c1englezawater 2013 print.pdf

8/14/2019 C1EnglezaWater 2013 print.pdf

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Raluca PAPACOCEA MD PhD

Body water. March 2013

INTRODUCTION IN PHYSIOLOGY

PHYSIOLOGY=

Physis

= nature, living

been

+Logos = science

Thw

science

of natures

laws, of body functions

Introduced

by

J. Fernel, in

1542, as title

to

his

medical

textbook

Medicine

HISTORY

William Harvey -1628-

FIRST PHYSIOLOGY PAPER

Claude Bernarde

-1835-

the

internal

environment

concept

Pflugger

-1900

electrophysiology

Otto Frank, E. Starling, 1925blood

circulation

Cajal, Marinescu-1934, neurophysiology

Secenov, Pavlov-1904


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BODY WATER

WATER MOLECULE

PROPERTIES1. High polarity solubility = chemical reactivity2. High specific heat avoid hyperthermia3. High vaporisation heat - thermoregulation4.

High

thermal

conductivity

fast

tranfer

of the

heat; rich water tissues are not good insulators5. High surface tension - (-) role, prevent alveolarexpansion


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HIGH POLARITY

Water acts like a magnet and has 2 poles: positive andnegative (dipol). The positive end attracts the negativeions or the negative end of other polar molecules. Thenegative end is able to attract positive ions or thepositive end of other polar molecules.Water it is able to

dissolve many substances = universal solvent.Molecules that dissolve in water, such as carbohydrates,are named hydrophilic. In contrast, hydrophobicmolecule (compounds containing carbon and hydrogen)

cannot form hydrogen bonds with water. For example,fats, oils, alkans, paraffin, are hydrophobic molecules.


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High specifical heat Q = c x m x T

Specific heat is the amount of heat pergram, required to increase thetemperature by one degree Celsius. Therelationship between heat and

temperature change is expressed in theformula shown below where c is thespecific heat. where Q = heat added, c =specific heat and T= temperaturevariationThe specific heat of water is 1

calorie/gram C = 4.186 joule/gram C


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High heat of vaporization

(evaporation) is higher than any other common substance. Watermolecule absorbes

a lot of heat, playing a key role in

the body temperature regulation, especially in theprevention of the hyperthermia. is the energy required totransform a 1 gram of water into gas. Fluid water that

becomes water vapor absorbes heat in the processcalled evaporation. By heat absorbtion, evaporationcooles the surface exposed to this process. The amountof heat transfer depends on the evaporation rate, on the

air humidity and temperature. This property is alsoimportant for the body termoregulation. The sweatevaporation at the surface of body produces skincooling.


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High thermal conductivity

is the quantity of heat transmitted through a unitthickness in a direction normal to a surface ofunit area, due to a unit temperature gradient

(1C) under steady state conditions. Thermal

conductivity (heat transfer coefficient) of water is0,58 at 25C and provides the fast tranfer of the

heat; Tissues rich in water are not good

insulators. Fatty tissue - containing a very lowpercentage of water - is an efficient bodyinsulator


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High surface tension

is the property of a liquid surface that causes it to actlike a stretched elastic membrane. Surface tension iscaused by the attraction between the water's moleculesby intermolecular (cohesive) forces. It creates a drivingforce which diminishes the surface area and generates aspherical drops of liquid, (as the liquid tends to minimizeits surface area according to Laplace's law)In a sphericalorgan T = (P x R)/2,where T = tension and P= pressure.Surface tension is measured in dynes/cm, the force in

dynes required to break a film of 1 cm length.


