Lecture 9: Circulation Flashcards
What is systolic pulmonary artery pressure?
25 mmHg
What does systemic capillary pressure range from?
35 mmHg-10 mmHg
35 mmHg when entering from arterioles
10 mmHg when leaving through venules
What is pulmonary diastolic pressure?
8 mmHg
What percentage of blood volume is in systemic circulation?
84%
What percentage of blood volume is in the veins?
64%
What percentage of blood volume is in the arteries?
13%
What percentage of blood volume is in the arterioles and capillaries?
7%
What percentage of blood volume is in the heart and lungs?
16%
What does it mean to say “the velocity of blood flow is INVERSELY proportional to vascular cross-sectional area”?
If cross-sectional area increases, velocity decreases
T/F: V=F/A means if F increases, V increases
True
What are the 3 basic principles underlying all functions of the circulatory system?
1) Rate of blood flow to each tissue is precisely controlled in relation to tissue need
2) Cardiac output is controlled by the sum of all local tissue flows (heart will pump out what tissues need)
3) Arterial pressure regulation is independent of local blood flow control or cardiac output control
What does functional principle 1 of circulatory system mean?
Microvessels control tissue needs by acting on local blood vessels and dilating/constricting them
What does functional principle 2 of circulatory system mean?
Heart responds to demands of tissue
Nerve signals may be needed to help heart pump required amount of blood
What does functional principle 3 of circulatory system mean?
If arterial pressure drops below 100 mmHg, nervous reflexes…
Increase force of heart pumping
Constrict large venous reservoirs
Constrict most arterials throughout body
What is flow proportional to?
Directly proportional to pressure difference
Inversely proportional to resistance
What is the overall blood flow of an adult at rest?
5,000 ml/min
What is laminar flow?
Layered blood flow that flows in a steady state
T/F: Laminar blood flow equals streamline flow
True
T/F: Velocity of blood flowing near vessel walls flows quicker than blood flowing near center of vessel
False, blood flowing in center of vessel flows quicker than blood flowing near vessel walls
When does turbulent flow occur?
When…
Flow is too great
Blood passes obstruction
Blood makes sharp turn
Blood passes rough surface
What is another term for turbulent flow?
Eddy current
What is Reynolds Number (Re) a measure of?
Tendency for turbulence to occur
What is Reynolds Number directly proportional to?
Velocity
Vessel diameter
Density
What is Reynolds Number indirectly proportional to?
Viscosity
At what Re number will turbulent flow occur in some regions?
When Re is above 200-400
At what Re number will turbulent flow occur in straight vessels?
When Re is above 2,000
What is the definition of blood pressure?
Force exerted by blood against any unit area of the vessel wall
What is the definition of resistance?
Impediment to blood flow
How do you calculate systemic resistance?
Cardiac output/Pressure difference from systemic arteries to systemic veins= _____PRU
CO=100 ml/sec
P=100 mmHg
Resistance=100/100=1PRU
When vessels are highly constricted, PRU may rise to what?
4 PRU
When vessels are dilated, PRU may fall to what?
PRU 0.2
How do you calculate resistance in pulmonary system?
(Pulmonary arterial pressure-Left atrial pressure)/Cardiac output=_____PRU
*Cardiac output does not ∆ b/w pulmonary & systemic circulation
AP=16 mmHg
LP=2 mmHg
CO=100 ml/sec
Resistance=14/100=0.14PRU
What is the definition of conductance?
Measure of blood flow through a vessel for a given pressure difference
It is the exact reciprocal of resistance (1/resistance)
T/F: Blood vessels arranged in series have a total resistance much less than the resistance of any single blood vessel.
False, blood vessels arranged in PARALLEL have a total resistance much less than the resistance of any single blood vessel
Does amputation or removal or an organ increase or decrease total peripheral resistance?
Increase
How much higher is blood viscosity than water, and why is that the case?
3x higher because of the RBC’s
What is polycythemia?
Having a hematocrit around 60-70
What is anemia?
Having a hematocrit around 10
If there are more RBC’s in the blood, the viscosity will be _______.
Greater
What is autoregulation?
Ability for tissues to adjust vascular resistance through changes in arterial pressure between 700-175 mmHg
What happens when autoregulation drops below 75?
It becomes very tough to keep blood flow going
What happens when autoregulation gets below 50?
Blood flow ceases
