1,2- Overview of Circulation and Hemodynamics Flashcards
arteries
for high pressure to transport to organs
arterioles
for controls and distribution of flow
capillaries
to exchange nutrients, electrolytes, hormones, etc.
have the largest overall cross sectional area, in parallel with one another. blood moves the slowest here so you have time for exchange of nutrients/O2 and CO2
venules
to collect blood from the capillaries
veins
to transport of blood back to heart
Order of systemic circulation
arteries -> arterioles -> capillaries -> venules -> veins
are pulmonary and systemic circulation in series or parallel?
series but within each are parallel elements so blood is distributed to various vascular beds independently depending on what the tissues needs are. also means that disruption in blood supply to one part of circulation doesnt mean it will disrupt everywhere
is arterial or venous pressure higher?
arterial but most of the blood is in the veins (venous side is more compliant)
100ml of blood is what makes the arterial pressure
explain the pulsatile nature of the heart
pressure is most pulsatile near the “pulsing” heart. you have the largest pressure drop at the arterioles. Pressure overall drops as blood moves from arterial to venous sides of circulation and pressure becomes less pulsatile.
bloodflow in an individual vessel segment is determined by
inflow-outflow pressure
relationship between pressure/flow/resistance
change in pressure = flow x resistance
flow is always in the direction from high to low pressure
blood pressure
bp = force exerted by blood / area of vessel wall
Conductance
measure of blood flow through a vessel for a given pressure difference. Simply the inverse of resistance
1/Resistance
C~d^4 (varies in proportion of the 4th power of diameter)
Poiseuille’s Law
F= (deltaP) (Pi) r^4/ 8 (viscosity)(length)
Note: vessel radius plays greatest role in determining rate of blood flow through a vessel
Ohms law with respect to the heart
F = (deltaP) / R
laminar flow
steady state flow streamlines
hematocrit
% of cells in blood, pressure must go up to surpass viscosity factor
normal men ~42%
normal women ~38%
anemia < normal
polycythemia > normal
Calculate resistance in series and parallel
series-> add them and the total is greater than the largest
parallel-> add 1/each R together and the total is less than the smallest
systolic vs. diastolic pressure
systolic pressure- each time the heart beats it ejects blood which increases arterial bp to peak
diastolic pressure- as vessels empty, blood moves from arteries to veins the pressure falls
pulse pressure
systolic pressure - diastolic pressure
how to increase systolic pressure
goes up if vessels get stiffer and harder
how to increase diastolic pressure
goes up if you have an elevated HR
arterial pressure contours
- stroke volume ejected into arterial tree (how much blood is pumped out of heart)
- force of contraction/how hard heart is pumping (determines peak systole)
- heart rate determines time of diastolic runoff (longer time between beats the greater the runoff of the ejected volume into the venous circulation, and therefore the lower the diastolic pressure)
- arterial vascular resistance (a greater resistance reduces the runoff of blood into the veins before the next beat and therefore diastolic pressure is high)
what happens during aortic regurgitation
ejected stroke volume flows back inot the ventricle (regurgitation) during diastole; with an A-V shunt blood flows directly into the venous circulation. Both lower diastolic pressure.