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Human Physiology > body water balance > Flashcards

body water balance Flashcards

1
Q

several reasons why body water status is important?

A
  1. forms saliva
  2. hellps deliver oxygen all over the body
  3. regulates body temp and water
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2
Q

what % of the body is water?

A

60-70%

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3
Q

how long can we survive without any water consumed?

A

100 hours

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4
Q

how much water do we lose during moderate intensity exercise?

A

1-2 litres

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5
Q

how much water loss will prompt systems to disfunction?

how much do we lose before we die?

A

2.1 litres

10%

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6
Q

what part of the body contains the least water and why?

A

adipose tissue - 10%

as fat 90% lipid

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7
Q

name some factors which affect daily water needs?

A 
climate
clothing
activity levels
age
gender
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8
Q

what is the definition of total body water?

A

fluid that occupies intracellular and extracelular spaces

60% of body mass

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9
Q

what is the definition of intracellular volume?

A

fluid within tissue cells

40% of body mass

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10
Q

what is the definition of extracellular volume?

A

all fluids outside of cells

20% of body mass

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11
Q

what are the 2 parts of extracellular volume?

A
  1. interstitial fluid volume - located in spaces between tissue cells
    1% of body mass
  2. plasma volume - liquid portion of blood
    4% of body mass
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12
Q

what are the 2 semi-permeable membranes which separate intracellular and extracellular fluids?

A
  1. plasma membrane separates ICF from surrounding interstitial fluid
  2. blood vessel wall (capillaries) divide interstitial fluid from plasma
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13
Q

what is osmosis?

A

the net movement of solvent molecules through a partially permeable membrane from region of low solute concentration to high solute concentration

  • water molecules not solute molecules move *
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14
Q

difference and examples of solvent and solute?

A

solvent - substance that dissolves a solute - water

solute - substance dissolved in a solvent - glucose and electrolytes

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15
Q

what is osmolaLity?

A

number of osmoles of solute per kg of solution

high osmolality = high concentration of solute in solution

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16
Q

what is osmolaRity?

A

number of osmoles of solute in a litre of solution

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17
Q

how do you measure the body’s water status?

A

measuring osmolality
measures bodys electrolyte-water balance

plasma, saliva or urine sample

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18
Q

what is euhydration?

A

state of normal body water level

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19
Q

what does plasma osmality = ?

A

285-290

20
Q

what is hypohydration?

A

state of reduced body water level

21
Q

what is urine osmolality when hypohydration and the max in severe dehydration?

A

usually more than 700

1200 in severe dehydration

22
Q

what is hyperhydration?

A

state of elevated body water level

23
Q

what is urine osmolality during hyperhydration?

A

less than 700

minimum is 50

24
Q

what are the functions of electrolytes?

A
  1. control osmosis of water between body fluid compartments
  2. maintain acid-base balance
  3. carry electric current
  4. serve as cofactors
25
Q

what is the most abundant cation and anion (electrolytes) in ECF?

A

cation - Na+ (90%)

  • muscle contraction
  • fluid-electrolyte balance as accounts for 1/2 of osmolality of ECF
  • main electrolyte lost in sweat

anion - Cl-
- osmotic pressures

26
Q

what is the most abundant cation and anion (electrolytes) in ICF?

A

cation - K+

  • resting and action membrane potential
  • regulation of pH

anion - proteins and phosphates

27
Q

what is sodium control of water distribution a result of?

A

only cation which exerts significant osmotic pressure

sodium ions leak into cells and pumped out

28
Q

how do sodium losses occur?

A

through urine and perspiration

29
Q

what happens when there’s an increased conc of Na+ in ECF?

A

osmoreceptors stimulated

increased ADH released so increased thirst

decreased urinary water lost and increased water gain

additional water dilutes ECF and volume increased

30
Q

what is ADH released from and what is its secretion stimulated by?

A

released from posterior pituitary

secretion stimulated by exercise, plasma osmolality increase and plasma volume decreasing

31
Q

what does ADH promote?

A

water retention in the kidney (by making collecting duct highly permeable to water to reduce amount in urine) in an effort to dilute plasma electrolyte concentrations

32
Q

how does the body reduce water content of blood?

A

pituitary releases little ADH (collecting ducts not permeable to water)

low volume of water is reabsorbed by kidney

high volume of dilute urine passed into bladder

low volume of water passes into blood

33
Q

describe aldosterone?

released by

secretion stimulated by

A

released from adrenal cortex

secretion stimulated by:
decrease in plasma sodium, blood volume and pressure
increase in plasma K conc
renin-angiotensin mechanism

34
Q

what is the role of aldosterone?

A

promotes renal reabsorption of sodium, causing body to retain sodium

release reaches kidneys

when aldosterone secretion increases, sodium reabsorbed in collecting duct (increased fluid retention)

35
Q

describe ANP?

A

synthesised, stored and released by atrial myocyctes

in response to:
atrial distension
endothelin
sympathetic stimulation

36
Q

how does ANP reduce blood pressure and volume?

A

by inhibiting release of ADH, renin and aldosterone, and directing causing vasoldilation

37
Q

what is hypoatremia?

A

Na+ conc below normal range of 130 mmol/L

early symptoms: vomiting

later: seziures, coma and death

38
Q

what are the 2 main hormones that help regulate plasma osmolality?

A

ADH and aldosterone

39
Q

does dehydration impair performance if exercise is less than an hour?

A

NO

40
Q

what contributes to water input at rest?

A

fluid intake
food intake
metabolic water production

41
Q

what is sweat rate dependent on?

A
  1. body size
  2. absolute VO2
  3. aerobic fitness
  4. heat acclimatisation
  5. environment
  6. amount of muscles being used
42
Q

what does sweat loss =

A

change in mass + fluid intake - urine

43
Q

what does sweat rate =

A

sweat loss/time

44
Q

what are the cellular consequences of deydration?

A

loss of solutes/reduced blood volume
change in osmotic pressure
cells lose water and shrink due to osmossis

45
Q

how to calculate dehydration percentage?

A

(mass loss/pre-mass) x100

46
Q

what characteristics does an optimal sports drink have?

A

absorbs rapidly

maintains extracellularfluid volume and osmolality

no gastrointestinal distress

47
Q

advantages of isotonic, hypo and hypertonic solutions in a sports drink and what do they mean?

A

isotonic - balanced conc of solutes and water
- easily absorbed and quickly leaves stomach

hypotonic - low conc of solutes
- less easily absorbed but useful in hot weather

hypertonic - high conc of solutes
- too long to leave stomach and dehydration as need water to dilute in stomach

Human Physiology (9 decks)

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