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Renal and Urology > Physiology 1 > Flashcards

Physiology 1 Flashcards

1
Q

what is osmolarity

A

the concentration of osmotically active particles in a solution

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2
Q

units of osmolarity

A

osmol/l or mosmol/l

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3
Q

mosmol/l can be used

A

for weak salt solutions i.e. body fluids

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4
Q

osmolarity can be calculated if what 2 factors are known

A
  1. the molar concentration of solution

2. the number of osmotically active particles present in the solution

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5
Q

e.g 150mM NaCl work out its osmolarity

A
  • molar concentration= 150mM
  • number of osmotically activity particles: Na+Cl= 2

osmolarity= 2x150= 300 mosmol/l

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6
Q

osmolarity vs osmolality

A

osmolality is the concentration of osmotically active particles per kg

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7
Q

units of osmolality

A

osmol/kg water

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8
Q

for weak salt solution the terms osmolarity and osmolality are

A

interchangeable

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9
Q

tonicity

A

is the effect a solution has on cell volume

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10
Q

tonicity of solutions can either be

A
  • hypertonic
  • hypotonic
  • isotonic
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11
Q

isotonic

A

the solution has the same osmolarity as the osmolarity of the fluid inside the cell, there will be no net movement of water into or out of the cell

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12
Q

hypotonic

A

the solution has a lower osmolarity than the osmolarity of the fluid inside the cell, there will be a net movement of water into the cell

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13
Q

hypertonic

A

the solution has a higher osmolarity than the osmolarity of the fluid inside the cell, there will be a net movement of water out of the cell

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14
Q

although related to osmolarity tonicity

A

also takes into consideration the ability of a solute to cross the cell membrane

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15
Q

total body water

A
  • 60% of body weight in males

- 50% of body weight in females

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16
Q

total body water exists as 2 major compartments

A

intra-cellular fluid (67% of total body water) and extra-cellular fluid (33% of total body water)

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17
Q

extra-cellular fluid includes

A
  • interstitial fluid (80% of ECF) which is the fluid in spaces between tissue cells
  • plasma fluid (20% of ECF) which is the fluid portion of the blood
  • transcellular fluid and lymph fluid is negligible
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18
Q

how do you measure the volume of body fluid compartments

A

using tracers

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19
Q

how do tracers work

A

you can determine the volume of distribution of a tracer substance

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20
Q

useful tracers

A
  • total body water= 3H20
  • extra-cellular fluid= Inulin
  • Plasma= labelled albumin
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21
Q

total body water equals

A

the extra-cellular fluid plus the intra-celualr fluid therefore, if you use tracers to work out the total body volume and ECF you can calculated the ICF

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22
Q

worked example

A
  • imagine adding a dose of tracer (D=42MG) to a container containing a large and unknown volume of water (V)
  • you mix the tracer allowing it to equilibrate
  • you then take a small sample volume from the container( (5ml) and measure the concentration of tracer (C) in this sample
  • on analysis c= 0.005mg/5ml= 1mg/litre
  • so the volume of water in the container= DOSE/ SAMPLE CONC
  • VOLUMEN= 42/1= 42 LITRES
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23
Q

Summary for working out volume of distribution

A
  1. add a known quantity of tracer X into the body (Qx: mol or mg)
  2. measure the equilibrium CONCENTRATION of X in the body (X)
  3. Volume of distribution= Qx/ X
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24
Q

for water balance

A

inputs have to equal outputs

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25
Q

water input

A
  • fluid intake= 1200ml/day
  • food intake= 1000 ml/day
  • metabolism= 300 ml/day
26
Q

water output

A

insensible loss:

