2The Body as an Open System l“Open System”. The body exchangesmaterial and energy with itssurroundings.
3Water BalanceWater is the solvent of life. Undoubtedly, water is more important than any other single compound to life. It is involved in several body function.Function of water1. Water provides the aqueous medium to the organism which is essential for the various biochemical reactions to occur.2. Water directly participates as a reactant in several metabolic reaction.3. It serves as a vehicle for transport of solutes.4. Water is closely associated with the regulation of body temperature.
9Solutes – dissolved particles Electrolytes – charged particlesthe compounds that when dissolved can carry an electrical currentCations – positively charged ionsNa+, K+ , Ca2+, H+Anions – negatively charged ionsCl-, HCO3- , PO43-# Cations must = # Anions for homeostatsis to exist in each fluid compartmentNon-electrolytes - UnchargedProteins, urea, glucose, O2, CO2
10Electrochemical Equivalence The concentration of electrolytes are expressed as milliequivalents / liter (mEq/l) rather than milligrams.Equivalent (Eq/L) = moles x valenceMonovalent Ions (Na+, K+, Cl-):1 milliequivalent (mEq/L) = 1 millimoleDivalent Ions (Ca2+, Mg2+, and HPO42-)1 milliequivalent = 0.5 millimole2020
12 Compartmental concentration (mEq/L) Table ELECTROLYTE COMPOSITION OF BOOD FLUIDS Compartmental concentration (mEq/L)Plasma Interstitial fluid Intracellular fluidPositive ion NaKCa MgTotalNegative ion Cl HCO3HPO42SO42Organic acid —Protein(Pr )Total
13Electrolyte composition of body fluids Electrolytes are well distributed in the body fluids in order to maintain the osmotic equilibrium and water balance.There is marked difference in the concentration of electrolytes between the ECF and ICF.Na+ is the principal extracellular cation while K+ is the intraxcellular cation.This difference in the concentration is essential for the cell survival which is maintained by Na+-K+ ATPase.
16Movement of body fluids DiffusionFrom higher concentration →lower concentration.Osmotic pressureDrawing power of water (dependent on the number or molecules in solution)IsotonicHypotonicHypertonicWater: move from hypotonic → hypertonic solution.
18Regulation of electrolyte balance Electrolytes and water balance are regulated together and the kidney play a critical role.The regulation is mostly achieved through the hormones aldosterone, ADH (Antidiuretic hormone) and renin-angiotensin.
19Aldosterone mineralocorticoid, steroid hormone. produced by adrenal cortex, increase Na+ reabsorption at the expense of K+ and H+.retain Na+, lose K+
20Antidiuretic hormone (ADH) or vasopressina 9-amino acid peptide hormoneproduced by specialized nerve cells in the hypothalamus and transported in the bloodstream to the posterior pituitary gland.mainly released when the body is low on water, increases water reabsorption by renal tubules.
21Renin-angiotensin system(RAS) Renin: peptide hormone (340 aa), secreted by the kidney.Angiotensinogen: α2-globulin, produced constitutively and released into the circulation mainly by the liver.Angiotensinogen→AngiotensinⅠ→AngiotensinⅡangiotensin-converting enzymePAI-1: Plasminogen activator inhibitor-1, inhibits fibrinolysis
22Renin-angiotensin system (RAS) adrenal glandsretain Na+AngiotensinⅡ can stimulate the release of aldosterone.Renin-angiotensin system regulates blood pressure and water (fluid) balance.
23Dehydration Two types: Dehydration is condition characterized by water depletion in body. It may be due to insufficient intake or excessive water loss or both.Two types:1. due to loss of water alone.2. Due to deprivation of water and electrolytes.Causes of dehydration:1. Diarrhea2. Vomiting3. Excessive sweating4. Adrenocortical dysfunction5. Kidney disease6. Deficiency of ADH
24Characteristic feature of dehydration Features of dehydrationa) The volume of ECF decrease, electrolytes concentration and osmotic pressure increase.b) Water is drawn from the ICF, shrunken cells and disturbed metabolism.c) ADH secretion is increased.d) Plasma protein and blood urea concentration increased.e) Loss of electrolytes from the body (Na+, K+, etc.).
25Overhydration Clinical symptoms of sever dehydration Increased pulse rate, Low blood pressure, Sunken eyeballs, Decreased skin turgor, Lethargy, Confusion and comaTreatment: intake plenty of water, 5% glucose solution.OverhydrationOverhydration or water intoxication is caused by excessive retention of water in the body. It may be due to excess intake or large volumes of salt free fluids, renal failure, overproduction of ADH.Clinical syndromes: headache, lethargy and convulsions.Treatment: stop water intake, administration of hypertonic saline.
26Points Function of water Distribution of water: ICF and ECF Electrolyte composition of body fluidsRegulation of electrolyte balancealdosterone, ADH (Antidiuretic hormone) and renin-angiotensinDehydration and Overhydration