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Phys Exam 2: Ch 15
Vascular distensibility
| Question | Answer |
|---|---|
| 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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