A & P Test Four - 7.12

Question	Answer
How can venous system increase cardiac output when needed?	When veins are constricted, large quantities of blood are transferred to the heart, thereby increasing cardiac output.
Venous tone equals	venous distensibility
What is distensibility?	The ability of a blood vessel to stretch. This allows the veins to accommodate pulsatile flow from the heart. Provides flow even through the smallest vessels.
What is vascular compliance?	The total quantity of blood that can be stored in a given portion of the circulation for each mmHg of pressure. It is the ability of vessel to stretch and hold volume.
How do you calculate compliance?	Distensibility X Volume = Compliance The compliance of veins is 24 times that of arteries.
How do distensibility and compliance differ?	Distensibility describes the characteristics of the veins. The compliance is a measurement of the quantity of blood that can be stored in the circulation. Compliance considers volume as well as distensibility.
How do you calculate pulse pressure?	Systolic pressure - Diastolic pressure
What's another name for an incisura? What is an incisura?	The dicrotic notch. Produced when the aortic valve closes.
How does stroke volume affect pulse pressure?	When stroke volume increases, this increases pulse pressure. If stroke volume decreases, this decreases pulse pressure.
How does pulse pressure affect arterial compliance?	Decrease in compliance results in an increase in pulse pressure. An increase in compliance decreases pulse pressure.
What is the mean arterial blood pressure?	The driving force for the blood flow in the arteries.
What is mean arterial pressure more influenced by? Diastolic or systolic pressure?	Diastolic pressure
What are the most distensible vessels? How much more distensible are they?	Veins. They are eight time more distensible.
What is vascular tone?	Vascular smooth muscle is normally in a semi-contracted state.
Describe the nature of driving pressure in a rigid tube.	A rigid tube has a linear relationship between driving pressure and flow.
Describe the nature of driving pressure in a distensible tube.	The relationship is non=linear. As pressure inside the tube increases, the size (radius) of the tube also increases, thus meaning the walls are distended.
What is the relationship of resistance and flow in a distensible tube?	Resistance decreases with an increase in flow. Small, distensible vessels exposed to high pressures will exhibit less resistance to flow than at normal pressures.
What is the Law of LaPlace?	Tension is a measurement of pressure. Wall tension is proportional to radius. Tension is the internal force generated by a structure. The formula is T = P X R. T is wall tension, P is pressure of the fluid within the cylinder and R is the radius of the tube.
What are the consequences of LaPlace's Law with respect to the diameter of cylinders.	To withstand the same internal pressure, a large-diameter cylinder must have thicker walls than a small-diameter cylinder
What types of vessels are most likely to rupture?	Larger-radius vessels are more likely to rupture because they have higher wall tension. Examples include an abdominal aortic aneurysm.
How does the Law of LaPlace apply to the filing pressure of the left ventricle?	The tension in the ventricular wall increases as filling increases
Is MAP lower downstream or upstream?	It is lower downstream. Systolic pressure is higher in larger arteries than in aorta.
Damping and loss of pulse pressure is directly proportional to what?	Resistance and compliance. The greater the resistance, the more difficult it is to transmit pulse pressure. The greater the compliance, the greater the damping of the pulse pressure.
Describe how arteriosclerosis affects pulse pressure.	Arteriosclerosis Vessels become less compliant Pulse pressure increases to nearly twice normal
How does aortic stenosis affect pulse pressure?	Aortic Stenosis Aortic valve opening decreased There is diminished blood flow thru the valve So the pulse pressure is significantly decreased
How does a patent ductus arterioles affect pulse pressure contours?	Patent ductus arteriosus Major portion of blood pumped into aorta from left ventricle flows backward thru the open ductus arteriosus into pulmonary artery and lung circulation Diastolic pressure falls very low before the next heartbeat
How does aortic regurgitation affect pulse pressure?	Aortic Regurgitation Aortic valve incompetent —does not close completely or may be absent Blood pumped from left ventricle flows immediately back into left ventricle Aortic pressure can fall all way to zero between heartbeats No dicrotic notch either
Name the value of widened pulse pressure.	Greater than 40 mmHg
What are the causes of widened pulse pressure?	Isolated systolic hypertension – Aortic regurgitation – Thyrotoxicosis – PDA – Aortic coarctation – anemia
What is the value for narrowed pulse pressure?	Less than 30 mmHg
What are some causes of narrowed pulse pressure?	– Tachycardia – Severe aortic stenosis – Constrictive pericarditis – Pericardial effusion – ascites
How do you calculate MAP? What are the normal values for MAP?	MAP – [(2 x diastolic) + systolic] / 3 • Diastole counts twice as much as systole because 2/3 of the cardiac cycle is spent in diastole • MAP of ~ 60 mmHg required to perfuse coronary arteries, brain, kidneys • Usual range is 70 to 110 mmHg
What is another name for central venous pressure?	Right atrium pressure
What factors increase Right Atrial Pressure?	• Factors that increase RAP: - increased blood volume - increased venous tone - dilation of arterioles - decreased cardiac function
How are the veins inside the skull affected in regards to central venous pressure?	• veins on inside of skull are negative pressure b/c they are in noncollapsible chamber • Problem occurs during craniotomy and opening of sagittal sinus • Can suck in air leading to a venous air embolus (VAE)

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A & P Test Four - 7.12

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	Created by Rachel Nall almost 8 years ago