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Human Physiology > W2 - Hydration > Flashcards

W2 - Hydration Flashcards

1
Q

What % of the MALE body is water?

A

60-80%

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2
Q

What % of the FEMALE body is water?

A

50-60%

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3
Q

How long can you survive without water?

A

100hrs

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4
Q

How many litres per hour is the typical sweat rate during exercise at normal body temp?

A

1-2

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5
Q

What % of H20 is in fat?

A

10

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6
Q

What % of H20 is in muscle?

A

75

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7
Q

Reasons why H20 is important

A

Lubricates joints

Flushes out waste products

Allows cells to grow, reproduce + survive.

Keeps mucosal membranes moist

Contributes to saliva

Regulation of body temp

Respiration

Blood flow

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8
Q

What factors affect daily H20 needs?

A

Climate

Clothing

Activity levels

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9
Q

Median of observed values for daily H20 needs

A

H20 balance studies

H20 turnover studies

H20 intake studies

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10
Q

What are the organic substances that make up the bodys fluids?

A

Glucose

aa

FA

Hormones

Enzymes

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11
Q

What are the inorganic substances that make up the bodys fluid?

A

Na+

K+

Ca2+

Magnesium

Chloride

Phosphate

Sulphate

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12
Q

When does fluid balance exist?

A

When total H20 intake = total H20 loss

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13
Q

Input for body H20 balance

A

Food

Fluids

Metabolism

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14
Q

Output for body H20 balance

A

Urine

Faeces

Skin

Lungs

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15
Q

How much of the total body water belongs to intracellular fluid?

A

40%

0.4 L/Kg

28L (for a 70kg male)

2/3rd of total body water, being 42L.

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16
Q

How much of the total body water belongs to extracellular fluid?

A

20%

14L (for a 70kg male)

1/3rd of total body water, being 42L.

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17
Q

What can extracellular fluid be divided into?

A

Plasma

Interstitial fluid

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18
Q

What separates the ICF from surrounding interstitial fluid?

A

Plasma membrane

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19
Q

What divided the interstitial fluid from the plasma?

A

Bv wall

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20
Q

Solute

A

Substance dissolved in a solvent

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21
Q

What machine measures osmolarity?

A

Cryoscopic osmometer

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22
Q

Define osmolaLity

A

No. of osmoles (Osmol) of solute per kg of solution

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23
Q

Define osmolaRity

A

No. of osmoles (Osmol) of solute in a L of solution

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24
Q

What fluids does the Cryoscopic osmometer commonly measure?

A

Saliva

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25
Q

Define euhydration

A

State of normal body H20 level

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26
Q

What is plasma osmolality in euhydration?

A

285-290 mOsmol.kg-1

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27
Q

What can hypo hydration result in for urine?

A

High urine osmolality

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28
Q

Define hypo hydration

A

State of red. body water level w/in the cell

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29
Q

What is max urine osmolality in severe dehydration?

A

1200 mOsmol.kg-1

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30
Q

Hypertonic

A

Fluid around cell has a higher solute conc

= H20 diffuses OUT of cell

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31
Q

Hypotonic

A

Fluid around cell has a lower solute conc

= H20 diffuses INTO cell

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32
Q

Hyperhydration

A

State of elevated body water level in cell

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33
Q

Electrolytes

A

Substances that produce an electrically conducted solution when dissolved in a polar solvent.

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34
Q

What do the dissolved electrolytes do when in the solution?

A

Separate into cations + anions.

Then disperse uniformly through solvent causing a change in concentration.

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35
Q

Functions of electrolytes

A

Control osmosis between compartments of the body.(ECF + ICF)

= Helps maintain pH

Carry electrical current

Serve as cofactors

AP generation

Cardiac rhythm control

Muscle contraction

Energy storage

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36
Q

ELECTROLYTES

Whats the most abundant cation in extracellular fluid?

A

Na+

90% of extracellular cations

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37
Q

ELECTROLYTES IN ECF

Functions of Na+

A

Muscle contraction

Impulse transmission

Fluid + electrolyte balance

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38
Q

ELECTROLYTES

Whats the most abundant anion in extracellular fluid?

A

Cl-

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39
Q

ELECTROLYTES IN ECF

Functions of Cl-

A

Regulates osmotic pressure

Forms HCL

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40
Q

ELECTROLYTES

Whats the most abundant cation in ICF?

A

K+

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41
Q

ELECTROLYTES IN ICF

Functions of K+

A

Resting membrane potential

AP

Maintains intracellular vol

Regulation of pH

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42
Q

ELECTROLYTES

Whats the most abundant anion in ICF?

