Hemodynamics Flashcards
What is the flow equation?
Q=A (v)
What type of flow does the below describe?
Q= Q1= Q2= Q3…..
Flow in a series….it is constant
What type of flow does the below describe?
Q= Q1+ Q2+ Q3…..
Flow in parallel…it is additive
What is blood flow through an INDIVIDUAL organ equivalent to?
It is equivalent to flow through a SERIES
Can there be differences in reistance in different organs?
Yes, there can be dramatic differences
What is the total peripheral resistance (TPR)?
It is the overall resistance to flow throughout the circulation
How are organs arranged in terms of flow?
In a parallel network (note however, the flow through an individual organ is a series flow)
How does the resistance of each organ contribute to the TPR?
additive, but in an inverse relationship
What do pressure differences between the aortic valve and the RA come from?
frictional losses from circulation
MAP=
CO x TPR
CO is approximately equal to what?
Q (resistance)
TRP=
P aorta - P r. atrium
_______________
CO
Resistance decreases in what condition and increases in what other condition?
Decreases= during exercise Increases= during hypertension
What is the critical parameter that characterizes flow?
The Reynolds Number
What does the Reynolds number take into account?
disruptive forces (numerator) and cohesive forces (denominator)
What is viscosity?
A measure of intermolecular attractions in the liquid
It determines the stepness of the velocity gradient
When does laminar flow break down?
When velocity reaches a critical point (exceeds the Reynolds number)…resistance increase
In laminar flow, what is flow proportional to?
Change in P
For the same Change in P, which has more flow….turbulent or laminar?
Laminar Flow
Which type of flow is silent and which flow generates a sound?
Silent= Laminar Sound= Turbulent
What are turbulent flow sounds called?
Auscultory sounds
What are murmurs?
audible sounds due to vibrations in heart or vessel walls
What is an “innocent” cyctolic murmur?
occurs when cardiac output increases during excercise which causes turbulent aortic flow during systole
What is the gravitational pressure equal to?
(density) (gravity) (height)
What is mean circulatory pressure?
the equilibrium pressure that would result throughout the cardiovascular systen if the heart stopped beating.
It ia 7 mm Hg
Fluids flow from ________ energy to ________ energy.
High energy to low energy
What causes static pressure? What causes dynamic pressure?
Static pressure is coposed of the applied or lateral pressure and force of gravity
Dynamic pressure is due to kinetic energy
If the energy is constant for blood flowing in a segment of a vessel what are two important conclusion?
1- As velocirt decreasesm dynamic pressure becomes a smaller fraction of the total pressure
2- As vessel radius narrows, the dynamic component increases significantly
What are forces parallel to blood flow?
Sheer and Strain
What creates sheer stress
Flowing blood on the endothelial wall directed along to long axis of the vessel
What is sheer stress proportional to?
The viscosity and the sheer rate (rate at which the axial velocity changes from the wall to the lumen) and the flow rate
What is sheer stress inversely proportional to?
cube of the vessel radius
In a blood vessel, which area has the minimal frictional retardation and maximal velocity?
the axial layer
Is sheer stress involved in endotheliam cell signalling and the development of atherosclerosis?
Yes
True or False:
Anything that changes the velocity will lead to stress and sheer
True
In constriction of an artery, what type of pressure decreases and what type of pressure increases?
Lateral pressure decreases and dynamic pressure increases.
This is because whenever blood velocity increases, a greater proportion of the blood pressure is converted from lateral into dynamic pressure
