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Phys Exam 2: Ch 14
Physics of Circulation
| Question | Answer |
|---|---|
| How is blood flow measured? | Flow = change in pressure/resistance --> measured in mL/min or L/min |
| What is laminar flow? | Flow pattern marked by smooth changes in pressure & velocity (SMOOTH!) |
| What is turbulent flow? | Flow pattern that includes irregular variations in pressure & velocity (NOT SMOOTH!) |
| What is Reynolds Number (Re)? | A measure of turbulence |
| What causes Re to increase? | Velocity of flow, vessel diameter increases, decreased viscosity |
| What causes Re to decrease? | Increased viscosity |
| What does a high (~200-4000+) Re value indicate? A low (0-~100) Re value? | Turbulence; laminar flow |
| Define BP | Force of blood against the blood vessel wall, measured in mmHg |
| How do you calculate Reynolds Number (Re)? | Re = (velocity of flow x diameter of vessel) / kinematic viscosity [n/p] |
| Define Resistance | The force that must be overcome for the blood to flow |
| How do you calculate Resistance? | R = change in pressure/flow |
| If you have Arterial-venous pressure difference = 100mmHg and Cardiac output 100mL/sec, what is the Peripheral Resistance Unit? | 100mmHg/100mL/sec = 1 PRU |
| How do you calculate PRU? | PRU = (AV pressure difference)/Cardiac output |
| What is the typical range of PRU? | 0.2 (extreme vasodilation) to 4 (vasoconstriction) |
| If you have a pulmonary pressure differential is 14mmHg, what is PRU? | 14mmHg/100mL/sec = 0.14 PRU |
| What is the resistance of the entire systemic circulation? | 100mmHg/100mL/sec |
| What is conductance? | The measure of blood flow for a given pressure distance (i.e. the inverse of resistance) |
| GHow do you calculate conductance? | Conductance = 1/Resistance |
| What is the take away message from Poiseuille's Law? | As the radius of the blood vessel increases, the flow of blood quadruples |
| What is the effect of blood vessel diameter on blood flow? | Flow increases as the 4th power of the radius of the vessel (i.e. increases 4-fold) |
| What is hematocrit? | The % of blood that is RBCs |
| What happens if the hematocrit increases? | Blood viscosity increases |
| How does blood doping lead to heart attacks? | Increasing the % of RBCs (hematocrit) increases blood viscosity |
| What happens as the % of blood cells in a volume of blood increases? | The viscosity increases, resistance to flow increases |
| How many circulatory systems exist in the body? | 2 - pulmonary circulation and systemic circulation |
| What are the 3 principles of control of the circulation? | 1. the rate of blood flow to a tissue is based on the need of that tissue; 2. Cardiac output is based on venous return; 3. Arterial pressure is controlled independently of either local flow or cardiac output |
| Why is it important that rate of blood flow to a tissue is based on that tissue's needs? | Because not all of the tissues need the same blood flow supply at one time |
Created by:
hclark86
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