A

PO4(3-)

Phosphate

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43
Q

ELECTROLYTES IN ICF

Functions of PO4(3-)

A

PTH (Parathyroid hormone) regulation

Blood calcium levels

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44
Q

Na+ is the main electrolyte lost in sweat.

At what concentration?

A

40-50mmol/L

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45
Q

Why does sodium control water distribution?

A

Only cation to exert osmotic pressure

Na+ leaks into cells + then pumps vs their electrochemical gradient

[Na+] in ECF remains stable

Losses occur through urine + perspiration

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46
Q

Where are osmoreceptors?

A

Hypothalamus

47
Q

What do osmoreceptors do?

A

Send signals to posterior pituitary gland = ADH released.

48
Q

What is secretion of ADH from the pituitary gland from the osmoreceptors stimulated by?

A

Haemoconcentration (i.e during exercise)

⬆️ plasma osmolality

⬇️ plasma volume

49
Q

What does Haemoconcentration result in?

A

⬆️ blood viscosity

50
Q

What is Haemoconcentration caused by?

A

Dehydration

Artificially induced by blood doping

51
Q

What does ADH do?

A

Promotes H20 retention in the kidney to dilute plasma electrolyte concentrations.

52
Q

How does the kidney enable H20 retention?

A

Collecting ducts become highly permeable to H20

53
Q

What is aldosterone?

A

Mineralocorticoid hormone

54
Q

Mineralocorticoid hormones

A

Class of steroid hormones that reg salt + H20 balances

55
Q

Where is aldosterone released from?

A

Adrenal cortex

56
Q

What is secretion of aldosterone stimulated by?

A

⬇️ plasma sodium

⬇️ blood vol

⬇️ bp

High plasma potassium

57
Q

What does aldosterone do?

A

Controls Na+ + K+ excretion

58
Q

According to Goulet, 2012, when doesn’t loss of water appear to impair performance?

A

When duration is less than 1hr

59
Q

According to Cheuvront + Kenefick, 2014, when is endurance performance impaired - associated to loss of water?

A

When losses are 2% + body mass

60
Q

What is the overall loss of water at rest?

A

96 ml/hr

61
Q

What is the overall loss of water during prolonged exercise?

A

1325 ml/hr

62
Q

Factors affecting sweat loss

A

Body size

Absolute VO2

Aerobic fitness

Heat acclimatisation

Env

63
Q

How is sweat loss calculated?

A

Change in mass + fluid intake - urine

64
Q

Cellular consequences of dehydration

A

Loss of solutes

⬇️ blood vol

Change in osmotic pressure

Lose H20 = shrink

65
Q

Quantifying dehydration

A

Traditionally expressed as a % of body mass loss:

% dehydration or % hypo hydration

66
Q

Why don’t human always respond to physiological signs of thirst?

A

Dk benefits of fluid intake / not remembering to drink

Disliking H20

Lack of thirst

Lack of H20 availability

67
Q

CHO content for hypotonic sports drinks

A

1-3%

68
Q

CHO content for isotonic sports drinks

A

6-8%

69
Q

CHO content for hypertonic sports drinks

A

10%+

70
Q

Purpose for hypotonic sports drinks

A

Quickly replace fluid lost by sweat

71
Q

Purpose for isotonic sports drinks

A

Quickly replace fluid lost by sweat

Provide boost of CHO

72
Q

Purpose for hypertonic sports drinks

A

Supplement CHO intake

73
Q

What are the considerations for sports beverage optimisation?

A

Rate of absorption

Any gastrointestinal distress?

If maintains ECF + osmolality

Offers pot to ⬆️ performance

74
Q

What sports drink would be suggested for a 5-10km run?

A

Water or hypotonic sports drink

75
Q

Longer than 10km sports drink?

A

More of an isotonic sports drink

76
Q

Pre-exercise

How much H20?
When?

A

500ml = Adequate

1-2hr before exercise

77
Q

During exercise

If less than an hour, how much H20?

A

0.5 to 1L / hour

78
Q

H20 intake suggestion for events of more than 1hr

A

600-1200ML / hr

+ Na+ (0.5-0.7 g/L)

79
Q

What does inclusion of Na+ in fluid aid??

A

Fluid absorption in kidneys

Water retention

80
Q

What % of H20 do you need to drink of what you lost in exercise?

A

150%

81
Q

Why does alcohol increase the rate of urination?

A

Due to ⬇️ release of ADH

82
Q

What is variability in total body water primarily due to?

A

Differences in body composition

83
Q

Approx what % of total body water is turned over daily?

A

5-10%

84
Q

How is metabolic water formed?

A

By oxidation of substrates

85
Q

Total body water per kg of body mass from infancy to maturity

Why?