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WATER BALANCE

Definition = the equilibrium betweenwater gain and water loss


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WATER BALANCE IN HUMAN

BODYGAIN (ml) LOSS (ml)

Drink

1500

Food 500Endogenous water 250(metabolism)

Urine 1500

Sweat 500Insensible water loss 150*Feces 100

2250 2250* Diffusion through skin and evaporation from the respiratory tract


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Water

distribution

1. Depends on age-

embrio97%

- foetus 85%- child 80%- adult 60%- elder 55%2. Depends on gender- male 60%

- female 50%

3. Depends on tissuea. Low water Enamel 0,2% dentine - 10%

bone

22%

Fat tissue 35%b. Rich

water

tissues

Muscle- 75% thyroid, kidney -80% brain 85%


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TOTAL BODY WATER Healthy adult, 70 kg 40 l water

60% from body weightIVF

= 5%

IF = 15%ICF = 40%ECF

20%


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THE 60 : 40 : 20 RULE60 TBW40 ICF20 ECF


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INTRACELLULAR COMPARTMENT

The most important quantity (40%) Exchanges with ECF only through IF

IC water

can

be

:

free

bound (matrix, gel) Sources: IFendogenous water Composition: K, phosphates, proteinates


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EXTRACELLULAR COMPARTMENT

Includes IVF+ IF+ transcellular fluid (1%)Transcellular fluid :- ICSF, endo/perilymph- aqueous humor and vitreous body- digestive secretions- pleural, pericardic, peritoneal, synovial fluidIn pathological cases (intestinal occlusion,pleuresy etc.) a new compartment appears:The TRANSCELLULAR COMPARTMENT


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ELECTROLYTES DISTRIBUTION IN

WATER COMPARTMENTS

ION (mEq/l)/ ECF ICFNa+ 140 14

K+ 4 140

Ca 2+ 5 0

Mg 2+ 2 40

Cl - 105 5HCO 3

- 24 10

Proteins 15 60


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Sodium (Na+)

is the main extracellular ion. It is involved in cellularexcitability because it is the generator of the actionpotential. It is also responsible for the electrical impulsetransmission. It participates in fluid and electrolytebalance by creating most of the osmotic pressure ofextracellular fluid. Daily average of Na+ intake exceedsthe bodys normal daily neccessities so kidneys eliminatethe suplimentary sodium. The Na+ level in the blood iscontrolled by hormones like aldosterone and atrial

natriuretic peptide (ANP). Aldosterone regulates sodiumreabsorption by stimulating a pump Na+ / K+


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Potassium (K+)

is the main positive ion from intracellularfluid. It generates the rest membranepotential, regulates thecellular excitability,

modulates muscle contraction, and blood

pH. The blood level of K+ is controlled

mainly by aldosterone (see above).


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Calcium (Ca+2)

is an extracellular ion, representing animportant component of bones and teeth.It is involved in blood clotting,

neurotransmitters release, maintenance ofmuscle tone, and excitability of nervousand muscle tissue. The plasma level of

calcium is regulated by parathyroidhormone and calcitonin. D vitamins control

Ca+2 absorbtion.


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EXCHANGES BETWEEN

COMPARTMENTS

DIFFUSION / FILTRATION / OSMOSISI. Diffusion = the main exchange

mechanism in microcirculation1. Simple D. passive particles transfer

from high to low concentration due to aCFicks

Law

Diffus C x A x Solub.flow

d x M

=


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Diffusion

Different substances diffuse across capillary walls bydifferent routes:Water, ions, and small molecules suchas glucose diffuse between adjacent endothelial cells(pores), or through fenestrated capillaries.Some ions(Na+, K+, Ca++, Cl-) diffuse through channels in cellmembranes. Large, water-soluble compounds must passthrough fenestrated capillaries.Lipids and lipid solublematerials (including O2 and CO2) diffuse throughendothelial cell membranes

by dissolving in lipid bilayer

of membrane. Plasma proteins cross the endotheliallining only in sinusoids, if pores are big enough.


