Water balance Flashcards
why does an overweight person have a lower relative water content than a normal weight person
Fat is the least well hydrated of all the major tissues
around 10% water whereas others are >70%
If a greater proportion of their body is adipose tissue then a greater proportion of their body has limited water content
in the body what is the ratio of intracellular fluid to extracellular fluid
Name the two type of extracellular fluid
2/3 intra : 1/3 extra
intersititial fluid
intravascular fluid
name 3 methods of water entering the body
fluid intake
food intake
metabolic water
name 5 methods of water leaving the body
urine faecal loss expired air skin loss sweat loss
explain the difference between sensible and non-sensible water loss
sensible is loss that you can feel/are aware is happening
define the terms: euhydration hyperhydration hypohydration dehydration
a state of water balance
physiological state of excess body water
physiological state of decreased body water content
the process of losing body water
explain why euhydration is never considered to be completely stable
fluctuates around a set point
because don’t take water in at the exact point when it is lost, will fluctuate slightly above and slightly below depending on if drinking or not
give the values for the following variables which would indicate that someone is euhydrated
plasma osmolality
urine osmolality
urine specific gravity
<290 mosmol/kg
< 700mosmol/kg
<1.02
what senses a change in osmolality and what structure controls the response
osmoreceptors
hypothalamus
why do re-hydration strategies aim to manipulate the fall in ADH caused by drinking
if can make ADH fall less dramatically then more of the drink will be retained and therefore re-hydration will be more efficient
how can the rate of drinking be manipulated to increase the retention of a drink
bolus vs metered drinking
metered produced less urine which suggests that more of the drink is being retained
how can the volume of drink consumed, relative to the amount of water lost in exercise be altered to improve hydration
greater volume = better hydration
150% to 200% needed to achieve a net positive fluid balance
no further benefit of increasing from 150% to 200%
how can the addition of solute be used to increase the retention of a drink
addition of Na+ = better fluid balance
more Na+ = more drink retained, but also too much will make drink too salty
higher Na+ = increased osmolality = increased adh
how can the addition of macronutrients to drinks increase how well they hydrate someone
increasing glucose content from 2% to 10% = better retention of fluid balance
addition of milk protein = better fluid balance
(addition of whey didn’t)