A

Infancy = Highest

Maturity = Lower

== Fluid regulatory mechanisms mature

86
Q

What are the 2 principle forms of body water deficit?

A

Hypertonic hypovolemia

Isotonic hypovolemia

87
Q

What is the physiology behind hypertonic hypovolemia?

A

Body H20 loss > solute loss (greater than)

H20 moves from ICF–> ECF

Partial restoration of ECF

88
Q

What is the physiology behind isotonic hypovolemia?

A

Isotonic body H20 + solute loss

NO net movement of H20 among body fluid compartments

89
Q

What are the complex markers for hydration assessment techniques?

A

Total body water (dilution)

Plasma osmolality

90
Q

What are the simple markers for hydration assessment techniques?

A

Urine concentration

Body mass

91
Q

Advantages of complex markers for hydration assessment techniques

A

Accurate

Reliable (gold standard)

92
Q

Disadvantages of complex markers for hydration assessment techniques

A

Analytically complex

Expensive

Req. baseline (for total body water)

Invasive (for plasma osmolality)

93
Q

Advantages for simple markers for hydration assessment techniques

A

Easy

Rapid

Screening tool

94
Q

Disadvantages for simple markers for hydration assessment techniques

Urine concentration

A

Easily confounded

Timing is critical

Freq + colour is subjective

95
Q

Disadvantages for simple markers for hydration assessment techniques

Body mass

A

Confounded by changes in body composition

96
Q

What other markers can be used under the hydration assessment techniques

A

Plasma vol

Plasma sodium

Fluid balance hormones

Bioimpedence

Saliva

Physical signs

Thirst

97
Q

What can be used to indirectly estimate urine osmolality?

A

Urine colour chart

98
Q

What can be used to directly assess urine osmolality?

A

Refractometer

99
Q

When using a cryoscopic osmometer what will a higher osmolality lead to?

A

Freezing point depression

100
Q

How can total body water be estimated?

A

Multi-frequency bioelectrical impedance analyser

– Indirect method

101
Q

What happens to the multi-frequency bioelectrical impedance analyser at low frequencies (5Hz)?

A

Current can’t penetrate cell membrane

Estimates extracellular H20 = 1/3rd of total body water

102
Q

What happens to the multi-frequency bioelectrical impedance analyser at high frequencies (200Hz)?

A

Current can penetrate cell membrane.

Estimates intracellular water = 2/3rds of total body water

103
Q

What does H20 pass through in osmosis?

A

Partially permeable membrane

104
Q

Calculation for urine osmolality

A

(160.48 x urine colour) - 150.48

105
Q

Step by step for the assessment of urine colour + osmolarity

A

Urine in container

Determine colour using urine colour chart

Estimate osmolarity using urine osmolality

Determine urine osmolarity using refractometer

106
Q

Step by step for the assessment of saliva osmolarity

A

Saliva in sampling tube

Determine urine osmolarity using cryoscopic osmometer

107
Q

Equation for plasma volume (L)

A

(0.042 x Lean Mass) + 0.578

Sawka et al., 1992

108
Q

Equation for interstitial volume (L)

A

Extracellular vol (L) - Plasma vol (L)

109
Q

What are the typical values for assessing hydration + body water

What % of BM does … count for?

  1. Total body H20
  2. Int. Cellular vol
  3. Ext. Cellular vol
  4. Interstitial vol
  5. Plasma vol
A

Total body H20 = ~60% body mass (BM)

Int. cellular vol = ~ 40% BM

Ext. cellular vol = ~ 20% BM

Interstitial vol = ~ 16% BM

Plasma vol = ~4% BM

110
Q

What is the bioelectrical impedance analysis based on?

A

Electrical conductance characteristics of hydrous (FF) + anhydrous (Fat component) tissues.

111
Q

What must subject do/not do prior to the bioelectrical impedance analysis?

A

NO food or drink in 4hrs b4

NO exercise 12hrs b4

NO alcohol 48hrs b4

NO diuretics w/in 7 days b4

Must have urinated w/in previous 30 mins

112
Q

In the bioelectrical impedance analysis, how long must the subject lie quietly for before repeating procedure?

A

5 mins

113
Q

In the bioelectrical impedance analysis, 4 electrodes are prepared w/ electro-conducting gel + attached to which sites on the foot?

A

Dorsal surface of right foot.
Proximal to 2nd metatarsal-phalangeal joint.

Anterior surface of right ankle between medial + lateral malleoli.

114
Q

In the bioelectrical impedance analysis, 4 electrodes are prepared w/ electro-conducting gel + attached to which sites on the RIGHT hand?

A

Proximal to dorsal surface of 3rd metacarpal-phalangeal joint.

Dorsal surface of wrist adjacent to head of ulna.

Human Physiology (16 decks)

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