
  2. increases H2O reabsorption in the collecting duct
43
Q

whats obligatory water reabsorption?

A
  • not regulated!!

- accounts for 92% of total water reabsorption

44
Q

whats facultative water reabsorption?

A
  • tight epithelia
  • only transcellular
  • regulated by ADH
  • accounts for 2-8% of total water reabsorption
45
Q

water re-absorption - CCT

whats diuresis?

A

without ADH
excessive urine
large volume of diluted urine

46
Q

water re-absorption - CCT

whats anti-diuresis?

A

with ADH

small volume of concentrated urine

47
Q 
The urine osmolarity is
A. high without ADH.
B. independent of plasma osmolarity.
C. controlled by the pituitary gland.
D. independent of ADH.
E. high in diuresis.
A

C. controlled by the pituitary gland.

48
Q

What drives and regulates body water homeostasis?

A
  • distribution (ECF, ICF, plasma and interstitium)
  • composition in ECF and ICF
  • balance (input = output, kidney)
  • sodium/water re-absorption in the nephron
  • body osmolarity (hypothalamus, pituitary gland, ADH, collecting duct, aquaporin 2)

HUBS192 (36 decks)

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