1. DYNAMIC EQUILIBRIUM OF BODY FLUID
I NJOMAN WIDAJADNJA (FKIK-UNTAD) /
DENNY AGUSTININGSIH (FK-UGM)

2. BODY FLUIDS Main Functions: Other Functions:
Solvent
Transport
Other Functions:
Give shape and form to the cells
Regulate body temp.
Joint lubricant
Cushion body organs
Maintain peak performance

3. Body composition In average young adult male: % of body weight
18%
Protein, & related substances
15%
Fat 7%
Mineral
60%
Water

4. Factors affecting body fluids
Water intake & output
Age:
- infant: 73%
- elderly: 45%
Sex:
- adult male: 60%
- adult female: 40-50%
Body temperature
healthy adult can sweat 1 liter/hr for 2 hrs (5% of body wt without problem)
perspire (1000cc wet sheet)
Every degree F = 75 ml increase/day in fluid needs
Obesity
Climate
Habits
Level of physical activity

5. Body Fluid Compartments
Intracellular (ICF)‏
Extracellular (ECF)‏
Interstitial
Plasma
Figure 5-13: Body fluid compartments

6. Total Body Fluid by Compartment
Total Body Water

7. COMPOSITION OF BODY FLUIDS

8. Electrolytes in body fluids
Ions form when electrolytes dissolve and dissociate
4 general functions
Control osmosis of water between body fluid compartments
Help maintain the acid-base balance
Carry electrical current
Serve as cofactors

9. sodium pump ~ Na,K-ATPase: capillary wall plasma membrane
Normal Ions and electrolytes Composition of the Body Fluids.
sodium pump ~ Na,K-ATPase: Na K
capillary wall plasma membrane

10. ICF differs considerably from ECF
ECF most abundant cation is Na+, anion is Cl-
Sodium
Impulse transmission, muscle contraction, fluid and electrolyte balance
Chloride
Regulating osmotic pressure, forming HCl in gastric acid
Controlled indirectly by ADH and processes that affect renal reabsorption of sodium
ICF most abundant cation is K+, anion are proteins and phosphates (HPO42-)
Potassium
Resting membrane potential , action potentials of nerves and muscles
Maintain intracellular volume
Regulation of pH
Controlled by aldosterone
Na+ /K+ pumps play major role in keeping K+ high inside cells and Na+ high outside cell

11. HOMEOSTASIS Claude Bernard (1878): animals have 2 environtments
- milieu exteriur : physically surrounds the whole organism
- milieu interieur : surrounds the tissue and cells of the organism
organic liquid
homeostasis

12. Daily Water Gain and Loss

13. TRANSPORT OF BODY WATER AND SOLUTE
Osmotic pressure (concentrations of all solutes in a fluid compartment) is equivalent between ECF and ICF compartments
the solutes move from the lower op to the higher op

14. Osmosis
biopsych4e-fig jpg

15. Tonicity
In isotonic medium (isoosmotic concentrations on both sides of cell membrane) influx and efflux of water is equal. No netflux. Cells maintain volume (left).
In hypertonic medium (hyperosmotic concentration) there is a net efflux of water. Cells shrink (middle).
In hypotonic medium (hypoosmotic concentration) there is a net influx of water. Cells gain volume (right).

16. Osmolarity vs. tonicity
related, but different concepts.
they both compare the solute concentrations of two solutions separated by a membrane.
osmolarity takes into account the total concentration of penetrating solutes and non-penetrating solutes,
=jumlah partikel yg aktif secara osmotik(ion/molekul utuh)
tonicity takes into account the total concentration of only non-penetrating solutes.
= `sifat larutan` dan bagaimana larutan tsb mempengaruhi volume dlm sel dlm hal capaian ekuilibrium (tampak hanya air yg bergeser-geser )

17. Osmolarity vs. tonicity
Penetrating solutes can diffuse through the cell membrane, causing momentary changes in cell volume as the solutes "pull" water molecules with them.
Non-penetrating solutes cannot cross the cell membrane, and therefore osmosis of water must occur for the solutions to reach equilibrium.

18. Osmolarity vs. tonicity
A solution can be both hyperosmotic and isotonic.
For example, the intracellular fluid and extracellular can be hyperosmotic, but isotonic –
if the total concentration of solutes in one compartment is different from that of the other, but one of the ions can cross the membrane, drawing water with it and thus causing no net change in solution volume.

19. Membandingkan Osmolaritas
Larutan A =
Glukosa 1 Osm
Larutan B =
Glukosa 2 Osm
Larutan C =
Na Cl 1 Osm
A hiposmotik
terhadap B
B hiperosmotik
terhadap A
C isosmotik
terhadap A
A isosmotik
terhadap C
C hiperosmotik
terhadap B

20. Sel tidak berubah ukuran
Tonisitas Larutan
Larutan
Perilaku Sel di
Dalam Larutan
Penjelasan Sifat
Larutan Terhadap
Sel A
Sel membengkak
Larutan A hipotonik B
Sel tidak berubah ukuran
Larutan B isotonik C
Sel mengkerut
Larutan C hipertonik

21. Hubungan Osmolaritas dan Tonisitas
Hiposmotik
Isosmotik
Hiperosmotik
Hipotonik
Isotonik
Hipertonik

22. What cellular tools are available to counteract swelling or shrinking?
Rapid: opening of channels, activation of transporters
Slower: accumulation or disposition of intracellular organic osmolytes

23. Overview of Movement Across Membranes
Energy requirements
Physical requirements
Figure 5-14: Map of the ways molecules move across cell membranes

24. Diffusion: Passive & down a concentration gradient
Stops at equilibrium
Rate factors: membrane, temperature, distance, & size
Figure 5-16: Fick’s law of diffusion