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2. Facilitated

Diffusion

Needs a specifical carrier Is also passive Has a limited capacity Doesnt need energy

Diffusion - for fat substances - throughlipidic bilayer- for hydrosoluble substances through proteic channels, ionic channels

II FILTRATION


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II. FILTRATION Net filtration pressure NFP. = Profiltrant forces Antifiltrant forces NFP = (pc + i) ( c+ pi )

pc =30 mm Hg

c = 28 mm Hg

pHi

= -7 mm Hg

i = 5 mm Hg

pc =10 mm Hg

c = 28 mm Hg

pHi

= -7 mm Hg

i = 5 mm Hg

NET FILTRATION PRESURE (nfp)

ARTERIAL END : + 14 mm Hg

VENOUS END: -

6 mm Hg

p.ef. p.ef.


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ISOSFIGMIC POINT

FILTRATION

REABSORBTION

ISOSFIGMIC POINT


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APPLICATIONS OF CAPPILARY IFEXCHANGES (IVF) - (IF)Edemas = water in excess in the interstitial spaceMechanisms:pHc venous stasis flebitis, heart failure c

hypoproteinemia

lack

of proteins,

nephrotic syndrome, hepatic failure pHi lymph blockage neoplasma, filariosis

capillary

permeability

alergies, inflammations


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III.

OSMOSIS

MEDIUM 2 C2MEDIUM 1

C 1

C2 .C 1

PARTICLES

WATER

f f


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Water transfer from low concentration medium

into

high

concentration

medium

=

osmosisThe pressure applied to block the water transfer =osmotic pressure

().

does not depend on conc., but osmotic activeparticles numberosmotic active particles: ions, glucose, urea,proteins

Osmol = the exerted by 1 mol-gram ofunionizable

substance

mOsmolOSMOLALITY = OSMOLI / kg.water

OSMOLARITY = OSMOLI / liter

of solution


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A Molar Solution is an aqueous solution consisting of one mole of a substance plusenough water to make one Liter of solution.

A Molal Solution is an aqueous solution consisting of one mole of a substance plus 1kg of water (usually very close to 1 L water). The total volume may thus be more than 1 L


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Osmolarity

in Complex Solutions

As described under Units of Measure, the osmolarity of a simple solution is equal tothe molarity times the number of particles per molecule.Glucose has 1 particleNaCl has twoMgCl2 has three.


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b d i


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can be expressed in: -mosmoli/l- mm Hg: 1 mosmol = 19,3 mm Hg

normal = 300 mosm/l = 5450 mm HgThe fraction given by proteins = co =Coloid osmotic (oncotic) pressure = 28 mmHg

isotonic: = 300 mosm/lDepending on, hypertonic: >300 mosm/l, body fluids hypotonic :


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= c x R xT = osmotic pressure in mm Hgc = concentration gradientR = ideal gas constant

T= absolute temperature in degrees kelvin

vant Hoff Ecuation


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The cell volume changes depends ~osmolarityi x Vi = f x Vf

Vi = 100 c (erythrocite) i =285 mosm/lVf =88 c f =325 mosm/lDonnan membrane equilibrium (electrochemical) anions = cations


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Vesicular transport

is reserved for the specific transport oflarge molecules, usually proteins. Not allcapillaries display this mechanism.

Exocytosis

moves substance from the cell

interior to the extracellular space.

Endocytosis enables large particles andmacromolecules to enter the cell.


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WATER BALANCE REGULATION

1. WATER INTAKE REGULATION

2. WATER LOSS REGULATION


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REGULATION OF THE WATER

INTAKE Thirst is the driving force for water intake and

represents the physiological impulse to drinkwater.

A decrease in plasma volume of 10% and or an

increase in plasma osmolality of 1 to 2% resultsin stimulation of the hypothalamic thirst centre.

This causes a subjective sensation of thirst,which motivates the person to drink water.


