Cardiovascular Physiology Flashcards
Receives greater amt of flow that exceeds its metabolic requirement
Remove wastes from it
Can withstand sevee reductions of blood flow
Lings, kidneys, GI, skin
Blood conditioning organ
Overall role of the Cardiovascular System
Homeostasis
Maintaining the constancy of internal environment
Blood flows solely to supply the metabolic needs
e.g. Brain
Metabolic organs
Everything in the cardiovascular system works to support this to maintain homeostasis
Microcirculation
Blood flows because of…
Pressure gradient
It will determine the flow
High pressure and low pressure
Microcirculatory diffusion of gases, nutrients and fluid is made possible by…
Adequate blood flow in and out of capillaries
How much fluid the heart puts out
Cardiac output
Volume of blood ejected by contraction
Stroke volume
Load imposed on the fluid before it goes out of the heart
Afterload
Load imposed on the fluid before it goes in
Determined by venous return
Preload
Which vessel regulates the flow of blood
‘Resistance vessels’
Constricts and contracts
Arterioles
Contricts
Affected by pressure gradient
Regulatory mechanism
Introduced fluid viscosity
What is it?
Isaac Newton
Highly viscous will flow slowly and vice versa
Laminar
Relationship of variables
Viscosity (n)?
Shear stress- stress the fluid encounters
Dyne/cm2
Shear rate- sec-1
If there is a lot of resistance on going forward, viscosity goes higher
The higher the shear stress, the higher the viscosity, the slower the rate (flow)
Windkessel model of the arterial system
Medieval tree is likened to a medieval fire cart
Established the relationship between flow, pressure gradient and tube dimensions
First used the mercury manometer to measure values of intra-vascular pressure
Intuitively deduced the presence of ‘resistance vessels’
Jean Leonard-Marie Pousseuille (1700s)
Relationship of variables
Poisseuille's equation: Q Volume flow per unit time K Constant D Internal diameter P1-P2 Pressure drop L Length
May be likened to Ohm’s Law (flow of electricity)
Resistance is inverse to the flow
The longer the length, the lesser the flow
The higher the viscosity, the lesser the flow
The greater the diameter, the greater the flow
The greater the pressure gradient, the greater the flow
What affects flow
Changing this results to an exponential change
Diameter of the vessel
Jean Leonard-Marie Pousseuille (1700s)
Other assumptions:
1 Liquid is homogenous and viscosity is same at all rates of shear
2 Liquid does not slip
3 Flow is laminar
4 Rate of flow is constant
5 Tube is long, compared to the region being studied
6 Tube is cylindrical and rigid
1 Hematocrit Percentage of RBC concentration in blood Measures blood viscosity 2 NOT TRUE 3 Parabolic shaped flow 4 FALSE 5 TRUE!!! When you are obese, you have longerp vessels, so the flow is slow! 6 Not rigid! Taper in the aorta. Elastic modulus along the aorta
So..good for a snapshot of the circulatory system, not really hemodynamics
Anomalous effect of blood or the Fahraeus-Lindqvist effect
Explain
Viscosity of blood decreases when tube size decreases
The RBCs accumulate in the middle part of the tube, leaving the other parts with liquid, so less viscous
Relationship of variables
Turbulence: Fluid density Velocity Diameter Viscosity
Fluid density - directly related
Fluid viscosity - inversely related
Breakdown of laminar flow
Turbulence
T or F
Blood flow is pulsatile, not steady
True
Young’s Modulus in the aorta
Elasticity of the aorta!!!
Introduced cardiac catheritization techniques
Cournand and Ranges
1941
Described the relationship between ventricular dimension and ventricular contraction
Otto Frank and Ernest Starling
1895, 1918
Measured intravascular pressure waves
Margo and Millar
1972
Used ultrasonic devices to measure flow velocity waveforms
Hartley and Cole
1974
T or F
Aortic valve closes earlier than pulmonic valve
True
