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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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Raluca PAPACOCEA MD PhD
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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