A picture demonstrating blood pressure stages:
What is Haemodynamics?
Is the relationship between blood flow, blood pressure and resistance to flow
What does Force refer to?
Cardiac contraction
What does work refer to?
Isovolumetric contraction and ejection
What does pressure refer to?
Difference of pressure between the aorta to veins
What does compliance refer to?
Arterial stretch
What does resistance refer to?
Arterioles
What does Flow velocity refer to?
Slowing down blood flow in capillaries
What does CVS stand for in haemodynamics?
Cardiovascular System
Reduced blood flow to one area in the CVS will increase what?
Pressure upstream and alters flow to other areas
Where is the majority of blood kept? (what system)
The venous system
What is a characteristic of the venous system?
A low pressure system
The reservoir of venous blood can be used to increase what? What Law refers to this?
-Increase Cardiac Input
-Starlings Law
What is the Pulmonary circuit responsible for?
Is responsible for carrying blood between the heart and the lungs
What is the Systemic circuit responsible for?
Is responsible for carrying blood between the heart and the rest of the body's tissues and organs
Picture demonstrating pressure changes and drops in the pulmonary and systemic circuits:
What does Darcy's Law describe?
The flow of fluid through a porous medium, such as blood flowing through blood vessels
What does the Bernoulli's Principle state?
In a flowing fluid, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy
What is an equation for Flow that involves R (resistance)?
Flow = P1-P2/R
What is an equation for Flow that involves TPR (Total Peripheral Resistance)?
Flow = Pa-CVP/TPR
What is an equation for Flow that involves kinetics?
Flow = Pressure (P) + Kinetic (pV^2/2) + Potential (pgh)
What is the definition of blood flow?
Volume of blood flowing in a given time (ml/min)
What is the definition of perfusion?
Blood flow per given mass of tissue (ml/min/g)
What is the definition of the Velocity of blood flow?
Blood flow (cm/s) affected by the cross-sectional area throughwhich the blood flows, so flow may remain the same but velocity changes if there has been a change in cross-sectional area
What is the equation for volume flow (Q)?
Volume Flow (Q) = Velocity (V) x Area (A)
What is the equation for velocity (V) that involves Flow?
Velocity (V) = Flow/Area
The greater the cross-sectional area...........
The slower the flow
Does the branching of arteries slow velocity?
Yes
Is the Velocity of blood flow in the aorta high or low?
High
Where is Laminar flow the most prevalent in? (4)
-Most arteries
-Arterioles
-Venules
-Veins
What are the characteristics of Laminar Flow? (5)
-Concentric shells
-Zero velocity at walls (molecular interactions)
-Maximum velocity at centre
-Moves RBCs towards centre
-Speeds up blood flow through narrow vessels
Where is Turbulent flow the most prevalent in? (3)
-Ventricles (mixing)-Aorta (peak flow)-Atheroma (bruits)
What are the characteristics of Turbulent Flow? (2)
-Blood does not flow linearly and smoothly in adjacent layers (whirlpools, eddies, vortices) due to increased pressure and velocity
-High resistance to flow
Where is Bolus flow the most prevalent in? (1)
-Capillaries
What are the characteristics of Bolus Flow? (2)
-RBCs have a larger diameter than diameter of capillaries, so move in single file
-Plasma columns are trapped between RBC Uniform velocity, little internal friction & very low resistance
What is Reynolds number? (2)
-A dimensionless quantity used in fluid dynamics to predict the flow characteristics of a fluid (such as blood) in a particular environment, such as a blood vessel
-It helps determine whether the flow is laminar or turbulent at a given point
What is the equation for Reynolds number?
Re = pVD/μ
When does Turbulence occur?
When Reynold’s number exceeds a critical value (>2000)
What are some physical manifestations of turbulence?
-Bruits
-Ejection murmur
-Increased blood velocity
What is pulse pressure?
Is the difference between the systolic and diastolic blood pressure readings
-It is a measure of the force exerted by the blood as it is ejected from the heart during systole and the pressure in the arteries when the heart is at rest during diastole
What is pulse pressure, a measure of?
It is a measure of the force exerted by the blood as it is ejected from the heart during systole and the pressure in the arteries when the heart is at rest during diastole
FILL IN THE BLANKS:
Arterioles are the ___________ ___________ under sympathetic control
Resistance Vessels
Arterial blood pressure involves interactions between four key relationships, which are?
-Systolic pressure
-Diastolic pressure
-Pulse pressure
-Mean blood pressure
What is systolic pressure? (short answer)
Pressure when relaxing
What is diastolic pressure? (short answer)
Pressure when relaxing
What is pulse pressure? (short answer)
Difference between diastolic and systolic pressure
What is mean blood pressure? (short answer)
Average pressure
During left ventricular systole, how much % of stroke volume is stored in the aorta and arteries as these structures expand. The energy will be stored in stretched elastin.
60-80%
What happens during left ventricular diastole?
-Energy is returned to the blood as the walls of the aorta and arteries contract.-This sustains diastolic blood pressure and blood flow when heart is relaxed
What does Pulse pressure tell you about?
-Stroke volume and-Arterial compliance (stretchiness)
What is an equation for pulse pressure that involves compliance?
Pulse pressure = Stroke Volume/Compliance
If compliance is low, is pulse pressure also low?
NO pulse pressure is high when compliance is low
During exercise greater stretch of the arteries as more blood is ejected.
This causes what?
Causes less compliance and less recoil and the difference between systole and diastole increases i.e. pulse pressure increases
Compare exercise against rest:
Rest v Exercise• Greater stroke volume• Greater stretch of arteries• Less compliant• Relatively greater systolic pressure
How does decreased arterial compliance impact stroke volume?
Stroke volume now increases systolic and pulse pressure disproportionally
Elderly people have stiffer arteries, this results in decreased....?
Compliance
Pulse pressure becomes more noticable where on the arterial tree? And why?
-Further down the arterial tree
-Because vessels become less compliant
What is the complicated way to work out mean blood pressure (BP)?
Mean BP = integrate area under curve
What is the simpler formula for Mean BP?
Mean BP = diastolic pressure + 1/3 (pulse pressure)
What factors controls mean blood pressure?
• Age• Disease• Distance along arterial tree• Blood volume – affects SV, CO• Exercise – increased SV, CO• Emotion - stress, anger, fear, apprehension, pain• Wake/sleep - decreases BP 80/50 mmHg