APK 2105C Study Guide - Quiz Guide: Venae Cavae, Pressure Gradient, Blood Pressure

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Chapter 14 All Lectures
Lecture 1
Chapter 14, Lecture 1
Vessels & Blood Pressure
Stroke volume = blood flow from heart per cardiac cycle (heartbeat)
Cardiac output = blood flow leaving per minute
o How quickly heart is beating, how strong heart is beating
o CO = HR x SV
o Regulation is both intrinsic and extrinsic
Intrinsic = from within the organ
Extrinsic = from the nerve system
Physical laws of blood flow and BP
o Same laws that describe liquid flowing through pipes
o Flow = deltaP / R = (P1-P2)/R
Delta P = pressure gradient = change in pressure
R = resistance
Any factors that hinder blood flow
Flow is inversely proportional to resistance
Flow is directly proportional to pressure gradient
P1 = starting pressure, P2 = ending pressure
o How do you increase or decrease flow?
Increase P1 to increase flow
Decrease P2 to increase flow
Decrease R to increase flow
Inverse of above is true to decrease flow
Pressure gradients in the CV system
o Bulk flow = regardless of the medium (gas, liquid, air), the driving force for bulk
flow is a pressure gradientdirection of flow is always down gradient
High BP low BP
o Rate of flow depends on pressure DIFFERENCE, not absolute pressure
Without pressure gradientno driving force
o DeltaP for systemic blood flow = MAP CVP
Difference between blood flow from aorta (right after it leaves the heart)
and other end of system before it comes back into the heart
Aortic pressure = 85 mmHg (MAP) = P1
Driving force for blood flow through system
Very tightly regulated
Pressure gets lower as it gets close to capillaries
Vena cava pressure = 0 mmHg (dumping into RAcentral venous
pressure = CVP) = P2
CVP is actually 2-5 mmHg but is so lownegligible
o Pulmonary vs. systemic circuit flow
Same in pulmonary AND systemic
Pressure is maintained through
large arteries
o Falls off with smaller
arteries, arterioles
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Veins, vena cava have very low pressure
Pressure generated in pulmonary is much lower than in systemic
Have same P2 thoughstill 0 mmHg
RV is pumping pulmonary, LV is pumping systemic
LV walls are much thickerable to generate more force/pressure
Flow out of R side of heart is the same as L side of heart
o CO is same on both sides
o CO = blood flow out of the heart every minute
o Same pressure…how? Resistance is very different
Lecture 2
Chapter 14, Part 2
Vessels & Blood Pressure
Resistance in the CV system
o Resistance of individual vessels depends on
Physical dimensions of tube
Lots of branches in the “tubes” through the body
Properties of the fluid
Viscosity
o Factors impacting resistance
Vessel radius = NUMBER ONE factor in impacting resistance
Vasoconstriction
Vasodilation
Vessel length
Longer vessels = far more resistance
Not a factor in the body—vessels don’t just get longer instead in
periods of growth
Blood viscosity
Thicker blood = more resistance
Determined by cell/protein conc
Not normally factor in the body
o Poiseuille’s Law
Fluid flowing through a tube encounters resistance from the walls of the
tube and the fluid itself
Resistance = (8Ln)/(pi r^4)
L = length of tube
n = viscosity of fluid
r = internal radius
o r is to ^4
As r decreases, it impacts resistance to the ^4
very big impact
If radius is decreased by 1/2, resistance increases
16 fold
Biggest impact on resistance
L and n are directly proportional to resistance
o Total peripheral resistance (TPR) = combines resistances of all the vessels in the
network
Vasoconstriction and dilation ANYWHERE changes the TOTAL
resistance of the network of vessels
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Flow = pressure gradient / resistance
CO = MAP (mean arterial pressure) / TPR
May need to be rearranged
Refers to CO to a specific location/organ
Lecture 3
Chapter 14, Lecture 3
Vessels & Blood Pressure
Review of the vessels
o Lumen
o Endothelium
Only layer in capillaries
Allow for diffusion
o Smooth muscle
Veins have less smooth muscle than arteries
o Connective tissue
o Arterioles have highest ability to generate resistance against blood flo
o Arteries are both stiff and flexible
o Artery arteriole capillary venule vein
Arteries are both stiff (collagen) and flexible (elastic)
Have lots of smooth muscle in them
Very elasticgood for blood flow
Lots of collagen in walls of arteriesmore than in veins
o Collagen is very strongadd stiffness to artery walls
Vein has larger lumen
Blood vessels and pressure
o Blood vessels expand when pressure inside it increasecontracts when
pressure falls
Degree of distention depends on transmural pressure
Dependent on pressure inside and outside the vessel
o Ex: if pressure outside is high, won’t be able to expand as
much when pressure increases inside
o Elasticity acts to push back on pressure trying to expand
the vessel
More important in arteriesmore elastic
o Compliance = change in volume per unit change in transmural pressure
The ease with which a vessel expands
If walls are very stiff, generates lots of pressure inside (arteries)
Arteries have low complianceveins have higher
Compliance = change in volume / change in (pressure inside pressure
outside)
o Arteries = pressure reservoir
Low compliance from collagen, elasticity
Wall stores pressure and help maintain BP
Takes a lot of transmural pressure to get them to distend
o Arterial BP
Systolic BP (SBP) = max pressure in aorta occurs
Diastolic BP (DBP) = min pressure in the aorta occurs
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