25. PATHOPHYSIOLOGICAL CHANGES IN EXTRACELLULAR FLUID VOLUME
Volume Contraction
Isotonic
Hypertonic
Hypotonic
Osmolality
ECF
ICF
ECF
ICF
ECF
ICF
Volume Expansion
Isotonic
Hypertonic
Hypotonic
Osmolality
ECF
ICF
ECF
ICF
ECF
ICF
From H. Valtin

28. CONTROL OF WATER INTAKE
Primarily by THIRST
Stimuli:
1) Increased Osmolality
2) Decreased Arterial Pressure
3) Decreased Blood Volume
4) Angiotensin II

30. Two Kinds of Thirst
biopsych4e-fig jpg

31. Osmotic homeostasis
Changes in the osmolality of plasma lead to AVP secretion at a much lower threshold than they lead to thirst
Very small increases in AVP lead to very large changes in urine volume
Thus – the kidney is the first line of defense against cellular dehydration

33. AVP acts on V2 receptors (cAMP) in the kidney
Osmotic homeostasis
The initial response to cellular dehydration is release of arginine vasopressin (AVP) – the antidiuretic hormone
AVP is synthesized in the supraoptic n. and paraventricular n. of the hypothalamus and transported along axons to the posterior pituitary.
AVP is stored in secretory granules in posterior pituitary until an increase in osmolality of body fluids initiates its secretion into the blood
AVP acts on V2 receptors (cAMP) in the kidney
to increase water permeability by inserting
aquaporin channels into cell membranes
Water moves out of the distal convoluted
tubule of the kidney by osmosis through
these channels – decreasing osmolality
There is also an increased water
reabsorption by the kidney and
decrease in urine flow

36. Hypovolemia triggers not only thirst, but also salt appetite
Volume homeostasis
Hypovolemia triggers not only thirst, but also salt appetite
Blood volume is corrected only by replacing both water and salt
Drinking water alleviates thirst (by reducing plasma osmolality), but triggers salt appetite, whereas consuming salt triggers subsequent thirst (by increasing plasma osmolality)

38. Hormonal Regulation of Na+ and Cl-

39. Series of Events in Water Intoxication

40. Acid-base balance
Major homeostatic challenge is keeping H+ concentration (pH) of body fluids at appropriate level
3D shape of proteins sensitive to pH
Diets with large amounts of proteins produce more acids than bases which acidifies blood
Several mechanisms help maintain pH of arterial blood between 7.35 and 7.45
Buffer systems, exhalation of CO2, and kidney excretion of H+ / reabsorption of HCO3-

41. Buffer systems Act to quickly temporarily bind H+
Raise pH but do not remove H+
Most consist of weak acid and salt of that acid functioning as weak base
Major buffer systems: proteins, carbonic acid/bicarbonate, phosphates
Copyright 2009, John Wiley & Sons, Inc.

42. Buffer systems Protein buffer system
Most abundant buffer in ICF and blood plasma
Hemoglobin in RBCs
Albumin in blood plasma
Free carboxyl group acts like an acid by releasing H+
Free amino group acts as a base to combine with H+
Side chain groups on 7 of 20 amino acids also can buffer H+

43. Buffer Systems Carbonic acid / bicarbonate buffer system
Based on bicarbonate ion (HCO3-) acting as weak base and carbonic acid (H2CO3) acting as weak acid
HCO3- is a significant anion in both ICF and ECF
Because CO2 and H2O combine to form this buffer system cannot protect against pH changes due to respiratory problems in which there is an excess or shortage of CO2
Phosphate buffer system
Dihydrogen phosphate (H2PO4-) and monohydrogen phosphate (HPO42-)
Phosphates are major anions in ICF and minor ones in ECF
Important regulator of pH in cytosol

44. Exhalation of carbon dioxide
Increase in carbon dioxide in body fluids lowers pH of body fluids
Because H2CO3 can be eliminated by exhaling CO2 it is called a volatile acid
Changes in the rate and depth of breathing can alter pH of body fluids within minutes
Negative feedback loop

45. Regulation of blood pH by the respiratory system

46. Acid-base imbalances Normal pH range of arterial blood 7.35-7.45
Acidosis – blood pH below 7.35
Alkalosis – blood pH above 7.45
Major physiological effect of
Acidosis – depression of synaptic transmission in CNS
Alkalosis – overexcitability of CNS and peripheral nerves
Copyright 2009, John Wiley & Sons, Inc.

47. Changes in pH Acidosis – pH below 7.35 Alkalosis – pH above 7.45
CNS depression
Alkalosis – pH above 7.45
CNS hyerexcitability
Copyright 2009, John Wiley & Sons, Inc.

48. Some acid-base terminology
Acid: a proton donor
Base (alkali): a proton acceptor
Fixed (metabolic) acid: any acid except CO2
Metabolic acidosis/alkalosis – due to excess of any fixed acid or base
Respiratory acidosis/alkalosis – due to excess/deficit of CO2

49. Cytoplasmic pH is closely regulated
Generally, cells are more alkaline than would be expected if H+ was in electrochemical equilibrium (more than level 7 =7,35-7,45)
The Na+/H+ exchanger is an acid extruder
The Cl-/HCO3- exchanger is an acid loader
Both of these processes operate at some level all the time

50. An increase in cytoplasmic [H+] due to addition of fixed acid (intracellular metabolic acidosis) stimulates acid extrusion and inhibits acid loading  vice versa for intracellular metabolic alkalosis. Cells can usually defeat this kind of challenge, so long as there is not an extracellular pH disturbance as well.
If there is an extracellular pH disturbance, it will affect the responses of both acid loaders and acid extruders.