Hemodynamics Flashcards
Describe the Basic principles of hemodynamics:
1) RATE of blood flow to tan organ or tissue is related to the needs of the organ or tissue (activity increases demand)
2) Cardiac output controlled by sum of individual tissue needs (Heart pumps out what returns to it via veins immediately)
3) Arterial Pressure regulation is independent of local blood flow or cardiac output control
- Nervous reflexes activated by pressure instantaneously regulate blood pressure
- Hormones work long- term to influence blood pressure through altering tone and blood volume
Describe the factors affecting Blood flow
Ohm’s Law: Flow = Pressure/resistant
- an INCREASE in resistant, DECREASES blood flow
POISEUILLE’s LAW (rigid tubes)
- FLOW = pressurecircumfrence/viscositylength
- ANOMALOUS VISCOSITY: as blood flow decreases, VISCOSITY INCREASES.
Describe the to types of Blood flow patterns
LAMINAR FLOW = organized into concentric layers (EFFICIENT)
- blood flows fastest at the inner layer (reduced friction)
- blood flows slowest at the edges due to friction with epithelial cells
TURBULENT FLOW = disorganized flow
- very inefficient - high energy cost to move blood
- Eddy currents of blood increase resistence
- NOISEY!!
- often when vessels branch, or bulging in a vessels
Define Korotkoff Sounds
-the sound of turbulent blood flow during a blood pressure check due to closing of the vessels.
Which vessels are more prone to turbulence
- LARGE VESSELS are more prone to turbulence
- FAST FLUID is more likely turbulent
- VISCOUS BLOOD is LESS turbulent
Describe the Law of Laplace
Tension = pressure*radius
- WALL TENSION INCREASES with Pressure and radius
- -> Elastic tissue in vessel wall helps BUFFER against high and low wall tension
Describe what happens to blood velocity as it passes through vessels
Flow = VELOCITY*CROSS SECTIONAL AREA
- -> FLOW IS CONSTANT
- -> VELOCITY DECREASES AS VESSELS DECREASE IN SIZE. (allows more time for blood, hormones, whatever to escape from capillaries)
