Hemodynamics Flashcards
what can blood flow through an organ be considered (circuit)
blood flow through a series network
how is blood flow to different organs controlled in the absence of difference in arterial blood pressure?
differences in resistance within the organs dictates the difference
which vessels have the largest resistance? what implication does this have to the overall resistance of an organ?
arterioles
means that the overall resistance in an organ is determined by the resistance of the arterioles and therefore their radius
how is blood flow controlled in organs?
by varying the tension in the smooth muscles of the arterioles
what is the overall resistance to flow through the circulation called? what is the equation?
total peripheral resistance
1/TPR=1/R1+1/R2+1/R3…
what is the equation relating TPR to friction?
TPR=frictional losses/Cardiac output
what equation relates TPR to MAP (mean arterial pressure)
MAP=COxTPR
what can we assume the central venous pressure is during calculations?
zero
describe the relationship between flow and driving pressure?
it is linear and beginning at zero. the slope of each line equals 1/R
how can one change the flow vs pressure graph?
by changing he resistance by changing the pressure of the system and/or the cardiac output
what is the normal value of TPR at rest?
1.2 PRU
what is the reynolds number and what does it determine?
Re=disruptive forces/cohesive forces
describes when flow is turbulent or not
what values of reynolds number constitute which type of flow?
Re3000 is turbulent flow
what is viscosity and what does it determine?
measure of intermolecular attractions in the liquid and it determines the steepness of the velocity gradient
when does laminar flow break down? what happens at this point?
when the velocity reaches a critical point
the flow depends less on pressure gradient because the effective resistance increases
what is the breakdown of laminar flow called? which flow has less flow for the same change in pressure and what does this demonstrate?
turbulent flow
there is less flow in turbulent flow (loss of kinetic energy)