Concept of SteadyState Balance Please give examples of steadystate balance What happens when a dam is constructed in a river valley What happens to you as you eat and drink every day Concept of SteadyState Balance ID: 934356
Download Presentation The PPT/PDF document "Chapter 1 Physiology of Body Fluids" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Chapter 1Physiology of Body Fluids
Slide2Concept of Steady-State BalancePlease give examples of steady-state balance.
What happens when a dam is constructed in a river valley?
What happens to you as you eat and drink every day?
Slide3Concept of Steady-State BalancePlease give examples of steady-state balance.
What happens when a dam is constructed in a river valley?
What happens to you as you eat and drink every day?
In humans, what is required to maintain steady-state balance?
Slide4Concept of Steady-State BalancePlease give examples of steady-state balance.
What happens when a dam is constructed in a river valley?
What happens to you as you eat and drink every day?
In humans, what is required to maintain steady-state balance?
Set-point
Sensors
Effector organs
Sensitivity of the system
Slide5Concept of Steady-State Balance
Please give examples of steady-state balance.
What happens when a dam is constructed in a river valley?
What happens to you as you eat and drink every day?
In humans, what is required to maintain steady-state balance?
Set-point
Sensors
Effector organs
Sensitivity of the system
Input > output is positive balance
Input < output is negative balance
Slide6Properties of solutions: Concentration
Concentration
The amount of a substance (weight) in a specified volume of solution
grams/Liter, mg /Liter, grams/100ml (dL or %), mg/100ml or dL, (other volumes must be declared)
The amount of a substance (moles) in a specified volume of solution
moles/Liter, millimoles/Liter, (other volumes must be declared)
Molarity
Glucose (180), Na (23), Cl (35.4), NaCl (58.4)
Avogadro’s number = 6.022 x 10
23
Example: 1 gram of glucose in 1 liter = = 0.0056 mol/L or 5.6 mmol/L
Slide7Properties of solutions: Content, EquivalentsContent
Amount of substance in specified volume
Amount = concentration x volume
Content of Na in ECV of 70 kg person = 140 mmol/L x 14 L = 1960 mmol
Content of Na + K in TBW of 70 kg person = 140 mmol/L x 42 L = 5880 mmol
Equivalents vs Moles
Dissociation of salts in water
NaCl in water: Na
+
Cl
-
CaCl2 in water: Ca++ 2Cl- Glucose is not a salt
Slide8Properties of solutions: OsmosisOsmosis
Movement of water across cell (semi-permeable) membranes
Driving force is Osmotic pressure
Osmotic pressure depends number of solute particles in solution
1 mmol/L of solute (1
mOsm
/L) generates 19.3 mmHg
Slide9Properties of solutions: OsmosisOsmosis
Movement of water across cell (semi-permeable) membranes
Driving force is Osmotic pressure
Osmotic pressure depends number of solute particles in solution
1 mmol/L of solute (1
mOsm
/L) generates 19.3 mmHg
Slide10Osmolarity and OsmolalityOsmolarity
Number of solute particles per 1 L of solution
Osmolality
Number of solute particles per 1 kg of solvent
Measured by lab
In dilute solutions – very little difference
Slide11Moles, Equivalents, Osmoles
Slide12Tonicity (osmole inequality)
Tonicity of a solution - related to its effect on cell volume
In biology, different osmoles – different effects on cell volume
Isotonic solution – no change of cell volume
Hypotonic solution – cell volume increases (swells)
Hypertonic solution – cell volume decreases (shrinks)
Example: 300 mmol/L of sucrose vs 300 mmol/L of urea
Both 300
mOsm
/kg H
2
O – isosmotic (same osmolality)Sucrose does not cross cell membrane – membrane impermeableEffective osmoleUrea crosses cell membrane – membrane permeableIneffective osmole (most of the time)
Slide13Oncotic pressureOncotic pressure – osmolality of large molecules (proteins)
Large molecules (proteins: albumin, globulins) exert greater osmolality than predicted
Mechanism not entirely understood
Slide14Specific GravityDensity of substance or solution compared to density of water
Density = Weight/Volume
Density of Water = 1 kilogram/liter, 1 gram/ml
Urinometer (original method)
Archimedes’ principle
Urine dipstick
Human plasma SG 1.008 -1.010
Dilute SG < 1.008
Concentrated SG > 1.020
Slide15Volumes of body fluid compartmentsTBW = 0.6 x body weight
ICF = 0.4 x body weight
ECF = 0.2 x body weight
Plasma = ¼ of ECF
Interstitial = ¾ of ECF
70 kg
Slide16Composition of body fluid compartments
ECF
ICF
Slide17Estimating plasma osmolality
Plasma vs Serum
Shortcuts – app not needed
[glucose]/20
[BUN]/3
Slide18Fluid exchange between compartments:Capillary fluid exchange
Starling forces
K
f
filtration coefficient
P
c
hydrostatic pressure in capillary
P
i
hydrostatic pressure of interstitial fluid
σ reflection coefficientπc oncotic pressure in capillaryπi oncotic pressure of interstitial fluidPre- & post- capillary sphincters
Slide19Fluid exchange between compartments:Cellular fluid exchange
Osmotic pressure between ECF & ICF drives water movement
Water across cell membranes through aquaporins
Clinical implications
Addition of isotonic saline to ECF
Isotonic saline (0.9% NaCl) contains 154 mmol NaCl
Ideal osmolality versus real osmolality
Addition of hypotonic saline to ECF
Hypotonic saline (0.45% NaCl)
Change in ECFV and ICFV after infusion of 1 liter
Addition of hypertonic saline to ECF
Hypertonic saline (3% NaCl) Molarity & osmolality?
Slide20Intravenous solutions