lecture 34 Flashcards
how much of our body mass in water
40-70%
how does hydration help with thermoregulation
specific heat, sweat and blood flow.
Hyperhydration
more than normal
Euhydration
normal
Hypohydration
less than normal
Blood pressure receptors:
detect venous & arterial pressures
Osmoreceptors:
1% more in ECF osmolality will decrease urine production.
2% stimulates thirst.
which receptor will be stressed by exercise
both
what are the intravascular components
plasma volume (3.5 litres) and red blood cell volume (2 litres)
extravascular component of blood
ISFV around 12 litres (in muscle cells and sweat glands)
extra-vascular ICFV around 27-5 litres. (around muscle cells and osmoreceptors)
i
how precise is the daily body fluid balance maintained?
precisely. usually < 0.5 L/day
body fluid turnover.
2.5 L/day in temperate/inactive
~ 12+ L/day possible (exercise & heat)
how does osmolarity effect sweating
increase osmolarity will inhibit sweating.
Hypernatraemic
High sodium concentration in the blood, often due to inadequate water intake relative to sodium los
Hyponatraemia
Low sodium concentration in the blood, often due to excessive water intake or significant sodium loss through sweat.
why do you need to keep water and sodium balanced
you need to make sure you do not have too much of one without the other, can be fatal.
how can it be fatal
Performance: e.g., decrease volume decrease sustainable aerobic power.
Health: e.g., dilute ECF is readily fatal (=hyponatraemia)
what is the sweat rate in exercise
0.4-2 L/hour
how much can the stomach empty water
1 L/ hour. huge indivdual variation with this.
slide 3b
