Ch 34: Control of Body Fluid Osmolality and Volume Ch 2 : Homeostasis of Body Fluids Fluid and Electrolyte Balance Fluid and Electrolyte Balance Fluid and Electrolyte Balance Fluid and Electrolyte Balance Myoung Kyu Park MD. PhD. Department of Physiology Sungkyunkwan University School of Medicine
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Ch 34: Control of Body Fluid Osmolality and VolumeCh 2 : Homeostasis of Body Fluids
Fluid and Electrolyte BalanceFluid and Electrolyte BalanceFluid and Electrolyte BalanceFluid and Electrolyte Balance
Myoung Kyu Park MD. PhD.Department of PhysiologySungkyunkwan University School of Medicine
Fluid and Electrolyte BalanceFluid and Electrolyte Balanceu d a d ect o yte a a ceu d a d ect o yte a a ce1. Distribution and measurement of body fluid compartmentsy p2. Compartmental fluid balance and compositions3. Systemic fluid balance : water intake & output4 Regulation mechanism of extracellular fluid volume4. Regulation mechanism of extracellular fluid volume5. Electrolytes balance
Body FluidBody FluidBody FluidBody FluidYoung men Young WomenYoung men Young Women
60% of body weight60% of body weight
50% of body weight50% of body weight
cf. water content ; fat tissue (10%), other tissues (70-75%)
Body Fluid CompartmentsBody Fluid Compartments70 kg man
Measurement of body fluid compartmentsMeasurement of body fluid compartments
Camount Substance Methods
TBW Tritiated water and D2O
V =amount
ECF sulfate, inulin, manitol
Plasma radioiodinated serum albumin, Evans blue
I t titi l ECF l l lV = concentration
Interstitial ECF vol – plasma vol
ICF TBW – ECF vol
Electrolyte Composition of the Body FluidsElectrolyte Composition of the Body FluidsElectrolyte Composition of the Body FluidsElectrolyte Composition of the Body Fluids
Disorders of Fluid BalanceDisorders of Fluid BalanceDisorders of Fluid BalanceDisorders of Fluid BalanceEtiology : liver, cardiovascular or renal disease, hormonal imbalance, or accidents
plasma-to-interstitial shift / plasma-to-transcellular space shift
Accumulation of fluid in interstices or connective tissues or transcellular spacesdue to increased hydrostatic pressure or decreased osmotic pressure (third space)
Control of Secretion of Antidiuretic Hormone (ADH)
Osmolality Volume
set pointset point
• Continuous control of ADH level over the set point (278mOsm) and under the 10%• Continuous control of ADH level over the set point (278mOsm) and under the -10% change in circulating blood volume
• Osmolarity and effective circulating blood volume work together and reinforce each other
Cellular mechanisms of ADH action
1. Insertion2. Expression
AQP2AQP2
Water AbsorptionWater AbsorptionADH
Diabetes insipidus – ADH deficiency (nephrogenic or neurogenic)20 L/day urine
Systemic responses to changes in blood osmolarity and volume
4. Atrial Natriuretic Peptide (ANP)
ANP t i•ANP - atrium•BNP - ventricle•Urodilantin - kidney
BNP / urodilantin
vasodilation
Feedback Control of Effective Circulating Volume
Na+ ion
• determines ECF volume
• generates electrical activities
• supplies energy for cellular transport
Na+
Na+ Transport GFR = 180 L/day, PNa+ = 142 mM Filtered Load = 25,500 mmole/day (1.5kg) Diet 120 mmole/day
ADH
Paracellular pathway
Transcellular pathway
Regulation of Na+ Transport
100
33
8
3
0.4
cortex
medulla
67%
25%
5 %
3 %
Na/K/2Cl transporter
Na cotransporter
Na/H exchanger
Solvent drag
Na channels
Na-Cl transporter
Na channels
1. Glomerulotubular balance
2. Aldosterone
3. Sympathetic nerves
1. Decrease RBF & GFR
2. Release renin
3. Stimulate tubular Na+ reabsorption (activates NHE3 & Na pump)
4. Arginine vasopression –ADH
5. Atrial Natriuertic Hormone
1. increase RBF & GFR
2. inhibit Na reabsorption in
the medulla
6. PG, bradykinin, & dopamine
inhibit Na+ reabsorption
1
2 3
4
5
5
4
inhibition
stimulation
H2O channels
Sodium Balancemajor factor determining ECF Vol.
Sodium in diet100 - 300 mEq/dayINPUT
Extracellular fluid
95%small
Gastrointestinallosses (diarrheavomiting)
Skin (sweat,burns,hemorrhage)
KidneysOUTPUT
vomiting)hemorrhage)
positive Na+ balance ECF vol. generalized edema
High intake hypertension
Renal Responses to Na+ intakewater intake ECF Wt gain