The basic principal of physiology
According to Lecture notes 2017 physiology and pre-test
simple diffusion: Fick equation
net flux = A *([s1]-[s2]) *D/d
A is area available for diffusion.
s1-s2 is concentration gradient of the substance.
d is distance for diffusion.
D is diffusion coefficient of the substance.
Mediate transport: lineweaver-burk equation
net flux = Vmax*[s]/(Km+[s])
The flow of water through membranes by osmosis.Described by the osmotic flow equation.
flow = k * L *(pai1 -pai2)
K is reflection coefficient.(varies between 1[impermeable] and 0[freely permeable])
L is hydraulic conductivity.
pai1 -pai2 is osmotic pressure difference across membrane.
pai is the pressure necessary to prevent solute migration.
The osmotic pressure: van’t hoff equation.
pai =RT(kIC)
R is ideal gas constant.
T is absolute temperature.
K is osmotic coefficient.
I is the number of the ions, dissociation of a molecule.
C is the molar concentration of solute.
KIC is the osmolarity of solution.Plasma osmolarity is estimated as 2[Na+]+[Glucose]/18+[BUN]/2.8.
when V changes.
pai inital *Vi =pai final *Vf
PH of plasma: Henderson - Hasselbalch equation
PH = PK1 + log([hco3-]/[dissolved co2])
Equilibrium potential (E) is calculated with Nernst equation
E ion = 61.5log(C out/C in)
E x+ =(60/z)log ([x+]out/[x+]in)
Dalton law :the total pressure of a gaseous mixture.such as atmosphere is equal to the sum of the partial pressure of the constituent gases.
Pgas =(Ptotal)(FIgas) = (Ptotal -Ph20)(FIgas)=(Ptotal -47mmhg)(%gas/100)
Pao2 = Pco2- (Paco2/R)
R is the respiratory gas exchange ratio.(Vco2/Vo2) which under normal circumstances, its value depends on metabolism and is equal to 0.8.
VE minute ventilation = Vt(tidal volume)*respiratory rate.(breaths/min)
Vd ,anatomical dead space, is estimated as 1ml/lb of body weight.
Vd/Vt =Paco2-Peco2/Paco2.
Thus alveolar ventilation = (Vt-Vd)*respiratory rate.
Paco2 =Vco2/Va
poseuille law
compliance is defined as Vchange/Pchange
airway resistance,R aw =Pchange/V=(Patm-Paw,cmh2o)/Flowrate,l/sec =8ln/pai r4.
l is length.n is viscosity.r is radius.
CO = HR*SV(stroke volume)
Laplace law
wall stress(T) = P(systolic pressure) *r(radius of the ventricle)/w(thickness of the ventriclar wall)
capillary fluid balance
depend on the balance between the hydrostatic(P) and the osmotic pressure (pai),and the permeability of capillary wall(Kf), starling law.
Filtration =Kf[(pai i+Pcap)-(Pi +pai cap)]
During an inflammatory response.Kf increases,plasma proteins decrease,pai cap decreases.
in the situation of kindney,the starling forces between the glomerular capillary and bowman capsules(BC),And the filtration is called GFR.
ideal gas situation equation
PV =NRT