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Year 2 > Bodily fluid compartments and challenges to homeostasis > Flashcards

Bodily fluid compartments and challenges to homeostasis Flashcards

1
Q

What is osmolarity?

A

Concentration of osmotically active particles in a solution

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2
Q

What are the units of osmolarity?

A

(M)osmol/l

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3
Q

Which two pieces of information are needed to calculate osmolarity?

A

Concentration of a solution

Number of osmotically active particles in a solution

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4
Q

How is osmolarity calculated?

A

Multiplying to concentration of a solution by it’s number of osmotically active particles

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5
Q

What is the difference between osmolality and osmolarity?

A

Units osmolality = osmol/kg and osmolarity = osmol/l (no difference when talking about weak salts)

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6
Q

What is the rough osmolarity of most body fluids?

A

300 mosmol/l

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7
Q

What is tonicity?

A

The effect a solution has on cell volume

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8
Q

What are the three types of tonicity and how do they affect cell volume?

A

Hypotonic - increase cell volume
Isotonic - no effect
Hypertonic - decrease cell volume

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9
Q

Is total body water high on average in men or woman? Why?

A

Men because they have less fat

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10
Q

What two compartments can total body water be broken down into?

A

Intracellular volume

Extracellular volume

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11
Q

What categories can extracellular fluid volume be broken down into?

A

Plasma
Interstitial (biggest proportion)
Transcellular
Lymph

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12
Q

What separates the intracellular and extracellular fluid compartments?

A

Cell membrane

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13
Q

How can the volume of body fluid compartments be measured?

A

Distribution volume of tracers

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14
Q

Name three useful tracers and which compartment they measure

A

Tritiated water - total body water
Inulin - extracellular fluid volume
Labelled albumin - plasma

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15
Q

How can intracellular fluid volume be measured?

A

If the volumes of the total body water and extracellular fluid are known intracellular fluid volume can be measured using the equation:
TBW = ECF + ICF

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16
Q

How can the volume of water in a container be measured using the dilution principle?

A

Add a dose of tracer to the fluid volume in question (the body) and allow equilibrium to be reached. Sample the fluid and measure the tracer concentration (equilibrium volume). Use this equation:

Volume = dose of tracer (mol) / sample concentration (mol/l)

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17
Q

In simple terms, what is homeostasis?

A

The maintenance of a variable within an acceptable range

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18
Q

What are the inputs and outputs involved in water balance?

A

Input - fluids, food, metabolism

Output - faeces, sweat, skin, lungs, urine

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19
Q

What is an insensible loss (in terms of water balance)? Give two examples

A

A loss of water which cannot be regulated by physiological means

Skin & lung water loss

20
Q

Water imbalance manifests as changes in fluid tonicity. T/F

A

False - changes in fluid osmolarity

21
Q

Can decreased excretion from the kidneys (i.e decreased urine output) maintain water balance alone?

A

No - physiological dysuria does not exist

22
Q

Describe the isotonic composition of the ICF and ECF repectively

A

ICF - high potassium, high magnesium and high negatively charged proteins
ECF - high sodium, high chlorine, high bicarbonate

23
Q

What allows the difference in environment between the ICF and ECF?

A

Proteins in the plasma membrane

24
Q

How do the osmotic concentrations differ between the ICF and ECF?

A

They don’t - both 300 mosmol/l

25
Q

Why is regulation of fluid balance and electrolyte concentration related?

A

Changes in solute concentrations cause changes in water distribution (osmotic gradient)

26
Q

Do kidneys regulate composition of ICF or ECF?

A

ECF

27
Q

What is fluid shift?

A

Movement of water between the ICF and ECF due to changes in the osmotic gradient

28
Q

What happens when the osmotic concentration of the ECF increases?

A

Concentration increase > hypertonicity > fluid loss from the ICF

29
Q

What happens when the osmotic concentration of the ECF decreases?

A

Concentration decreases > hypotonicity > fluid movement into the ICF

30
Q

List the three possible changes to fluid homeostasis

A

Gain/loss of water
Gain/loss of NaCl (salt)
Gain/loss of isotonic fluid

31
Q

What happens when there is a gain/loss of water?

A

Change in fluid osmolarity causes parallel changes in ICF and ECF volumes (both increase or decrease)

32
Q

What happens when there is a gain/loss of NaCl?

A

Change in fluid osmolarity causes opposite changes in fluid volumes in response to active transport of sodium into the ECF and osmotic gradient changes

33
Q

What happens when there is a gain of salt in the ECF?

A

ECF volume increases

ICF volume decreases

34
Q

What happens when there is a loss of salt in the ECF?

A

ECF volume decreases

ICF volume increases

35
Q

What happens when there is a gain/loss of isotonic fluid?

A

No change in fluid osmolarity but change in ECF volume

36
Q

Give an example of an isotonic fluid

A

0.9% saline

37
Q

Regulation of ICF volume is vital for long term blood pressure control. T/F

A

False - ECF volume

38
Q

Give two reasons why electrolyte balance is important?

A

Electrolyte concentrations affect water balance

Concentrations of individual electrolytes affect cell functioning

39
Q

What are the two most important electrolyte concentrations to maintain?

A

Sodium and potassium

40
Q

What is an electrolyte?

A

A substance which dissociates into free ions when put in solution

41
Q

What is sodium a major determinant of in terms of fluid balance?

A

ECF volume (water follows salt)

42
Q

Sodium is an accurate measure of the balance between input and output of water. T/F

A

True

43
Q

Minor fluctuations in plasma potassium can have serious affects. T/F

A

True

44
Q

Why must potassium concentration be so tightly regulated?

A

It is important for the membrane potential (K plasma)

45
Q

What are the two effects of deranged plasma potassium concentration?

A

Muscle weakness –> paralysis

Cardiac irregularities –> cardiac arrest

46
Q

What are the inputs and outputs of salt balance?

A

Input - diet

Output - sweat, faeces & urine

47
Q

How does salt imbalance manifest?

A

Changes in extracellular volume

Year 2 (72 decks)

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