  • skin= 350ml/day
  • lungs= 350ml/day

sensible losses:
sweat= 100ml/day
faeces= 200ml/day
urine= 1500ml/day

27
Q

total input and total fluid output

A

input is 2500ml per day and output is 2500ml per day

28
Q

water imbalance is manifested as

A

changes in body fluid osmolarity

29
Q

water loss in hot weather

A
  • skin= 350ml
  • lungs= 250ml
  • sweat= 1400ml
  • faces= 200ml
  • urine= 1200ml
30
Q

water loss in prolonged heavy exercise

A
  • skin= 350ml
  • lungs= 650ml
  • sweat= 5000ml
  • faeces= 200ml
  • urine =500ml
31
Q

in hot temperatures and during prolonged heavy exercise

A

water balance is maintained by increasing water ingestion, decreased water excretion is not sufficiency to maintain water balance

32
Q

ionic component of the intra-cellular fluid

A

10mM Na+
140mM K+
7mM Cl-
10mM HCO3-

33
Q

ionic components of the extra-cellular fluid

A

140mM Na+
4.5mM K+
115 mM Cl-
28 mM HCO3-

34
Q

ECF and the ICF are separated by

A

compartments

35
Q

the cell membrane and membrane transport mechanisms all

A

cell to maintain internal environments that are different to there surrounding

36
Q

main ions in the ICF

A

K+, Mg2+ and negatively charged proteins

37
Q

main ions in the ECF

A

Na+, Cl- and HCO3-

38
Q

Cell membranes

A

are selectively permeable but despite this the osmotic concentrations of both ECF and ICF and identical (300mosmol/litre)

39
Q

because changes in the solute concentration lead to

A

immediate changes in water distribution, the regulation of fluid balance and electrolyte balance are highly intertwined

40
Q

fluid shift

A

movement of water between the ICF and ECF in response to an osmotic gradient

41
Q

Challenges to fluid homeostasis

A
  1. Gain or loss of water
  2. Gain or loss of NaCl
  3. Gain or loss of isotonic fluid
42
Q

gain or loss of water

A

change in fluid osmolarity causes similar changes in the ICF and ECF (both either increase or decrease)

43
Q

gain or loss of NaCl

A

Change in fluid osmolarity causes
A) Na+ to be excluded from the ICF
B) osmotic water movements

both of these factors combine to produce opposite changes in ICF and ECF volumes

44
Q

ECF NaCl gain

A

increased extra-cellular fluid volume

reduced intra-cellular fluid volume

45
Q

ECF NaCl loss

A

reduced extra-cellular fluid volume

increased intra-cellular fluid volume

46
Q

gain or loss of isotonic fluid

A

(e.g 0.9% NaCL) causes no change in fluid osmolarity only the ECF volume falls

47
Q

the kidneys alter

A

the composition and volume of the ECF, regulation of ECF is vital for long term control of blood pressure

48
Q

electrolyte balance occurs when

A

rate of gain= rate of loss

49
Q

electrolyte balance is important for 2 reasons

A
  1. Total electrolyte concentrates can directly alter water balance
  2. the concentrations of individual electrolytes can affect cell function
50
Q

Na+ and K+ are particularly important because

A
  1. they are major contributors to the osmotic concentration of ECF and ICF respectively
  2. they directly affect the functioning of cells
51
Q

sodium balance

A

more than 90% of the osmotic concentration of the ECF results from the presence of sodium salts

52
Q

the total amount of sodium in the ECF represents

A

a balance between 2 factors (input and output)

53
Q

Na+ is mainly present

A

in the ECF therefore it is a major determinant of ECF volume (water follows sodium)

54
Q

Minor fluctuations

A

in plasma potassium (K+) can have detrimental consequences

55
Q

potassium plays a key role in

A

establishing membrane potential

56
Q

95% of the bodies potassium is

A

intra-cellular so small leakages or increased cellular uptake may severely affect K+ plasma concentrations leading to

  • muscle weakness causing paralysis
  • cardiac irregularities causing cardiac arrest
57
Q

salt balance

A

for balance to occur input has to equal output

58
Q

intake of salt

A

fluids and food= 10.5g/ day

59
Q

output of salt

A
  • sweat and faeces= 0.5g/day

urine= 10g/day

60
Q

salt imbalance is manifested as

A

changes in the extra-cellular fluid volume, regulation of extra-cellular fluid volume is very important for the long term regulation of blood pressure

Renal and Urology (51 decks)

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