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Nutritional Biochem 2 > Water > Flashcards

Water Flashcards

1
Q

What is the major constituent of cells, tissues, and organs and is vital for life?

A

Water

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2
Q

Water constitutes how much percentage of the body composition in males? What about in females?

A
  • Males: 50-65% [60%]

- Females: 40-55% [50%]

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3
Q

In males, how much of the 60% of fluids is intracellular vs. extracellular?

A
  • Intracellular fluid [2/3] (ICF)

- Extracellular fluid [1/3] (ECF)

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4
Q

Is the percentage of body water higher in infants and children than that of adults?

A

YES

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5
Q

Lean body mass is how much percentage water? How about fat body mass?

A
  • Lean - 80% H20

- Fat - 10% H20

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6
Q

What is often forgotten by dieticians in dietary recommendations?

A

Water

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7
Q

What is the only liquid nutrient that is really, and truly essential for body hydration and is vital for the body to function properly?

A

WATER

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8
Q

Water can be used as a SOLVENT, REACTION MEDIUM, REACTANT, and a REACTION PRODUCT. Here are brief descriptions as to how this happens…

A
  • Solvent - glucose and amino acids
  • Reaction Medium - allows enzymes to bind different molecules
  • Reactant - hydrolysis of peptides/disaccharides etc.
  • Reaction Product - oxidative metabolism of H+ containing substrates [ox phos produces ~300ml of water per day]
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9
Q

Water as a carrier… What are 3 basic things water will do as a carrier?

A
  1. Cellular homeostasis, removes waste from cells [Urea, Ammonia]
  2. Exchange in cells, interstitial fluid, capillaries
  3. Maintain vascular volume, allow blood circulation
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10
Q

Water and thermogenesis… What are 3 things that water will do coupled with thermogenesis?

A
  1. Limits changes in warm or cold environment
  2. Large vaporization capacity, allows loss of heat from body when ambient temp is still high.
  3. Sweating elicited, evaporation of water form the skin is efficient way to dissipate heat
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11
Q

Water as a lubricant and shock absorber… What are 3 things that water will do as a lubricant and shock absorber?

A
  1. Forms lubricating fluids for joints, saliva, gastric, intestinal etc.
  2. Maintains cellular shape, shock absorber for walking/running
    3. Important for brain and spinal cord (THE CSF) and is particularly important for the fetus who is protected by a water cushion.
    [Choroid plexus of the third ventricle, ependymal cells make the fluid]    *
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12
Q

Precise regulation of water balance over a 24 hr period is regulated within what percentage of body weight?

A

0.2%

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13
Q

Total water inputs for sedentary adults on average is…

A

2-3L

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14
Q

What helps to increase H20 for kids?

A

Fruits and veggies

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15
Q

Where is the majority of water absorbed? [hint: organ]

A

Small intestine [15L/day] Colon [5 L/day]

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16
Q

What is another crucial water input for the body?

A

Coupling of Water and Na+ reabsorptions and AQUAPORINS

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17
Q

What percentage of water is lost daily? Via what?

A
  • 5-10%

- Via, lungs, skin, kidneys

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18
Q

How much water loss is equivalent to 2.2 lbs of body mass?

A
  • 1L
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19
Q

If there is a complete lack of water consumption throughout the day, obligatorily, how much water will still be lost in the urine?

A

450 ml

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20
Q

What is the range of total daily fluid requirements?

A

As little as 2 L/day - 16 L/day

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21
Q

Evaporation of water by way of sweat on the skin is efficient for removing heat, how many kJ is lost by the evaporation of 1 g of water?

A

2.2 kJ

22
Q

If one is exercising in a hot environment, how much water can be lost?

A

2-3 L/hr [4-7 lbs of body weight]

23
Q

Comparing sweat to plasma or extracellular fluid, what is sweat considered?

A

Hypotonic

24
Q

Intense sweating leads to greater water loss than electrolyte loss and can lead to what type of dehydration?

A

Hypertonic dehydration

25
Q

What is more important during exercise, fluid or salt replacement?

A

Fluid

26
Q

What happens to osmotic pressure when water losses exceed the intake of water? [hint: what happens to extracellular fluid?]

A

Extracellular fluid increases

27
Q

Through activation of hypothalamic osmoreceptors, what hormone is released, and from what part of the pituitary?

A

- ADH/Vasopressin
- Posterior pituitary gland
[Aldosterone INCREASES sodium uptake!]
[Posterior Pituitary creates Aquaporin]

28
Q

What is the single most important stimulus that controls thirst?

