Term
| What are the two factors that determine blood flow through blood vessels? |
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Definition
-Pressure difference or pressure gradient or perfusion pressure- the force that pushes the blood through the vessel
-Resistance |
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Term
| How can flow through a vessel be calculated? |
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Definition
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Term
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Definition
| The quantity of blood that passes a given point in the circulation in a given period of time. |
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Term
| What does laminar or stream line flow refer to? |
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Definition
| Laminar or stream line flow is the tendency of the central most portion of blood to stay in the center of the vessel. |
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Term
| What effect does laminar flow have on the velocity of blood? |
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Definition
| Laminar flow causes parabolic profile of velocity within a blood vessel, with the velocity of blood flow highest in the center of the vessel and lowest toward the vessel walls |
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Term
| What are some conditions that may cause blood to become turbulent? |
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Definition
-when the rate of blood flow becomes too great
-when it passes by an obstruction in a vessel
-when it makes a sharp turn
-when it passes over a rough surface |
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Term
| Where is turbulence in blood more common--aorta or small vessels? |
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Definition
| Turbulence is more common in the aorta. |
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Term
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Definition
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Term
| What is Reynolds' number and how can it be measured? |
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Definition
Reynolds' number is the measure of the tendency for turbulence to occur.
Re= vdp/n
where
v= avg velocity of blood flow (cm/sec)
d= diameter of vessel (cm)
p=density
n=viscosity (in pose) |
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Term
| What are three functions of the aorta? |
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Definition
-distributes blood from the heart to the arterial system
-dampens the pulsatile pressure that results from the intermittent ejections of blood from the left ventricle
-acts as temporary blood storage vessel during each heartbeat to accommodate the ejected blood |
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Term
| What role do the large arteries (carotid, mesenteric, renal) play in the regulation of pressure and blood flow under normal physiological conditions? |
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Definition
| Under normal conditions the larger arteries have no significant role in the regulation of pressure and blood flow. |
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Term
| What is the function of small arteries and arterioles? |
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Definition
-distribute blood flow within the organs
-arterioles act as control conduits through which blood is released in the capillaries
-Are primary resistance vessels that regulate arterial blood pressure and blood flow w/in organs |
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Term
| What is the function of capillaries? |
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Definition
| Exchange of fluid, nutrients, electrolytes, hormones and other substances between blood and interstitial fluid |
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Term
| T/F Venules have smooth muscle. |
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Definition
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Term
| Where is there are large fall in the MAP? |
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Definition
| In the small arteries and arterioles. |
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Term
| What is the approximate MAP of blood when it empties from the venae cave into the right atrium? |
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Definition
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Term
| Where is the greatest volume of blood found? |
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Definition
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Term
| What units are used to measure resistance? |
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Definition
| Peripheral resistance unit which is mmHg/mL/sec found by dividing pressure by blood flow |
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Term
| What is the total peripheral vascular resistance or systemic vascular resistance? |
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Definition
| It is the resistance ot blood flow offered by all of the systemic vasculature, excluding the pulmondary vasculature. It is found using Ohm's law and under normal circumstances is about 1 PRU |
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Term
| Which has a lower total resistance, the systemic or pulmonary system? |
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Definition
| The pulmonary system has a lower total resistance of .14 PRU compared to 1 PRU of the systemic system. |
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Term
| What is the significance of the "fourth power law"? |
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Definition
| Poiseuille's law relates blood flow the radius raised to the fourth power, meaning that a small change in the diameter of the radius can lead to a large change in the amount of blood flow |
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Term
| In a series arrangement of vessels, what accounts for the drop in pressure? |
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Definition
| Resistance alone will account for pressure changes, b/c the amount of blood flow is constant |
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Term
| T/F. The total resistance of a network of vessels arranged in parallel is less than the resistance of the vessel the with the lowest resistance. |
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Definition
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Term
| What do multiple branches of vessels in parallel arrangement allow for? |
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Definition
| Allows tissues to regulate their own blood flow relatively independent of flow to other tissues. |
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Term
| What effect do parallel vessels have on resistance? |
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Definition
| Parallel vessels lower resistance. |
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Term
| What effect does lowering the temperature have on blood viscosity? |
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Definition
| A decrease in temperature increases viscosity by about 2% per degree centigrade |
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Term