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Thirst is stimulated by four

elements1. Hypovolemia: Low volume stimulates the lowpressure baroreceptors in the great veins and

right atrium2. Hypertonicity: Cellular dehydration acts via anosmoreceptor mechanism in the hypothalamus3. Hypotension: a decreasing in blood prerssurestimulates the high pressure baroreceptors in

carotid sinus and aorta

4. Angiotensin II: is synthesized in response torenal hypoxia. (hypotension, hemorrhage,anemia etc.)


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RENIN ANGIOTENSIN ALDOSTERONE

SYSTEM


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WATER BALANCE REGULATION

Is regulated by both, nervous and humoral mechanisms.A reflex mechanism has an anatomical substrate

represented by the reflex arch.

Each reflex arch consists of 5 elements:

ReceptorAfferent fibers

Nervous

center

Efferent fibers

Effector.


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RECEPTORS1. Osmoreceptors are located in hypothalamusand respond to changes in extracellular tonicity,

especially in Na+

2. Volume receptors (low pressure receptors)are located in the right atria and great veins3. Baroreceptors (high pressure receptors) arelocated in the carotid sinus and respond to

changes in mean arterial blood pressure.


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Nervous center

The central controller for water balance isthe hypothalamus. The osmoreceptors arelocated in the area known as the AV3V

(anteroventral 3rd ventricle).

Lesions in the AV3V region in rats causeacute adipsia (they do not drink water).


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2. WATER LOSS REGULATION

1. Sweating -10 ml/h at rest2. Insensible loss (perspiration)2. Feces3. Diuresis


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HUMORAL REGULATION

ADH ALDOSTERONE ANF


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ADH

ADH = peptidic hormon synthetised in thehypothalamus (supraoptic andparaventricular nuclei) and transported to

the posterior pituitary.

In high doses ADH inducesvasoconstriction so it is also known asvasopressin.


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ADH exerts its physiological actions by

binding specific receptors.V1 receptors are located in the smooth muscle

layer of the blood vessels

they induce

vasoconstrictionV2 are located in the membrane of the

nephrocytes of the distal tubule and collecting

tubule from kidney where ADH stimulates waterreabsorbtion causing:

- urine volume decrease- urine concentration increase- blood volume increase-

blood concentration decrease.

G O


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ADH is stimulated by:- Hypovolemia (decrease of blood volume) V =5-10%- Hypertonicity (increase of osmotic pressure) = 1%,- pain, stress, emotions- morphin, nicotin, barbituricsADH is

inhibited

by:

- hypervolemia- Hypotonicity- alcohol

ADH REGULATION


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Aldosterone

= mineralocorticoid hormone produced byadrenal gland.

It preserves Na in the body by increasing theNa

reabsorbtion and K/H

excretion in

kidney.Cl follows Na and water follows NaCl (due to

osmosis)Aldosterone increases blood volume andblood pressure


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Aldosterone regulation

Aldosterone is stimulated by:

-

Hypovolemia

- Hypotonicity- the decreasing of the Na/K ratio- ACTH- angiotensin II, prostaglandin Pg E1, E2Aldosterone is inhibited by:-

Hypervolemia

- Hypertonicity- Pg F1-

Pg

F2

At i l N t i ti F t /(P tid )


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Atrial Natriuretic Factor /(Peptide )ANF /(ANP)

Is a cardiac hormone secreted by the atrial wall inresponse to high venous returnRoles:

1. it lowers blood volume and blood pressure,2. produces vasodilation3. inhibits aldosterone and ADH release4.

increases glomerular

filtration rate

5. increases diuresis, natriuresis6. antirenin activity.

DISORDERS OF WATER


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DISORDERS OF WATER

BALANCE1. Isotonic fluid : - excess EC hyperhidration- lack

EC dehydration

2. Hypertonic : - excess EC hyperhidrationfluid IC dehydration(NaCl)

-

lack

IC hyperhidration

EC dehydration

2. Hypotonic : - excess EC hyperhidrationfluid IC hyperhidration(pure water) - lack IC dehydrationEC dehydration


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STUDY QUESTIONS

1. Transcellular fluid includes:A. Pericardial fluidB. PlasmaC. LymphD. Synovial fluidE. Interstitial fluid


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Answers

A, D

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