A

- The osmoreceptor input

29
Q

When an individuals thirst is quenched, what tells the body that it is not thirsty anymore?

A
  • Negative feedback system, stating thirst has been quenched
30
Q

Is there a gold standard for measurement/assessment of dehydration?

A

NO, which is what makes identifying it difficult!

31
Q

When using body weight to assess hydration status, how does it compare to urine and blood assays?

A
  • Body weight change is the most universal, economical and feasible surrogate to body water change
32
Q

Where is the urine color chart used?

A

- It is used in nursing homes and hospitals because it is a low cost and rapid method for assessing hydration status, which can help in early intervention

33
Q

What is the best time of day to use a urine color chart and to assess hydration levels?

A
  • Anytime, but first morning void is NOT VALID
34
Q

If one has high grades of color [7 or 8] what can this be instead of high urine concentrations?

A
  • Gross hematuria or bilirubin excretion because of jaundice
35
Q

Which urine indices is more reliable, urine osmolarity or plasma osmolarity?

A
  • Urine osmolarity is inferior to that of plasma osmolarity in the detection of dehydration
36
Q

Plasma osmolarity is tightly contrilled and rarely varies more than 1% around what set point?

A

280 mmol/Kg

37
Q

A plasma osmolarity greater than what value is indicative of dehydration?

A

300 mmol/Kg

38
Q

What type of measurement is used to approximate the hydration status with a 10-cm scale?

A

Visual analog scale [pretty reliable within pt. populations]

39
Q

When a patient presents with tenting of the skin, aka. reduced skin turgor, what does this tell the clinician?

A

red flag: dehydrated patient

40
Q

What is better at measuring hydration status, BIA or BIS?

A

BIS, bioelectrical impedence analysis is prone to reduced reliability and accuracy via alcohol consumption, diuretics, menstrual cycle illness

41
Q

When using the tracer method of measuring hydration status, what compund is used specifically?

A
  • Deuterium oxide, this is a stable isotope of hydrogen
  • calculates dilution of tracer volume
    [These are used mainly in RESEARCH, not clinical practice]
42
Q

What are the levels of mild, moderate, severe dehydration?

A

mild - 1-2% loss body weight
moderate - 2-5% body weight
severe - >5% body weight

43
Q

What are the 3 types of dehydration, and give a brief description of each…

A
  1. Isotonic dehydration - net salt and water loss are equal (diarrhea, inadequate fluid and salt intake)
    * 2. Hypertonic dehydration - most common in ADULTS, loss of water or excess of salt (Hypernatremia; Na+ > 145 nmol/L)*
  2. Hypotonic dehydration - most common in children and infants, loss of salt or excess of water (hyponatremia; Na+ <135 nmol/L)
44
Q

What are the 6 major factors leading to dehydration of the elderly?

A
  • 1. Blunted sensation of thirst (hypodipsia)
    2. Osmoreceptor and baroreceptor defects
    3. Decresed renal ability to concentrate urine, resistance to ADH, low aldosterone secretion
    4. Difficulties gaining access to fluids, swallowing issues, cognition, oral sedative usage
    5. Diuretics/Laxatives increasing water loss
    6. Fear of incontinence, limit liquid intake    *
45
Q

What does the american college of sports say the minimum amount of dehydration that will start to compromise physiological function and impair exercise performance capacity?

A
  • It only takes 2%!!!!
46
Q

Children start their school day with what type of deficit

A

- HYDRATION DEFICIT!

[66% of kids are dehydrated in the AM, 2/3 of schoolchildren]

47
Q

Half of a glass of water, 115ml, is equivalent to what fruit?

A

A medium sized apple… [this is crazy]

48
Q

Drinking to thirst (STUPID IOM) is not recommended nor advised for which conditions?

A

Cogestive heart failure, end stage renal disease and COPD… fluid restriction is ADVISED for these conditions

49
Q

How does one achieve hyperhydration?

A
  • ingesting excess water combined with glycerol to create an osmotic gradient for temporary water retention
50
Q

How does one achieve hyponatremia (aka. water intoxication)

A
  • When blood sodium concentration falls to abnormally low levels (<135mmol/L) causing swelling in the brain, leading to seizures, coma, and death.
    [Drinking more fluid than the amount lost in sweat is a key risk factor for hyponatremia, but it can also occur in dehydrated athletes during prolonged exercise in hot climates as a result of large sodium losses in sweat]

Nutritional Biochem 2 (6 decks)

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