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Spi chapter 18
Hemodynamics
| Question | Answer |
|---|---|
| What is Hemodynamics? | The study of blood moving through the circulatory system |
| What is flow? | Indicates the volume of blood moving during a particular time |
| Flow is also called | volume flow rate |
| Flow unit: | Volume divided by time |
| What is velocity? | Indicates the speed or swiftness of a fluid moving from one location to another |
| Velocity units: | Distance divided by time |
| Three basic forms of blood flow are: | Pulsatile Phasic Steady |
| What is Pulsatile flow? | Occurs when blood moves with a variable velocity |
| What is cardiac contraction? | Blood accelerates and decelerates |
| Pulsatile flow also appears in: | the arterial circulation |
| What is Phasic flow? | Occurs when blood moves with variable velocity |
| What occurs when blood accelerates and decelerates? | Respiration |
| Phasic flow also appears in: | Venous circulation |
| What is Steady flow? | Occurs when a fluid moves at a constant speed or velocity |
| What is an example of steady flow? | Water flowing through a garden hose |
| Steady flow is present in: | Venous circulation when individuals stop breathing for a brief moment |
| What is Laminar flow? | When the flow streamlines are aligned and parallel. It is silent flow |
| The word lamina also means: | layer |
| Laminar flow is characterized by: | layers of blood that travel at individual speeds |
| Laminar flow patterns are commonly found in: | normal physiologic states |
| What are two forms of laminar flow? | Plug & Parabolic flow |
| Plug flow is: | occurs when all the layers of blood cells travel at the same velocity |
| Parabolic flow is: | Has a bullet shaped profile and velocity is the highest in the center of lumen & decreases to its minimum at the vessel wall |
| What predicts whether flow is laminar or turbulent? | Reynolds number |
| Reynolds number for laminar flow is: | Less than 1,500 |
| What is turbulent flow? | Characterized by chaotic flow patterns in many different directions and speeds |
| Small hurricane like, swirling, rotational patterns are known as? | eddy current or vortex |
| Turbulence is often associated with: | Cardiovascular pathology & elevated blood velocities |
| Turbulence converts flow energy into: | Other forms such as sound and vibration |
| Sound associated with turbulence is called: | murmur or a bruit |
| Tissue vibration associated with turbulence is called a: | thrill |
| Reynolds number for turbulent flow is: | Greater than 2,000 |
| Energy gradient is: | Blood moves from regions of higher energy to lower |
| What provides energy to the circulating blood? | Contraction of the heart during systole |
| Energy associated with blood are: | Kinetic Pressure Gravitational |
| Kinetic energy is associated with: | a moving object |
| Two factors that determine kinetic energy are: | An objects mass & the speed at which it moves |
| Pressure gradient is a form of: | stored or potential energy |
| How is pressure a major form of energy? | Circulates blood and creates flow by overcoming resistance |
| Gravitational energy is form of: | stored or potential energy |
| Gravitational energy is associated with: | an elevated object |
| Three forms of Energy Losses in Circulation: | Vicious, frictional & inertial loss |
| Viscosity describes: | thickness of a fluid |
| More energy is lost with | movement of high viscosity fluids |
| Viscous loss is associated with: | blood overcoming its internal stickiness |
| Viscosity unit is | Poise |
| Viscosity energy loss in blood is determined by | the hematocrit |
| Hematocrit is | the percentage of blood made of red blood cells |
| Normal value of blood is | 45% |
| Frictional losses: | Occur when flow energy is converted to heat as one object rubs against another |
| Inertia relates to: | the tendency of a fluid to resist changes in its velocity |
| Inertial energy loss occurs during which three events? | Pulsatile flow, phasic flow and velocity changes at a stenosis |
| Velocity increases as: | the vessel narrows |
| Velocity decreases as: | blood flows out of the stenosis into a vessel segment of normal diameter |
| What is stenosis? | a narrowing in the lumen of a vessel |
| In post stenotic turbelence: | the lumen expands more dramatically than the streamlines of blood are able to fill it |
| Effects of a stenosis are: | Change in flow direction Increased velocity as vessel narrows Turbulence downstream from the stenosis Pressure gradient across the stenosis Loss of pulsatility |
| What is Bernoulli Principle? | Describes the relationship between velocity and pressure in a moving fluid |
| What is Conservation of energy? | With a steady flow, the sum of all forms of energy is the same everywhere |
| Where is the pressure lowest, at location A, B or C? | Location B (the stenosis) |
| At location C: | Blood slows (turbulence) |
| Formula for flow, resistance & pressure gradient is? | Pressure gradient= flow x resistance |
| Pressure gradient increases when either: | Flow increases, or resistance increases |
| Flow increases when either: | Pressure gradient increases or resistance decreases |
| Formula for Ohm's Law: | voltage= current x resistance |
| Pressure in a fluid system is called: | Voltage in an electrical system |
| Flow in a fluid system is called: | current in a electrical one |
| Resistance has what the same in both systems? | Name |
| Electrical resistance is reported in units of: | Ohms |
| In the circulatory system, the resistance vessels are called? | Arterioles |
| What is the typical resistance of veins? | Low resistance |
| How do veins adapt to increase flow during exercise? | Normal veins increase flow with only a small increase in pressure |
| What is hydrostatic pressure? | Pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level |
| Hydrostatic pressure unit: | mmHg |
| Normal pressure measurements are taken at : | the level of the heart |
| What is supine? | Flat on your back |
| What is the hydrostatic pressure at supine position? | zero everywhere |
| At locations below heart level, hydrostatic pressure is: | postive |
| At locations above heart level, hydrostatic pressure is: | negative |
| Measured pressure formula: | measured pressure=circulatory pressure + hydrostatic pressure |
| What is inspiration? | diaphragm moves downward towards abdomen |
| What is expiration? | diaphragm moves upwards into thorax |
| Inspiration pressure: | Thoracic pressure decreases Abdominal pressure increases |
| Expiration pressure: | Thoracic pressure increases Abdominal pressure decreases |
| Inspiration venous: | Venous return to the heart increases Venous flow in legs decrease |
| Expiration venous: | Venous return to the heart decreases Venous flow in legs increases |
Created by:
Montesmayan