Equations Flashcards
Osmotic pressure, π
π= RTC
Where R is the gas constant
T = temperature in K
C = conc in osml ^-1
Solute potential, Ψs
Ψs =-π
Water potential, Ψ
Ψ=Ψp + ψs
Einstein diffusion equation
t=x^2/2D
Where t is time
X is distance
D us diffusion coefficient, dependent on substance diffusing and medium
Darcy’s law of flow
Q = ΔP/R
Q is flow rate
R is resistance in tube
Nernst equation (for 20oC)
58/Z • log([ion]out/[ion]in)
Where Z is the charge of ion
Goldman-Hodgkin-Katz equation
E(K) = 58•log(Pk[K+]out/Pk[K+]in)
Where Pk is permeability of membrane to K+ ions. Can be expanded for multiple ions by adding to the log terms
Voltage along axons
V = V0•exp(-x/λ)
Where V0 is the initial voltage
X is the distance along the axon
λ is the length constant
λ=(Rm/Ra)^1/2 Rm= membrane resistance, Ra= axial resistance
Voltage in axon as a function of time
V(t) = Vmax(1-exp(-t/τ))
Where t is time
τ= time constant= Rm•Cm
Cm is the membrane capacitance
Work done
Force x distance
Force
Mass x acceleration
Power
Force x velocity
Blood pressure
= Cardiac output x vascular resistance
Main two ways of cardiovascular control
Cardiac output
= stroke volume x heart rate
Poiseuille’s law
Resistance α Lη/(r^4)
Where L= length of vessel
η= viscosity of blood
r= radius of vessel
Respiratory quotient
=CO2 eliminated/ O2 consumed
RQ carbohydrates=1
Fats = 0.7
Protein = 0.8
Dalton’s law
Total pressure is the sum of the partial pressures
Ptot = Po2 + Pn2 etc
Combined gas law
P1V1/T1 = P2V2/T2
Fick’s principles
V’gas = D•ΔP•SA/thickness
Where V’gas= rate of diffusion of gas across membrane
D= diffusion coefficient
SA= surface area of membrane
