Systemic Circulation and Hemodynamics - Dr. Rogers Flashcards
Arteries with P
stress volume : high flow and pressure = BP
Arterioles
moderate P, SM walls
change resistance of blood
Capillaries
LARGE CROSS SECTION area, exchange site
Veins
Low P, large V, contract to move blood to arterial side = increase BP
greatest cross section area
capillaries
greatest blood V
Veins
blood flow =
Q= Pressure gradient (delta P)/Resistance (R)
Poiseullies law
resistance through tube calculation
R =
(8nl)/ (pi r^4)
n = viscosity
r= radius
l = length
if P stays the same how does R decrease
increase r of tube
+ increase flow rate to keep P the same
How to find viscosity
Hematocrit = (RBC: plasma) ratio increased hematocrit (high RBC) ----> lower BF
R of 8 tubes in series
you add the R for each = TOTAL R
*increases total R
R of 8 tubes in parallel
this lowers the TOTAL R
* capillaries are like this
another thing Q = to
over all heart function
Q= CO = (A P - V P) / TPR
greatest control of BF
TPR in arterioles
what increases and decreases TPR
Increase : increase sympathetic N to arterioles = vasoconstriction
Decrease : decrease sympatetic N to arterioles = vasodilation
how to calculate V of blood in BVs
V = Q/CSA
CSA: cross sectional area of vessle
highest and lowest V is found
highest : As
lowest : capillaries
3 things that make BF more likely to be turbulent
- high V
- large CSA
- low Viscosity
what is Reynolds Number
N= pdv/n
p - density
d- diameter
*if N > 2000 = laminar –> TURBULENT transition
what does turbulence cause
bruits sounds + lesions = arteriosclerosis
compliance
delta V/ delta P
* shows vascular capacitance
highest compliance
lowest complience
highest : veins
lowest : arteries
what condition can cause decrease in compliance
arterosclerosis, causes artery to be unable to distend (systole) and recoil (diastole) as much
reason Veins have compliance and what can this lead to is not functioning right
they have SM flexible walls
if the SM constrict (decrease v, same P) = lowers compliance = more blood pushes to arteries
= INCREASE BP
where is the biggest pressure drop in the circulation
arterioles
before the largest P drop in the circulation, what keeps the P high
Aorta, Large As, Small As all have high P due to Aorta having so much pulsatile action
Lowest BP
Highest BP
DIASTOLE : 80mmHg
SYSTOLE : 120mmHg
Pulse Pressure
SBP-DBP = 40mmHg
proportional to SV
How to calculate the Mean Arterial Pressure (MAP)
1/3 (SBP) + 2/3(DBP)
(DBP) + 1/3(pulse Pressure)
80-40/3 = 93.3mmHg
Dichroctic Notch
when aortic valve closes
compliance in the practical setting
SV/ Pulse Pressure
compliance and Pulse Pressure relationship
as compliance increases the pulse pressure decreases
increases R on compliance
decrease in R, lowers P, which increases Compliance
what happens in Arteriosclerosis
increase SPB, PP, and MAP
STAYS SAME : DBP