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Definition
| A hematocrit above 40% which can double the viscosity of blood. |
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Term
| Why does blood viscosity increase further at low flow states, such as shock? |
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Definition
| During low flow states, cell to cell and protein to protein adhesions increase, which can cause erythrocytes to adhere to one another. |
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Term
| Why does an increase in arterial pressure lead to larger than expected increase in blood flow? |
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Definition
| B/c arterial pressure increases the force that pushes blood through and also causes blood vessels to distend, which decreases vascular resistance. |
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Term
| What is critical closing pressure? |
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Definition
| Critical closing pressure is the pressure at which flow ceases. |
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Term
| What effect does inhibition of the sympathetic nervous system have on blood vessel diameter? |
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Definition
| Inhibition of the sympathetic nervous system causes blood vessels to dilate and increases blood flow. |
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Term
| What effect does stimulation of the sympathetic nervous system have on blood vessel diameter? |
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Definition
| Sympathetic system stimulation constricts blood vessels and can decrease blood flow to zero. |
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Term
| How is the pulsatile output of the heart averaged into a more even pressure? |
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Definition
| Blood vessels are distensible and this allows them to accomodate the pulsatile output of the heart. |
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Term
| Which blood vessels are most distensible? |
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Definition
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Term
| What is vascular compliance or vascular capacitance? |
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Definition
| The total quantity of blood that can be stored in a given portion of vasculature for each millimeter of mercury pressure. |
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Term
| What happens to blood flow if the arteries become rigid? |
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Definition
| Blood flow ceases during diastole b/c the stroke volume could be stored during systole. |
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Term
| What are two major factors that affect the pulse pressure? |
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Definition
-stroke volume
-compliance of the arterial system |
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Term
| What is the nature of pulsation in the small arteries, arterioles, and capillaries? Why? |
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Definition
| THe intensity of pulsation is greatly decreased in the small arteries, arterioles, and capillaries, due to resistance and compliance. |
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Term
| What effect does arteriosclerosis have on arterial pressure? |
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Definition
| Arteriosclerosis hardens the arteries and thereby increases arterial pressure b/c they cannot stretch during systole. |
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Term
| What are the methods for measuring systolic and diastolic pressures? |
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Definition
-Directly- needles or catheters can be inserted into peripheral arteries of patients to measure arterial blood pressure using strain gages
-Indirectly-auscultatory method- blood pressure is estimated using a sphygmomanometer to measure brachial artery pressure. |
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Term
| T/F. Veins normally have a significant amount of basal tone. |
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Definition
| False. Compared with arterioles, veins normally have little basal tone. |
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Term
| Do vasodilator metabolites have a large or small effect on venous tone? |
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Definition
| Vasodilator metabolites have little effects on veins, b/c veins have little basal tones. |
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Term
| Which are more susceptible to physical influences, veins or arterioles? Why? |
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Definition
| Veins are more susceptible, b/c they have thinner walls. |
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Term
| What are some factors that can cause an increase in venous return? |
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Definition
-Increase in blood volume
-increase large vessel tone throughout the body with resultant increased peripheral venous pressures
-dilation of the arterioles, which decreases the peripheral resistance and allows rapid flow of blood from the arteries into the veins. |
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Term
| Does weakness of the heart increase or decrease right atrial pressure? Why? |
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Definition
| Weakness of the heart elevates right atrial pressure. B/c a weak heart is not going to be able to efficiently pump blood out of the right atrium and ventricle and into the lungs. |
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Term
| What regulates right atrial pressure? |
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Definition
-the ability of the heart to pump blood out of the right atrium and ventricle and into the lungs
-the tendency for blood to flow from the peripheral veins into the right atrium. |
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Term
| What is a normal value for right atrial pressure? What happens when pressure rises above this? |
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Definition
| A normal value is 0 mmHg. When atrial pressure rises above this blood backs up in the large veins. |
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Term
| Describe the venous pump. |
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Definition
| The venous pump is a system in the legs in which contraction of leg muscles forces blood through one way valves in the veins toward the heart. |
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Term
| What is the net effect of inspiration and expiration on right atrial pressure? |
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Definition
| During inspiration right atrial pressure falls and during expiration right atrial pressure increases, the net effects facilitates venous return. |
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Term
| What areas of the body are considered blood reservoir? |
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Definition
-the venous system is a blood reservoir
Specific blood reservoirs are:
-spleen
-liver
-large abdominal veins
-venous plexus beneath the skin |
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