Human Physiology Body Water and Osmosis

  1. How do you calculate Total Body Water (TBW)?
    TBW = 0.6 x body mass

    (a person is approx. 60% water)
  2. What factors account for variation in TBW?
    Primarily fat composition, but also muscle composition to a lesser degree AND it varies greatly with age (especially in kids)
  3. ECF = _______ TBW

    ICF = _______ TBW
    ECF = 1/3 TBW

    ICF = 2/3 TBW
  4. Plasma = ________ ECF

    Interstitial fluid = _________ EFC
    Plasma = 1/5 ECF

    Interstitial fluid = 4/5 ECF
  5. How does water move between ECF and ICF compartments?
    the cell membrane and capillary wall are quite permeable to H20 via aquaporins.

    Water will move IF there is a difference in osmolarity

    "Water goes where the osmolytes are"
  6. Define OSMOSIS
    Water moves from its area of high concentration to low through semi-permeable membranes
  7. Define OSMOLALITY
    osmoles / kg solvent
  8. Define OSMOLARITY
    osmoles / L solution
    (π=RTC) the amount of external pressure needed to prevent the entry of water

    • π is osmotic pressure
    • R is universal gas constant
    • T is temp in K
    • C is solute concentration in Osm/L
  10. Define VASOPRESSIN
    (aka anti-diuretic hormone) released by brain and changes aquaporin activity in the kidneys to pull water back into the body
  11. Define ALDOSTERONE
    released by adrenal cortex and increases Na+ reuptake in kidney (and water, which follows Na+)
Card Set
Human Physiology Body Water and Osmosis
Human Phys flashcards for exam 1