1) The human body is composed of approximately 60% water in adult males and 50-55% water in adult females. Total body water is about 40 liters, with two thirds located intracellularly and one third extracellularly. 2) Electrolytes such as sodium, potassium, calcium, and magnesium are important solutes that help regulate fluid balance and distribution between intracellular and extracellular compartments. They also play critical roles in nerve impulse transmission and muscle contraction. 3) The kidneys and sodium-potassium pump work to maintain normal electrolyte concentrations in the blood and body despite constant losses through urine, sweat, and other routes. Dehydration can occur if fluid and electrolyte losses are not replaced.

2. Body Water Content
• Infants: 73% or more water (low body fat,
low bone mass)
• Adult males: ~60% water
• Adult females: ~50-55% water (higher fat
content, less skeletal muscle mass)
• Water content declines to ~45% in old age

3. Distribution of Body Solids & Fluids
• Intracellular: Inside cells
• Extracellular: Outside of cells
• 2 Types:
o Interstitial: Between cells
o Intravascular: Within blood
vessels

4. Fluid Compartments
• Total body water = 40 L
1. Intracellular fluid (ICF) compartment: 2/3 or 25 L in
cells
2. Extracellular fluid (ECF) compartment: 1/3 or 15 L
• Intravascular (Blood): 3 L
• Interstitial fluid (IF): 12 L in spaces between cells
• Other ECF: lymph, CSF, humors of the eye, synovial
fluid, serous fluid, and gastrointestinal secretions

5. Figure 26.1
Total body water
Volume = 40 L
60% body weight Extracellular fluid (ECF)
Volume = 15 L
20% body weight
Intracellular fluid (ICF)
Volume = 25 L
40% body weight
Interstitial fluid (IF)
Volume = 12 L
80% of ECF

6. Composition of Body Fluids
• Water: the universal solvent
• Solutes: nonelectrolytes and electrolytes
– Nonelectrolytes: most are organic
• Do not dissociate in water: e.g., glucose, lipids,
creatinine, and urea

7. Fluid Exchange in the Body
Processes in our body:
• Filtration
• Reabsorption
• Diffusion
• Osmosis

8. General barriers that separate intracellular
fluid, interstitial fluid, and blood plasma:
1. Plasma membrane
2. Blood vessel walls
3. Lymphatic vessels

9. Fluid Homeostasis
Fluid Balance
1. Water
2. Electrolytes

10. Figure 26.4
Feces 4%
Sweat 8%
Insensible losses
via skin and
lungs 28%
Urine 60%
2500 ml
Average output
per day
Average intake
per day
Beverages 60%
Foods 30%
Metabolism 10%
1500 ml
700 ml
200 ml
100 ml
1500 ml
750 ml
250 ml
1. Water

11. Dehydration
• Tired?
• Dizzy?
• Headaches?
You are dehydrated!
• Loss of body fluids  increased
concentration of solutes in the blood
and a rise in serum Na+ levels
• Fluid shifts out of cells into the
blood to restore balance
• Cells shrink from fluid loss and can
no longer function properly

12. 2. Electrolytes
• Electrolyte is a "medical/scientific" term for salts, specifically
ions.
• The term electrolyte means that this ion is electrically-charged
and moves to either a negative or positive electrode:
– ions that move to the cathode (cations) are positively
charged
– ions that move to the anode (anions) are negatively charged
• For example, your body fluids -- blood, plasma, interstitial fluid
(fluid between cells) -- are like seawater and have a high
concentration of sodium chloride (table salt, or NaCl). The
electrolytes in sodium chloride are:
– sodium ion (Na+) - cation
– chloride ion (Cl-) - anion

13. Electrolytes
• sodium (Na+)
• potassium (K+)
• calcium (Ca2+)
• magnesium (Mg2+)
• chloride (Cl-)
• phosphate (PO4
2-)
• bicarbonate (HCO3
-)
• sulfate (SO4
2-)

14. • Electrolytes are important because they are what your cells
(especially nerve, heart, muscle) use to maintain voltages
across their cell membranes and to carry electrical impulses
(nerve impulses, muscle contractions) across themselves and
to other cells.
• Your kidneys work to keep the electrolyte concentrations in
your blood constant despite changes in your body.
• For example, when you exercise heavily, you lose electrolytes
in your sweat, particularly sodium and potassium.
• These electrolytes must be replaced to keep the electrolyte
concentrations of your body fluids constant.
• So, many sports drinks have sodium chloride or potassium
chloride added to them.
– They also have sugar and flavorings to provide your body
with extra energy and to make the drink taste better.

15. Electrolytes
Hype???
• water, sucrose syrup, glucose-
fructose syrup, citric acid, natural
and artificial flavors, salt, sodium
citrate, monopotassium
phosphate, ester gum, sucrose
acetate isobutyrate, red 40, blue 1
• Per 8 fl oz
Total fat 0g
Sodium 110mg
Potassium 30mg
Total carbs 14g
Sugars 14g
Calories 50
• water, dextrose, potassium
citrate, sodium chloride and
sodium citrate. Nonmedicinal
ingredients: FD&C Blue #1 and
Red #40 (grape flavor) and
FD&C Red #40 (bubblegum
flavor).
• Per 8 fl oz
Sodium 10.6 mg
Potassium 4.7mg
Chloride 8.3 mg
Dextrose 5.9g
Calories 24

16. Electrolyte and protein anion concentrations in
plasma, interstitial fluid, & intercellular fluid

17. Sodium
• Major extracellular cation
• Attracts fluid and helps preserve fluid volume
• Combines with chloride and bicarbonate to help regulate
acid-base balance
• Should not exceed 2000mg/day

18. Potassium
• Major intracellular cation
• A low potassium level
can make muscles feel weak,
cramp, twitch, or even
become paralyzed, and
abnormal heart rhythms may
develop.
• Hypokalemia:
the level of potassium in
blood is too low
Potassium recommendation for males
and females is 4,700 mg per day.

19. Sodium-Potassium Pump
• Sodium-potassium pump
maintains normal
concentrations
• Pumps potassium into cells
• Pumps sodium out of cells
• Pump uses ATP, magnesium and
an enzyme to maintain sodium-
potassium concentrations
• Pump prevents cell swelling and
creates an electrical charge
allowing neuromuscular impulse
transmission
ATP is a high-energy
molecule found in every cell.
Its job is to store and supply
the cell with needed energy.
• Every cell uses ATP for
energy

20. Video:
• https://www.youtube.com/watch?v=_bPFKD
dWlCg

21. Magnesium
• Helps produce ATP
• Role in protein synthesis & carbohydrate metabolism
• Helps cardiovascular system function (vasodilation)
• Regulates muscle contractions
Males: 330-350 mg per
day
Females: 255-265 mg
per day.

22. Calcium
• 99% in bones, 1% in serum
and soft tissue (measured by
serum Ca++)
• Works with phosphorus to
form bones and teeth
• Role in cell membrane
permeability
• Affects cardiac muscle
contraction
• Participates in blood clotting
800 mg per day for both males and females.

23. Phosphorus
(phosphate (PO4
2-))
• The primary anion in the
intracellular fluid
• Crucial to cell membrane
integrity, muscle function,
neurologic function and
metabolism of carbs, fats
and protein
• Functions in ATP
formation, phagocytosis,
platelet function and
formation of bones and
teeth
(9 to 18 years): 1,250 mg/day

24. Chloride
• Major extracellular anion
• Sodium and chloride
maintain water balance
• Secreted in the stomach as
hydrochloric acid
• Aids carbon dioxide
transport in blood
Recommended intake ranges from 750 to 900 milligrams per day