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Phys Exam 2: Ch 15

Vascular distensibility

QuestionAnswer
What are the 3 fxns of vascular distensibility? (1) Allows for vasodilation (decreases resistance, increases local blood flow); (2) Accommodates pulsatile output of the heart; (3) Provides a venous reservoir fxn
How do you calculate vascular distensibility? Distensibility = (increase in volume)/(inc pressure x original volume)
Define vascular distensibility The amount of potential stretch of a vessel
Which is more distensible: arteries or veins? How much more are these distensible? Systemic veins are ~8 times are more distensible than systemic arteries
Define vascular compliance Volume change in response to a given pressure,or (change in volume)/(change in pressure)
How do you (simply) calculate compliance? Compliance = Distensibility x Volume --> OR change in volume/change in pressure
Since veins are more compliant than arteries, what does this say for the relationship of volume change and pressure change? There is a greater volume change for a given pressure change
What does sympathetic stimulation do after severe hemorrhage? Maintain arterial pressure --> you can bleed a lot and still maintain blood pressure
Describe arterial pressure pulses (1) Allow continuous pressure to the capillaries despite a pulsatile heart output
Arterial pressure pulses - fill in the blanks: The __ the stroke volume, the __ the pressure pulse in the aorta Greater, Greater
Arterial pressure pulses - fill in the blanks: The __ the arterial compliance, the __ the the aortic pressure increase for a given stroke volume Greater, Smaller; (i.e. the more the artery stretches, the smaller the pressure pulse increase)
Fill in the blanks: in the aorta, pressure __ during systole and __ during diastole Increases, declines
Define the incisura on the aortic pressure pulse graph The notch; the back pressure when the aortic valves close
What helps propel blood thru the remaining arteries? Aortic compliance and recoil
What is arteriosclerosis? The aortic wall is stiff and resistant to stretching (i.e. vessel is no longer compliant, so pressure increases in the aorta)
What is aortic stenosis? Narrowing of the aortic valve opening, so less blood enters - aortic pressure pulse graph almost completely loses its notch/incisura
What happens with a patent ductus arteriosus? Allows much of the left ventricular stroke volume to go into the pulmonary artery & lung, so less blood remains in the aorta and its diastolic pressure drops below normal (lung BP increases)
What happens with aortic regurgitation? Occurs when the aortic valve fails to close, allowing aortic pressure to drop below normal, and the next stroke volume to be larger than normal (lung BP increases) - no notch/incisura in the aortic pressure pulse graph
What happens to the pressure pulse peripherally, and what is this called? As the pressure pulse extends peripherally, the combined resistance and compliance reduce the pulse --> progressive damping of the pressure pulse
Peripheral reduction of the aortic pressure pulse - fill in the blanks: The __the resistance of the arterial vessels (length, small diameter), the more the pressure pulse is __. Greater, reduced
Peripheral reduction of the aortic pressure pulse - fill in the blanks: The __the compliance of the arterial vessels (the ability to increase in volume w/increase in pressure), the more the pressure pulse is __. Greater, reduced
What determines central venous pressure? Right atrial pressure
What can decrease atrial pressure (this central venous pressure)? (1) Exceptionally vigorous heartbeat; (2) Severe hemorrhage (lower limit is ~ -5mmHg
What can increase atrial pressure (this central venous pressure)? (1) heart muscle weakness; (2) increased blood volume; (3) Increased muscle tone of large veins; (4) dilation of the arterioles (the upper limit is ~20-30mmHg
What can increase venous resistance? (1)Increased R atrial pressure; (2)Anatomical compression; (3)Abdominal Pressure; (4)Gravity, or hydrostatic pressure
What can increase R atrial pressure? usually heart failure or too large a transfusion
How does anatomical compression increase venous resistance? (a)veins from the arms crossing the first rib; (b) veins from the lower body compressed by abdominal organs; (c)veins in the neck compressed by atmospheric pressure
What can increase abdominal pressure? (1) Pregnancy; (2) Excessive fluid (kidney failure or liver cirrhosis); (3) A very large tumor
What are the effects of gravity on venous pressure? (1) blood in the feet when standing has ~90mmHg to overcome to return to the heart; (2) veins in the neck collapse; (3) venous pressures in the dural sinuses are negative (the skull cannot collapse)
What will force the blood toward the heart, especially from the lower body? Contraction of the muscles surrounding a valve, compressing the valve
What are varicose veins? Excess venous pressure (from standing long-term or pregnancy) stretches the veins so that the valves no longer hold, so more blood pools in the legs
What is the volume of the venous reservoirs in (each) of the large abdominal veins, liver sinuses, and venous plexus under the skin? ~200-300 mL
What is the volume of the venous reservoirs in (each) of the lungs, heart, and spleen? ~50-200 mL
Created by: hclark86
 

 



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